FIELD

The present invention is related to a Fiber Coupled Integrating Sphere (FCIS) Based- Laser Energy Meter and Calibration System (FCIS based-LEMCS), designed for both measuring the averaged pulse energy of a Pulsed Type Laser Source generating infinite laser pulse train in time domain, and calibrating Commercial Laser Energy Meters, which is fully traceable to Primary Level Standards, together with new calibration method.

BACKGROUND

Laser, an acronym, means amplification of amplitude-, frequency- and phase-coherent electromagnetic waves generated by a suitable pumping process inside a closed region composed of a mixture of relevant radiating atoms and molecules, the energy levels of which fully conforms to a stimulated emission created by a feedback of some portion of the coherent electromagnetic wave at the output port of the region.

The areas of use of lasers get very diverse along with the increasing in the developments of the design and manufacturing of high technology products. If a categorization according to priorities of using the highest technology in industrial products is made, it is seen that health and war technology equipments are more dominant over the other industry sectors. The lasers can have continuous wave (CW) mode lasing and/or pulsed-mode lasing and have conspicuous and effective characteristics such as lethal or non lethal effects, physiological, psychological or directly physical effect depending on the energy transferred into any target in modern war and health equipments. In order to make exact and correct evaluations about the resultant effects of any laser source on any target, it seems that it is an unavoidable approach to make spectral power distribution, total power and energy measurements of the relevant laser source in addition to the determination of surface absorption/reflection, structural and atomic/molecular bonding characteristics of the target.

The spectral power distribution (W/nra) and the total power (W) carry a significant meaning for a CW mode/regime laser source because the knowledge of total power of a CW laser is enough to calculate the total exposure over time t (s) for surface of any relevant target in (J) and (J/cm ² ), energy density, by taking the target absorptiveness into account. Differently from the measurement of total power of CW laser in W, the measurement of laser energy (J) per pulse for a Pulsed Type Laser Source in time domain conveys a significant meaning, because the exposure of the Pulsed Type Laser Source depends on pulse width (PW) and peak power Po of the Pulsed Type Laser Source, considering surface absorption/reflection, structural and atomic/molecular bonding properties of the target

NOTE: The term "Chopped Type Laser Source" in the invention means the modulated laser source generated by chopping CW Gaussian Laser Beams of CW Laser Source(s) mechanically by means of the group of the circular and metallic choppers, which is strict a part ofFCIS based-LEMCS invented. The term "Pulsed Type Laser Source" in the invention means any other laser source which is different from the "Chopped Type Laser Source", and which is not a part ofFCIS based-LEMCS invented. Nevertheless, both "Chopped Type Laser Source" and "Pulsed Type Laser Source" in the invention produce laser pulses, both of which have Gaussian beam profile, as infinite pulse train in time domain and finally, the term "Gaussian Laser Beam" used in the invention means diffraction limited - transverse electromagnetic mode having the lowest order (TEMoo).

The transferred energy into the target by a laser source regardless of CW or pulsed type results in a temperature increase in limited volume of the target, depending on the heat capacity, mass and the initial temperature of the relevant volume of the target. Detecting the temperature increase of the relevant volume of the target resulted from the energy of the laser source can be made via conventional semiconductor type or metal/metal contact type temperature sensors. To gain signal to noise ratio (SNR) of detection system, which is one of the most important parameter increasing the measurement uncertainty, the separation of the temperature variation caused by energy transfer requires to be extended. The way to extend the separation between the initial temperature and the final temperature caused by laser source energy is to reduce the heat capacity (specific heat) of the target which is accomplished by reducing the initial temperature of the target down to cryogenic level, relying on Bose-Einstein approach. Reducing the initial temperature of the target also minimizes the atomic and molecular vibrations. According to Bose-Einstein statistic for the canonical ensemble, the heat capacity (specific heat) of a solid target reduces exponentially at cryogenic levels of temperature and this physical phenomenon expands the separation between the final and the initial temperature of the target, which expresses an absorbing cavity in a Cryogenic Radiometer (CR) and finally a calorimetric measurement for absolute optical power measurement and also optical energy measurement.

By considering the above summary, the traceable measurements of the laser energy meters and their traceable calibrations can be carried out by measuring the temperature difference (K) between the final and the initial temperature of the target along with inclusion of mass (kg) and the specific heat (J/(kg K)), which is a measureable quantity, in the calculations, bearing in mind that the time constant of the target (or the absorbing cavity). In a CR, the specific heat of the absorbing cavity for the electrical watt (A.V=W) applied within At (s) time interval is obtained as a ratio and it is called as thermal coefficient in (W/K), also generating (J/K). In this traceability stage, it is seen that temperature (K), direct current (A) and direct voltage (V) together with traceable time (s) measurement necessary to define the time constant (s) of the target (or the absorbing cavity) and time interval At (s) of the electrical power applied to the absorbing cavity should be wholly traceable to primary standards. As a result, the averaged pulse energy of a Pulsed Type Laser Source / Chopped Type Laser Source can be derived by calorimetric methods with traceability of temperature (K), direct current (A), direct voltage (V), and time (s).

Under the illumination of the above briefing related to the traceability chain of optical power and energy, it is understood that we need an optical power measurement in (W) and a time measurement in (s) for realization of the averaged pulse energy (J) of any Pulsed Type Laser Source. The mathematical basis belonging to deriving the averaged pulse energy of the Pulsed Type Laser Source is given by taking the laser pulses having a pulse width of PW (s) and a period of T (s), the peak power of which is Po (W), as an infinite pulse trainin time domain. Referring to the periodic pulse shape of Pulsed Type Laser Source in the style of an infinite pulse wave train, the function of output power of the Pulsed Type Laser Source for a period of T (s) is defined as P(t) in Eq.(l):

p _{M = {} Po 0 < t < PW

L ^{J 1} 0 PW < t < T ^{L J L J}

And P(t) is a periodical function, as an infinite laser pulse train in time domain, P(t)=P(t+T). Pulse energy of the single pulse of Pulsed Type Laser Source, PE (J);

PE = P ₀ . PW (J) (2)

The average power of the Pulsed Type Laser Source, P _av ;

Pav = <PM ) = i jJ P(t) dt (W) (3)

If the integral is written in the most general form and in the averaged terms by taking the Duty Cycle into account, Eq.(4) is obtained:

Pav = ^ P ₀ (W) (4)

Duty Cycle _av = _{Tav = PWay + DTay (5)}

¹ av

Pav ^ PEav (W) (6)

¹ av

Where the averaged pulse width is PW _av and the averaged dead time is DT _av in an averaged repetition period T _av for an infinite laser pulse train generated by Pulsed Type Laser Source. The averaged pulse energy of Pulsed Type Laser Source is obtained by multiplying N with PE _av . N is the pulse number and is equal to 1 for periodic and infinite pulse train in time domain. Eq.(4) and (6) give us a very useful approach to derive the averaged pulse energy PEav of Pulsed Type Laser Source. If repetition period T and the averaged optical power Pav of Pulsed Type Laser Source are measured, the averaged pulse energy can easily be calculated. These measurements of the averaged repetition period T _av and the averaged optical power P _av should be performed traceable to primary level standards, which are ¹³³ Cs (or ⁸⁷ Rb) Atomic Frequency Standard in time scale (s), and optical power transfer standard calibrated against absolute optical power measurement system called CR in optical power scale (W) [1 and 2], and an electrometer in direct current scale (A) traceable to Quantum Hall System, and DC Josephson System. The precise measurements of T _av and P _av traceable the primary level standards exhibits a process without measuring the temperature change caused by the averaged pulse energy of a Pulsed Type Laser Source. The most uncertainty contribution of the calorimetric measurements of the averaged pulse energy is resulted from the determination time constant of an absorbing surface (target) and so the pulse and the modulation response of the absorbing cavity (target). In addition to the elimination of time constant of FCIS in time/frequency related measurements in the invention, the new configuration of the integrating sphere invented, called as FCIS, enables the user positioning the laser beam having a Gaussian profile on the same optical axis with respect to the entrance port for every calibration process so the reproducibility of the calibration and the measurement processes are increased with the new configuration of FCIS.

Photovoltaic type photodiodes generate an integrated photocurrent as response of the optical flux falling on the sensitive surfaces, corresponding to average optical power of the incident optical flux. This is also valid for the ultra fast photodiodes having very fast impulse response, like positive-intrinsic-negative (PIN) photodiodes as well as avalanched type photodiodes supplied with a reversed voltage bias which reduces the diffusion capacity of the photodiode, still used in optical time domain reflectometer instruments. The integrated photocurrent is also generated for the relatively small portion of light flux within optical pulses having ultra short time intervals, such as At≡20xl0- ¹² s.

The parameters to be measured to determine the averaged pulse energy PE _av of the Pulsed Type Laser Source in Eq.(6) are averaged repetition period T _av , number of pulses N having a varying pulse width PW, and average power P _av , corresponding to an average photocurrent I _av generated by the First Photodiode, which is InGaAs_l for the apparatus designed as a preferred embodiment in the invention. Eq.(6) can be re- written as Eq.(7) by considering the spectral responsivity of the First Photodiode in order to obtain the averaged pulse energy of Pulsed Type Laser Source in Fig.l and Fig.2.

Pav = ^ = PEav (W) (7)

^K FCIS ¹ av

Where Rpcis * ^{s tne} spectral power responsivity of FCIS, to which the First Photodiode is mounted, in A/W. As stated above, I _av is measured by the First Photodiode placed orthogonally with respect to laser entrance port of FCIS. I _av = (I _p h(t)), I _p h(t) = I _p h(t + T) is the periodic pulse type photocurrent, generated by P(t). I _av is the time average of Iph(t) = I _pho rect(t). T _av (and/ or f _av ) is measured by using a second photodiode mounted on a small steel hemisphere, which is placed on directly opposite Gaussian laser beam entrance port of FCIS of FCIS based-LEMCS. For single pulse having a unit amplitude, rect(t) function is defined as in Eq.(8).

. _{f (} 0 PW < t <∞

r ^{ectM = {} i 0 < t < PW ^{} (8)}

This definition of a single pulse given in Eq.(8) will be useful for the description of the pulse response of the First Photodiode and for the description of use of a second photodiode, which is different from the First Photodiode, and which has a relatively small time constant, to carry out time/frequency related measurements in Eq.(7). Rpcis in Eq.(7) is obtained by calibrating FCIS based-LEMCS against the Optical Power Transfer Standard, which is an InGaAs based spectralon sphere radiometer directly and which is absolutely calibrated against Cryogenic Radiometer (CR) in this invention. Another alternative process of deriving the Rpcis °f the First Photodiode can be performed with a relatively higher uncertainty arising from the surface non uniformity by referencing a flat spectral response Electrically Calibrated Pyroelectric Radiometer (ECPR), traceable to CR, in such a way that the whole spectra of 900 nm to 1650 nm of the First Photodiode is covered.

NOTE: The use of different type of Optical Power Transfer Standard doesn't disturb the philosophy of the invention because FCIS based-LEMCS is a preferred embodiment.

According to Eq.(7), if I _av , T _av , and Rpcis ^are measured, the specified and averaged pulse energy PE _av of the Pulsed Type Laser Source can be calculated with an expanded uncertainty by taking the related partial derivations of I _av , T _av and Rpcis ^mto the calculations.

The Second Photodiode, which is InGaAs_2 in the invention as a preferred embodiment, is assembled with a first multimode (MM) patch cord. FC/PC connector end of the first multimode (MM) patch cord is combined to a Mechanical Attenuator and the HMS connector end of the first MM fiber patch cord having a Zr ferrule is mounted on the center of the inner wall of a small hemisphere, which is placed inside FCIS, which has a smaller diameter than that of FCIS. The Second Photodiode combined with the hemisphere through a second MM patch cord, the Mechanical Attenuator, and the first MM patch cord having ceramic and Zr ferrules is used for the time measurements such as averaged repetition period T _av and averaged repetition frequency f _av in Eq.(7), cutoff limit is 6 GHz. The second use purpose of the Second Photodiode is to coincide optical axes of FCIS and Pulsed Type Laser Source, Chopped Type Laser Source, and CW Laser Source. The Small Steel Hemisphere is made from stainless steel and is assembled with a Zr ferrule of the first MM optical fiber patch cord. The small steel hemisphere is so settled inside FCIS that Gaussian laser beam entrance port of FCIS of FCIS based-LEMCS sees directly the center of the Small Steel Hemisphere, at the center of which Zr ferrule of HMS connector end of the first MM optical fiber patch cord is mounted back 0.2 mm from the inner surface. The placement of a steel hemisphere together with Zr ferrule of HMS connector end of the first MM optical fiber patch cord is one of the important points of this invention.

The practical way to search the frequency response of any electronic device, such as a pin photodiode in this invention, is to apply a pulse having a varying pulse width and a varying period to the electronic device. According to the Fourier transformation between time and frequency domains, as long as the pulse width PW is made relatively narrow, it is seen that the frequency content of the pulse increases. As a result, an ideal 5(t) -impulse function in time domain covers a frequency range from zero to infinite theoretically. The periodic optical pulses P(t) generated by the Pulsed Type Laser Source, the pulse width PW of which are adjustable, can be defined as a sum of odd (sinus) harmonics in Fourier series, and they have the decreasing amplitude with a DC component, the period of which is T (s), matching the repetition frequency f (Hz). Correspondingly, the modulation frequency response of FCIS is obtained the sum of all the responses of FCIS through the First Photodiode against the each frequency component obtained from the Fourier series. When the frequency content of Fourier Series of a periodic pulse train repeated within repetition period T is seen, the first term, which has the highest amplitude, is f (Hz), which is exactly the same as the repetition frequency of the Pulsed Type Laser Source. The successive frequency terms of sinus are lined up to 2f, 3f, 4f,....,nf, where n is the number of the summed frequency components, with the decreasing amplitude. It should be noted that making the pulse width PW in time domain be narrow increases the frequency contents. Therefore the pulse response characteristics and the modulation frequency response characteristics of the First Photodiode of FCIS, which is used to measure the averaged photocurrent I _av proportional to the averaged optical power P _av , are presented together herein.

It is pointed out that FCIS based-LEMCS and the method described in the invention can operate up to a repetition rate of 1 MHz which is the cutoff limit of the First Photodiode. In order to use FCIS based-LEMCS correctly and properly in measuring the average optical power P _av , FCIS based-LEMS should be held within the frequency range in which the First Photodiode of FCIS based-LEMCS has a flat frequency response. If the repetition frequency is too high the First Photodiode to catch, which corresponds to being too faster rising and falling edge times, and too narrower pulse widths and dead times, it is impossible to convert the average optical power of such an infinite pulse train of Pulsed Type Laser Source having a peak power of Po into the average photocurrent. This is an inherent behavior for the photodiodes as well as the electronic circuit exhibiting low pass filter behavior.

The First Photodiode behaves as a RC low pass filter for the increasing modulation frequencies resulted from the equivalent circuits composed of the total of junction capacitance ( ) and stray capacitance (C _s ) of the First Photodiode, which acts as in reversed bias condition when light flux falls onto the sensitive surface of the First Photodiode. Correspondingly, diffusion capacity of the First Photodiode, which describes the rearrangement of the minority carriers within the depletion region under the forward bias, is not considered in this equivalent circuit. The equivalent circuit of the First Photodiode in FCIS of FCIS based-LEMCS is shown in Fig.3. Resultantly, the equivalent capacitance is C _eq = Cj+C _s ≡ 200 pF, and at zero bias, ≡ 20 pF at 25 °C. The equivalent resistance of the First Photodiode consists of parallel shunt resistance (R _S h), serial resistance of bulk semiconductor (R _s ), and parallel input resistance of the following current to voltage amplifier (Ri), directly corresponding to the electrometer used in this invention. The equivalent resistance is For the First Photodiode used in the invention, R _S h≡ 10 ΜΩ, R _s ≡ 800 Ω and Ri≡ 0.72 Ω, yields an equivalent resistance R _eq ≡ 800 Ω, corresponding to a time constant of R _e q C _e q ≡ 16xl0" ⁸ s (160 ns) for the First Photodiode at 25 °C. Due to the fact that any additional reversed bias voltage is not applied to the First Photodiode, the photocurrent I _P h(t) doesn't contain dark current and it contains the photocurrent induced by the average power of Pulsed Type Laser Source which has Poisson type noise distribution and Boltzmann Noise current. Even if not applying any reversed bias to the First Photodiode in the invention reduces the higher frequency limit, the noise limit of the First Photodiode of FCIS become better and this approach enables FCIS reaching a threshold level of 1 nA in non-cooling mode, corresponding to 16.5 pj at 1550 nm level for a Duty Cycle of 0.17 at 1 MHz, -3 dB frequency range, in practice.

In this section the pulse and the modulation frequency responses of FCIS based- LEMCS invented: Modulation frequency response of FCIS caused by the RC low pass filter type equivalent circuit consisting from the resistance and capacitance values of the First Photodiode, other effect restricting the pulse and the modulation frequency responses of FCIS is the time constant (τ) of FCIS, based on the diameter of the integrating sphere, coating average reflectance of the inner coating, and light velocity. The time constant (τ) of FCIS is an effective component on determination of average power P _av and resultantly averaged pulse energy by FCIS through the First Photodiode.

By considering the below evaluations concerning with the modulation frequency response of FCIS through the First Photodiode against the rising, the falling edges of the optical light pulses together with pulse width PW, generated by Pulsed Type Laser Source, the pulse response of FCIS should be taken into account, because repetition rate of 1 MHz, corresponding to a period of 1 μ5, should have the rise and the fall times relatively very lower than 1 μ5. For these edges together with relatively short PW can be regarded as δ-delta impulse function for FCIS with an inner diameter of 15 cm which has the First Photodiode and the investigation is made according to the modulation frequency response pertaining to the repetition frequencies up to 1 MHz. As a result, it is obvious that increasing of the modulation frequency gives rise to shortening the rise and the fall time of the pulses as well as PW. In this case, the pulse energy term in Eq.(7) should contain the pulse response term. Therefore Eq.(7) can be rearranged and considered in two parts as in Eq.(9) and as in Eq.(10). First, the pulse response needing to be investigated for measuring P _av in the invention is that of the First Photodiode, behaving as a RC low pass filter against the optical pulses having increasing repetition rates. If the complete pulse response of a RC low pass filter circuit composed of the parallel combination of R _eq and C _eq is calculated, the rise time and the fall time along with PW at the output photocurrent I _av of the First Photodiode also exhibits exponential behavior. In this case, by assuming the laser pulse entering in FCIS, the peak power of which is Po, we can write the pulse energy PEo as Eq.(9) for single laser pulse, containing the pulse response of FCIS and the pulse response of the First Photodiode, and it should be noted that I _P ho should have a rectangular function form. p ₀ = ζΡΊ-ΙζΡΏΒ o < t < PW (W) (9)

^R FCIS

/ t _r + PW+t _f X

Where ζ = 1 1 - e τ I is the pulse response of FCIS against the laser pulse and ζ ^{ρ 1} is the pulse response function of the First Photodiode of FCIS, respectively. A pulse can be divided into three parts. The first part is rising edge t _r , the second part is pulse width PW, and the third part is falling edge, tf. However, in the characterization of the pulse response of the First Photodiode, to think an integrated and complete part of the response of the First Photodiode against the rising edge and the pulse width of the pulse is correct, because in these parts of time of the single pulse, the capacitors of the equivalent circuit are the state of charging and keeping stable. The third part of the single pulse directly corresponds to discharging the capacitors and so third part of the pulse should be represented by a different function. The pulse response function ζ ^{ρ 1} , which is composed of the summation the responses written for three pulse parts, directly relies on the time of charging of capacitors and discharging capacitors through relevant equivalent resistances. This analysis can easily be made by using a continuous convolution of the single pulse with the equivalent circuit of the First Photodiode.

15=*) rect(t) t = t _r + PW 0≤ t≤ PW

Where ζ ^{ρ 1} is the multiplier for I _ph0 , which matches the initial voltage on C _eq just before the discharging of the equivalent capacitor C _eq was started for∞ > t > PW. The pulse energy PE ₀ of a single laser pulse including the pulse responses is, PE ₀ = PW P ₀ = PW-^C ^pdl C ^FCIS (W) (11)

^R FCIS

Where t _r , t _f , and PW are the rise time, the fall time and the pulse width of the pulse of the laser pulse. For the single pulse PW » 160 ns, and t _r < < PW for both pulse response functions; C ^pd ns. The pulse width of 736 ns is

sufficiently larger than 160 ns for this approximation, producing 0.99 I _av .

2 D 1

The parameter ^{T = _} " J^^ * ^s t ^ne time constant of FCIS, p is the average reflectance of the inner coating of FCIS, D is diameter of FCIS, and c is the velocity of light in vacuum. The term corresponds to average number of reflections until a photon is to be absorbed [3 and 4]. It is possible to measure τ of FCIS by measuring the rise times of a very short pulse, which has a pulse width of a few ps, at the entrance port and at the detector port after first reflection. Regarding the time constant τ of FCIS, bearing in mind that quasi-exponential absorption behavior of the inner wall coating of FCIS having highly diffusive reflection is in accordance with the Beer Lambert Law for a photon flux emitted from Pulsed Type Laser Source and assuming that the inner coating of FCIS is nearly uniform and the inner volume of FCIS having a diameter of 15 cm is nearly isotropic, we can say that the pulse response of integrating sphere have an exponential behaviors for rise and fall times of the pulse of the Gaussian Laser Beam due to the time constant (τ) and the dissipation of diffusely reflected irradiance of a single light pulse on the entire inner surface of FCIS reaches to any point within an elapsed time At' inside of FCIS [3 and 4]. According to the above assessments, if PW is larger than τ and for CW laser beam instead of pulse P _av goes to Po. If PW is smaller than τ, corresponding to ultra short pulse condition, there is no sufficient time for the uniform and diffuse reflection of a single pulse inside FCIS and P _av cannot be detected. One of the important points to determine the pulse and the modulation frequency response of the First Photodiode used in the application of measuring the average power of the Pulsed Type Laser Source in the invention is to characterize how many portion of Gaussian Laser Beam entering FCIS is diffusely reflected inside FCIS. For this characterization, the ratio between the diffuse power inside FCIS and the direct power entering in FCIS directly corresponds to pdiff

r'diffuse ⁼ ~p~ ' ^w hi ^cn i ^s t ^ne power efficiency between the diffuse power inside FCIS and the direct power entering in the FCIS, ί_.¾Β = 1/(2πτ) is the cutoff frequency of FCIS. The direct spectral responsivity calibration of FCIS based LEMS against Optical Power Transfer Standard, which will be described in the section "Determination of the spectral responsivity Rpcis of FCIS based-LEMCS", eliminates ¾ _ffuse in Eq.(12) because Rp _CIS (A/W) is obtained from the optical flux diffusely reflected inside FCIS and ^diffuse* ¹¹ ^FCIS * ^{s at tne} denominator in Eq.(12).The time constant of FCIS in the invention is τ≡3 ns, corresponding to f 3j _j B≡53 MHz, for a wall coating having an average value of 0.90. In the pulse response function of FCIS based-LEMCS, the pulse response of FCIS based-LEMCS comprises two parts given in Eq.(12). The first part is related to the geometric characteristics of FCIS of FCIS based-LEMCS together with its inner coating property and the second part is related to the equivalent circuit of the First Photodiode. By comparing Eq.(10) and Eq.(ll), Eq.(12) is written as a complete and final equation.

In Eq.(12), it is seen that this type of pulse response function ζ ^{ρ 1} of the First Photodiode causes the distortion of the ideal pulse shape of photocurrent I _P ho generated by the single laser pulse, depending on time constant of the equivalent circuitl71 of the First Photodiode, R _eq Ceq. This shape distortion, is especially resulted from the relatively larger time constant of the First Photodiode R _eq Ceq =160 ns, rather than time constant of FCIS τ≡ 3 ns. The distortion occurs also in phase of the photocurrent pulse produced by the laser pulse with respect to the laser pulse. These distortions negatively affect to carry out the time/frequency related measurements by means of the First Photodiode. These distortions are characterized in Fig. 2 as PW and DT' for the photocurrent I _P h(t) which is generated by the First Photodiode against Pulse Width and Dead Time of Pulsed/Chopped Gaussian laser beams of Pulsed Type Laser Source and Chopped Type Laser Source. To defeat the problematic condition resulted from the distortion based on unreliable time/frequency related measurements, a second photodiode having a relatively higher low cutoff frequency is placed and reserved in the invention, which is one of the new implementations presented in the invention. The averaged photocurrent measurements and time/frequency related measurements are carried out separately by different photodiodes, called the First Photodiode and called the second in the invention.

The term of Eq.(12) for the single pulse PW » 160 ns, and

PW» t _r , tf, which is the pulse response of the First Photodiode mounted to FCIS in Eq.(12), is an effective parameter for the relatively short pulse widths at the higher modulation frequencies, PW of which approaches 736 ns or shorter. A pulse width PW of 736 ns forms the upper time limit for the First Photodiode of FCIS in the invention together with sufficient and necessary Dead Time DT for heat dissipation, which is detailed in the section of "DESCRIPTION". In case of using any other photodiode having eqCeq lower than 160 ns instead of the First Photodiode, to obtain a new PW narrower than 0.736 μ≤ is obvious. At same time, this is also valid for the term of Eq.(12), ζ = which is the pulse response of FCIS of FCIS based-LEMCS in

Eq.(12). The width of the laser pulses having PW wider than 4.6 τ≡ 14 ns is sufficient to allow peak power Po of 0.99 to dissipate (spread) in the inner surface of FCIS. Due to the fact that both of the First Photodiode and the FCIS behave as a low pass filter, provided that the pulse width PW of Pulsed Type Laser Source is sufficiently wide, the peak pulse energy of the infinite laser pulse train is correctly measured. If the pulse width of Pulsed Type Laser Source is very short, relative to pulse response characteristics of FCIS and the First Photodiode, the rise and the fall times of infinite laser pulses of Pulsed Type Laser Source is retarded by low pass filter characteristics of the First Photodiode and the rise and fall times have slower slopes than original states. As a result this retarded rise and fall times causes to carry out measurement of averaged repetition period T _av (or averaged repetition frequency f _av ) having low precision which corresponds to high measurement uncertainty in time/frequency related measurements by using the output photocurrent I _P h(t) of the First Photodiode. And the pulse width PW and the dead time DT values of infinite laser pulse train of Pulsed Type Laser Source are sensed and converted as PW and DT' as in Fig.3. In order to defeat this problematic condition due to limited pulse response of the First Photodiode, in the invention, the time frequency related measurements are carried out by second photodiode. FCIS based-LEMCS is a preferred embodiment and the variation in numerical values doesn't change the philosophy of the invention.

The two of the most related international patents still in progress to the invention described herein are introduced at the following:

The invention described in US2013250997 (Al) deals with the thermopile type laser energy conversion. The thermopile theory of detecting the laser pulse energy relies on the temperature drop between the hot and cold thermocouple junctions across which the heat, caused by laser energy, flows radially, and the temperature drop results in a voltage output proportional to laser energy applied. This voltage output proportional to laser energy is collected with an integrating circuit receiving the electrical output from the thermopile, such that the energy of at least one pulse of the beam can be determined by integrating over time the electrical output arising from the at least one pulse. The response time of such a thermopile sensor is typically no faster than 1 s for reaching 95% of the final reading and the maximum repetition period to be measured with this system was stated as 10 Hz. However, FCIS based-LEMCS doesn't contain any thermopile type temperature sensor. Instead of using a thermopile, FCIS based-LEMCS is mainly composed of newly configured integrating sphere assembled with the photovoltaic type photodiodes, called the First Photodiode and the Second Photodiode and the averaged pulse energy of the Pulsed Type Laser Source e is determine by measuring by the averaged photocurrent proportional to the peak power of the Pulsed Type Laser Source and by measuring time related measurements of the Pulsed Type Laser Source for a repetition frequency extending to 1 MHz, corresponding to a repetition period of 1 μ5, which is relatively very higher response time with respect to the system described in US2013250997 (Al). FCIS based-LEMCS described herein is a preferred embodiment, the upper cutoff frequencies of the First Photodiode and the Second Photodiode don't disturb the philosophy of the invention described herein and so the photodiodes, the cutoff frequencies of which are higher than lMHz and 6 GHz, really and undoubtedly get better. Additionally, both the First Photodiode and the Second Photodiode specified herein can be exchanged with different types of semiconductor detector depending on the spectral power distribution of the laser to be engaged in the application

Another invention described in JPS63100335(A) deals with securely detecting the energy of a laser beam by providing a laser detector for detecting the energy of a laser beam which is reflected and uniformed by a laser beam scattering device, which is a motorized chopper, and an integrating sphere. The detector mounted to the integrating sphere in JPS63100335(A) senses the uniformly scattered and reflected laser beam portion and the invented systems acts as laser energy presence sensor. Any pulse energy measurement procedure of laser is not seen in JPS63100335(A). However, beyond the detection of presence of laser energy, FCIS based-LEMCS described herein provides both the measurement capability of the averaged pulse energy of the Pulsed Type Laser Source and the calibration of Commercial Laser Energy Meter against FCIS based-LEMCS by using Chopped Type Laser Source, which is a part of FCIS based- LEMCS, and which is traceable to primary level standards.

REFERENCES

[1] Oguz Celikel, Ozcan Bazkir, Mehmet Kucukoglu, and Ferhat Samedov, "Cryogenic radiometer based absolute spectral power responsivity calibration of integrating sphere radiometer to be used in power measurements at optical fiber communication wavelengths", Optical and Quantum Electronics. 37, 529-543, (2005).

[2] Ferhat Sametoglu "New traceability chains in the photometric and radiometric measurements at the National Metrology Institute of Turkey", Optics and Lasers in Engineering 45,36-42, (2007).

[3] Volker Jungnickel, Volker Pohl, Stephan Nonnig, and Clemens von Helmolt "Physical Model of the Wireless Infrared Communication Channel" IEEE Journal on Selected Areas in Communications, vol. 20, no.3, 631-640, (April 2002).

[4] Labsphere Technical Guide: Integrating Sphere Photometry and Radiometry. http: //www.labsphere.com/uploads /technical-guides/a-guide-to-integrating-sphere- radiometry-and-photometry.pdf

[5] Oguz Celikel "Mode Field Diameter and cut-off wavelength measurements of single mode optical fiber standards used in OTDR calibrations" Optical and Quantum Electronics. 37, 587 (2005). [6] David Bergstrom "The Absorption of Laser Light by Rough Metal Surfaces", Doctoral Thesis, Department of Engineering, Physics and Mathematics Mid Sweden University Ostersund, Sweden, February 2008.

SUMMARY

After the completion of the investigation about the pulse responses of FCIS of FCIS based-LEMCS and the First Photodiode mounted to FCIS for a single pulse application in this invention, this section mainly deals with describing the averaged pulse energy including the modulation frequency response function of integrating sphere part of FCIS together with that of the First Photodiode mounted to FCIS so as to reach the exact averaged pulse energy values of Pulsed Type Laser Source and Chopped Type Laser Source, which produces the reference and averaged pulse energy to be used for calibrating Commercial Laser Energy Meter because the invented FCIS based-LEMCS is subjected to infinite laser pulse train, which is composed of an infinite series of single laser pulse in time domain.

In the invention, a-) As a new configuration, FCIS based-LEMCS to be engaged for measuring the averaged pulse energy PE _av of a Pulsed Type Laser Source having Pulsed Gaussian Laser Beams as infinite pulse train in time domain is described. b-) A new apparatus, called FCIS based-LEMCS and the calibration method belonging to the new apparatus along with a newly configured FCIS based-LEMCS equipped with a series of choppers, which is a preferred embodiment, which contains a Chopped Type Laser Source obtained from CW Laser Sources, and which enable us adjusting the Duty Cycles changing from 0.17 to 0.84 at the repetition frequencies varying from 5 Hz to 2 KHz, is described to make the traceable calibrations of Commercial Laser Energy Meters, which operates on the spectral range of 900 nm - 1650 nm over the averaged pulse energy range of 16.5 pj to 100 mj, to primary level standards. With the choice to use an electronic amplitude modulator instead of a group of choppers in the invention, constructed as a preferred embodiment, upper frequency level of 2 kHz, which is available by means of DC motor having a rare earth doped magnet, can be expandable to 1 MHz region, which is the cutoff frequency of the First Photodiode.

In FCIS of FCIS based-LEMCS, two photodiodes are used, labeled as the First Photodiode and the Second Photodiode. The former is engaged in the measurement of average photocurrent I _av , resulted from the average power of the Pulsed Type Laser Source and the latter is used in repetition period T _av (and/or f _av ) measurements of the Pulsed Type Laser Source. For FCIS based-LEMCS, it is seen and proved that the repetition frequency range for an electronic type modulator instead of DC motor driven choppers, which is to be used to construct Chopped Type Laser Source in the traceable calibration of Commercial Laser Energy Meters in the invention, can be extend up to 1 MHz, which is the cutoff frequency limit of the First Photodiode. For the frequencies beyond 1 MHz, the pulse response and modulation response functions mentioned in the section of "BACKGROUND" should be taken into account. As seen in the time constants of FCIS and the First Photodiode mounted to FCIS, the modulation frequency range of integrating sphere of FCIS is wider than that of the First Photodiode and so bearing in mind that for the Pulsed Type Laser Source, T _av (=l/f _av ) is equal to the averaged values of (PW+DT+t _r +tf), it is enough to write the average photocurrent I _av as a function of the modulation frequency of the Pulsed Type Laser Source so as to define the modulation frequency dependency of the resultant averaged pulse energy value PE _av in unit of J, caused by the dependency of the First

Photodiode only. The cutoff frequency of FCIS is ⁼ V(2 ₇ rt) ^≡ ^ MHz. In this case, the modulation frequency response function of FCIS is assumed as 1 for the frequency band of 0 - 1 MHz in which the First Photodiode operates. By considering the Fourier Series expansion of an infinite and periodic pulse train, the averaged repetition frequency of which is f _av = 1 MHz, the highest amplitude of the first odd frequency component of Fourier series expansion belonging to the infinite and periodic pulse train is at f = 1 MHz. The following frequencies together with a DC component are 2 MHz, 3 MHz, ,n f, with the decreasing amplitude. In this case, the other following frequency contents higher than 1 MHz constituting the infinite and periodic pulse train are attenuated with a relatively higher slope (20 dB/decade) by the First Photodiode behaving as a RC low pass filter. The cutoff frequency of which is ~1 MHz Hz). With this brief evaluation, instead of summing all of the frequency responses of the First Photodiode against the infinite and periodic pulse train, the first Fourier term, which has sinusoidal behavior, is considered and the modulation frequency response function of the First Photodiode is calculated according to sinus function, the linear frequency of which corresponds to the averaged repetition frequency f _av (Hz), the first odd frequency component of Fourier series expansion of infinite and periodic pulse train. This approach gives very good explanation for the modulation frequency dependence of FCIS. As a result, the final form of PE _av in Eq. (13) is calculated by multiplying I _P h(t) in Eq.(12) with the modulation frequency transfer function ξ ^ρ (ΐ _Άν ) of the equivalent circuit of the First Photodiode, behaving as a RC low pass filter in Fig.3, for the sufficiently wide pulse widths. For the infinite laser pulse train generated by Pulsed Type Laser Source, the averaged pulse energy is given in Eq.(13);

PEav (fav) = ^Ta !y ^ffav) = 0) (13)

^{1 K} FCIS ^r av ^{N k} FCIS

Eq.(14) characterizes Eq.(13) as a function of the repetition frequency f _av (Hz), corresponding to the modulation frequency response functions of FCIS based-LEMCS and the First Photodiode, instead of the pulse response functions terms in Eq.(9) and Eq.(10).

Iav(fav) = <Iph M > ξ ^{Ρ£} 1} (ί ₃ ν)ξ ^Ρα5 (ί ₃ ν)≡ ⁰ < ^f - ^{≤ 1 MHz} C ¹⁴ )

Where the phase terms of Eq.(15), based on frequency terms, is discarded. The term pels · caused by time constant of FCIS τ (s) in Eq.(10), can be neglected and dropped for

'-3dB the repetition frequencies up to the upper frequency limit of 1 MHz of the First Photodiode valid in this invention. f-¾dBi ^s the high frequency cutoff limit of the First Photodiode, behaving as a RC low pass filter in Fig.3, which can be calculated from (Req.Ceq) as ~1 MHz Hz) theoretically. The frequency range from 0 Hz up to 1 MHz, which is also obtained by the theoretical calculations, is verified by the measurements carried out by FCIS assembled with the electrometer. The role of the modulation response function of the First Photodiode ξ ^{ρ _1} (f _av ) is presented in Eq.(14). The resultant averaged peak pulse energy PE _av of a Pulsed Type Laser Source as a function of the averaged repetition frequency is given in Eq.(16), by considering the first odd term of Fourier Expansion series of the pulse train having a varying PW. Eq.(16) is a well suited model function for FCIS of FCIS based-LEMCS in the invention, characterizing both of the modulation frequency response and the pulse response of the FCIS system. Considering the MHz, the modulation frequency response function of the whole of FCIS composed of an integrating sphere and the First Photodiode consists of ξ ^{ρ _1} (f _av ) only for the repetition frequency range extending from 0 to 1 MHz, by multiplying ξ ^{ρ _1} (f _av ) with ξ ^ρα5 (ί _3ν )≡η _£ΐ . _ίίιΐί . _β . However, the robustness of the method presented in the invention give us an advantage to eliminate ¹ Averaged pulse energy of the Pulsed Type Laser Source is as follows by considering the modulation frequency response function of FCIS based-LEMCS, which is final equation by which the averaged pulse energy is calculated in the invention.

Where

frequency range of FCIS based-LEMCS which is up to 1 MHz in measuring the averaged pulse energy of Pulsed Type Laser Source and is 2 kHz in calibration of Commercial

Laser Energy Meter against FCIS based-LEMCS invented, the term * ^{s n} °t

included in Eq.(16). This is also valid for the range of the repetition frequency of 1 MHz. λ ₌ I ^res P (A)

FCIS , which is determined from the calibration of FCIS against Optical Power

Transfer Standard. The direct spectral responsivity calibration of FCIS based LEMS against Optical Power Transfer Standard, which will be described in the section "Determination of the spectral responsivity Rpcis of FCIS based-LEMCS", eliminates ^diffuse ^m Eq.(16) because Rpcis (A/W) is obtained from the optical flux diffusely reflected inside FCIS and η ,. _ff in Rpcis * ^{s at} the denominator in Eq.(16). If the background current Ibc, which fluctuates around zero line, takes place in the First Photodiode, this background current Ibc is subtracted from I _av to obtain correct averaged photocurrent caused by Gaussian laser pulses produced by Pulsed Type Laser Source. Duty Cycle = f _av .PW _a¥ = (N.PW _av )/T _av N is 1 for infinite pulse traingenerated by Pulsed Type Laser Source in this invention. Due to the fact that PE _av (f _av ) and the averaged repetition period T _av (s) are measured within a time interval determined by the average times of Electrometer and Time Interval Counter adjusted by operator during the pulse energy measurements, these are directly averaged values.

NOTE: The time/frequency related parameters, which are f (Hz), T(s), PW (s), DT (s) and stated in the text are not time averaged values. However, f _av (Hz), T _av (s), PW _av (s), and DT _av (s) parameters are the time averaged values obtained from the measurements of the time/frequency related parameters, which are f (Hz), T(s), PW (s), DT (s), by means of Time Interval Counter of FCIS based-LEMCS within a time interval adjusted by operator.

Time/frequency related measurements (T _av and f _av ) in Eq.(16), which are traceable to ¹³³ Cs (or ⁸⁷ Rb) frequency standard through a commercial Time Interval Counter, are directly performed by fully eliminating the effect of relatively lower cutoff frequency of the First Photodiode and the effects of the time constant of FCIS on dissipation rate of the irradiation of P(t) diffusely reflected after collision of a Pulsed Gaussian Laser Beams of Pulsed Type Laser Source on the diffusive inner surface of FCIS with a novel placement of a fast response photodiode in the conventional integrating sphere, called as the Second Photodiode. This elimination is achieved with help of a small hemisphere placed inside FCIS assembled with the first MM optical fiber patch cord having a Zr ferrule, the core diameter of which is 62.5 μηι, and this is applicable for the integrating spheres to be used for higher peak laser energy the inner diameter of which is larger than 15 cm. The entrance port of FCIS and the center position of steel hemisphere are coincided on the same optical axis and the optical pulses strike on Zr ferrule settled on the center of the Small Steel Hemisphere first. The time/frequency related measurements are directly carried out for the pulse strikes of Pulsed Type Laser Source and the pulse strikes of Chopped Type Laser Sources by the combination of the Second Photodiode, Fast Current to Voltage Converter, and Time Interval Counter. With this configuration, all of the time measurements are performed as free of the time constant (τ = 3 ns) of integrating sphere of FCIS and free of time constant of R _eq Ceq≡16xl0 ^"8 s (160 ns) of the First Photodiode used to measure average power I _av . The measurements of I _av in Eq.(16) are carried out by an electrometer, the traceability of which comes from primary resistance standard, Quantum Hall System, and comes from primary direct voltage standard, DC Josephson System. The traceability of optical power scale of FCIS, which corresponds to the spectral responsivity of FCIS, Rpcis _> ^m Eq.(16) through the First Photodiode is provided by an Optical Power Transfer Standard, InGaAs based spectralon sphere radiometer, as a preferred embodiment in the invention. BRIEF DESCRIPTION OF DRAWINGS

Figure 1. The invented Fiber Coupled Integrating Sphere Based-Laser Energy Meter and Calibration System (FCIS based-LEMCS) without Chopped Type Laser Source in the measurement of the averaged peak pulse energy of a Pulsed Type Laser Source.

Figure 2. The setup for calibration of Commercial Laser Energy Meter against FCIS of FCIS based-LEMCS by FCIS based-LEMCS. This drawing shows the whole of FCIS based- LEMCS with the dashed lines.

Figure 3. Pulse characteristics of Pulsed Type Laser Source / Chopped Type Laser Source the average pulse energy of which is to be measured by FCIS based-LEMCS in the invention and the photocurrent proportional to the average optical power P _av , generated by the First Photodiode.

Figure 4. The details and the components of FCIS of FCIS based-LEMCS and reflection properties together with the placements of Pulsed Type Laser Source and Chopped Type Laser Source.

Figure 5. Details of stainless steel body of Small Steel Hemisphere for the energy transfer and laser pulse parameter calculations in the determination of the pulse energy damage limit.

Figure 6a. Choppers mounted on the DC motor, which has a rare earth doped magnet, 0.83, 0.75, 0.67, and 0.58 at constant repetition frequency of f ^ ^clem . These choppers in the invention are used to construct Chopped Type Laser Source from CW Laser Source(s), which is to be engaged as a reference and averaged pulse energy in traceable calibration of Commercial Laser Energy Meter.

Figure 6b. Choppers mounted on the DC Motor, which has a rare earth doped magnet, to generate Duty Cycles of 0.50, 0.42, 0.33, 0.25 and 0.17 at constant repetition frequency of fgy ^{f clem} . These choppers in the invention are used to construct Chopped Type Laser Source from CW Laser Source(s), which is to be engaged as a reference and averaged pulse energy in traceable calibration of Commercial Laser Energy Meter.

Figure 7. Traceability chain of FCIS based-LEMCS, which is to be used in both measuring the averaged pulse energy PE _av of Pulsed Type Laser Source and calibrating Commercial Laser Energy Meters by using the reference and averaged pulse energy of Chopped Type Laser Source of FCIS based-LEMCS.

Figure 8. The setup for the determination of spectral responsivity Rpcis (A/W) of FCIS of FCIS based-LEMCS traceable to Cryogenic Radiometer, primary level optical power standard (W).

Figure 9a. The uncertainty budget belonging to FCIS based-LEMCS for an averaged pulse energy PE _av of 40 μ] as a rated value. Figure 9b. The uncertainty budget belonging to FCIS based-LEMCS for an averaged pulse energy PE _av of 100 mj as a rated value.

DESCRIPTION

The details of FCIS based-LEMCSlll, which is constructed as a preferred embodiment, which is used to measure the averaged pulse energy of a Pulsed Type Laser Source500 and to calibrate a Commercial Laser Energy Meter999 with the reference and averaged pulse energy generated by Chopped Type Laser Source600 in the structure of FCIS based-LEMCSlll, which is traceable to primary level standards, are presented herein.

FCIS based-LEMCSlll which is the subject of the invention is completely shown in Fig.2. The structural body of FCIS based-LEMCSlll consists of the configuration of FCISIOO detailed in Fig.4, Small Steel Hemisphere assembled with Zr ferrulel40 of HMS connectorl32 of a First MM Optical Fiber Patch Cordl50 detailed in Fig.5, nine separate choppers901-909 detailed in Fig.6a and Fig.6b, which are mountable to DC Motor599, an Electrometerll9, a Time Interval Counterl35, an Oscilloscopel30, a Mechanical Attenuatorl70, an Alignment Combinationl62 and a second MM optical fiber path cordl60 shown in Fig.l and Fig.2. Even though the Electrometerll9, the Time Interval Counterl35, the Oscilloscopel30, the Mechanical Attenuatorl70, the Alignment Combinationl62, the first MM optical fiber path cordl50 and the second MM optical fiber path cordl60, which are general purpose measurement instruments and apparatus, are excluded from the invention individually, they are included in the invention for both the measurement procedure of the averaged pulse energies PE _av 840 of Pulsed Type Laser Source500, and the calibration of Commercial Laser Energy Meters999 to be performed by using the reference and averaged pulse energies PEa ^clem 845 of Chopped Type Laser Source600 of FCIS based-LEMCSlll, all of which are traceable to primary level standards demonstrated in Fig.7.

In addition to traceable measurements of the averaged pulse energy PE _av 840 of Pulsed Type Laser Source500 by FCIS based-LEMCSlll, the traceable calibration of Commercial Laser Energy Meters999, which measure the averaged pulse energy, are carried out by the reference and averaged pulse energies generated by means of Chopped Type Laser Source600, which is a part of FCIS based-LEMCSlll. The method of traceable calibration of Commercial Laser Energy Meters999 via FCIS based- LEMCSlll is included in the invention. The invention is summarized at the following three items;

1-) The averaged pulse energy measurement section of FCIS based-LEMCSlll designed for measuring the averaged pulse energy PE _av 840 of Pulsed Type Laser Source500 shown in Fig.l, consists of an Al-integrating sphere having a diameter of 150 mm, called as FCISIOO in the invention, a Small Steel HemispherellO assembled with Zr ferrulel40 of HMS connectorl32 of a First MM Optical Fiber Patch Cordl50, which is mounted inside FCISIOO, the details of which are given in Fig.4, the Electrometerll9 able to measure the photocurrent I _av 300 generated by the First Photodiodel20 mounted on Port_2102 of FCISIOO of FCIS based-LEMCSlll, the Second Photodiodel29 mounted on Port_3103 of FCISIOO of FCIS based-LEMCSlll through the First MM Optical Fiber Patch Cordl50 having Zr ferrulel40, which is to be used in time and frequency measurements together with Time Interval Counterl35 and the Oscilloscopel30 in Fig.l.

2- ) The composition of FCIS based-LEMCSlll, which is a series of separate choppers901-909 to construct a Chopped Type Laser Source600 generating the reference and averaged pulse energy for the calibration of Commercial Laser Energy Meter999 together with all of the equipments, all of the parts, all of the configurations stated in item "1-)" just above. The whole of FCIS based-LEMCS is shown in Fig.2. The combination of a DC motor599 with a series of separate choppers of FCIS based-LEMCSlll, each of which has individual Duty Cycle shown in Fig. 6a and Fig. 6b, is used in establish Chopped Type Laser Source600 generating an infinite pulse train from CW Laser Sources800 in Fig.2 and Fig.3 in order to calibrate Commercial Laser Energy Meters against FCIS based-LEMCSlll, traceable to primary level standards. In brief, Chopped Type Laser Source600 of FCIS based-LEMCSlll generates the reference and averaged pulse energy PE^ ^cIem 845 to calibrate Commercial Laser Energy Meters 999.

3- )The measurement method of the averaged pulse energy PE _av 840 of the Pulsed Type Laser Source500 with FCIS based-LEMCSlll, and the calibration method of a Commercial Laser Energy Meter999 against Chopped Type Laser Source600 of FCIS based-LEMCSlll, both of which are traceable to primary level standards. Due to the fact that the FCIS based-LEMCSlll is a preferred embodiment the variation in the properties and the number of the choppers generating different Duty Cycles doesn't disturb the philosophy of the invention. Additionally, FCIS based-LEMCSlll described herein is a preferred embodiment, the upper cutoff frequencies of the First Photodiodel20 and the Second Photodiodel29 don't disturb the philosophy of the invention described herein and so the photodiodes, the cutoff frequencies of which are higher than lMHz and 6 GHz, really and undoubtedly get better. Additionally, both the First Photodiode and the Second Photodiode specified herein can be exchanged with different types of semiconductor detector depending on the spectral power distribution of the laser to be engaged in the application.

1. Details of FCIS

The FCISIOO of FCIS based-LEMCSlll has three ports: These are Laser Entrance PortlOl (Port_l), Average Optical Power Measurement Portl02 (Port_2), and Time/Frequency Related Measurement Portl03 (Port_3). These ports dwell on the same equator line of the FCIS shown as in Fig.4.

Port_l;

The diameter of Port_1101 is 8 mm. The diameter of 8 mm of Port_l enables Pulsed Gaussian Laser Beam501 of Pulsed Type Laser Source500, Chopped Gaussian Laser Beam601 of Chopped Type Laser Source600, and CW Laser Source800, sequentially shown in Fig.l, Fig.2, and Fig.8, to enter in FCISlOO of FCIS based-LEMCSlll without any contact by considering the beam waits and total beam diameters in the measurement of the averaged pulse energy PE _av 840 of Pulsed Type Laser Source500of Fig.l, in the measurement of the reference and averaged pulse energy PE^ ^cIem 845 of Chopped Type Laser Source600 of Fig.2 and in the determination of spectral responsivity Rpcis320 of FCISlOO of FCIS based-LEMCSlll with the CW Gaussian Laser Beam799 of CW Laser Source800 of Fig.8. The distance and beam divergence correlations among the point z=0 and Port_1101 and the center of the Small Steel HemispherellO in Fig.l, Fig.2, and Fig.8 should provide the contactless passing of the Pulsed Gaussian Laser Beam501, Chopped Gaussian Laser Beam601, and CW Gaussian Laser Beam799.

The following calculations related to beam waist and beam divergences to be carried out for CW Gaussian Laser Beam799 of CW Laser Source800, which are used to construct Chopped Type Laser Source600 of FCIS based-LEMCSlll in Fig.2 by means of a series of choppers901-909 shown in Fig.6a, and Fig.6b, which generates the reference and averaged pulse energy PE^ ^cIem 845 to be used in the calibration of Commercial Laser Energy Meter999 against FCIS based-LEMCSlll are also taken into account for the measurement of the averaged pulse energy PE _av 840 of Pulsed Type Laser Source500.

The four distributed feedback (DFB) laser diodes, each of which is called as CW Laser Source800 in FCIS based-LEMCSlll constructed as a preferred embodiment in the invention, each of which individually radiates at 980.0 nm, 1064.0 nm, 1309.0 nm, and 1549.0 nm, and all the four of which have individual Single Mode (SM) Optical Fiber Patch Cords876 assembled with the individual collimators, are used in the determination the spectral responsivity R^ _CIS 320 of FCISlOO of FCIS based-LEMCSlll in Fig.8 and in the traceable calibration of Commercial Laser Energy Meters999 in Fig.2 obtained by means of the nine different choppers901-909 shown in Fig.6a and Fig.6b.

Single mode propagation inside the optical fiber patch cords of the four laser diodes means the field distribution of quasi transverse electric mode (LPoi) HEn, no higher order modes. The width (beam waist w(z), 1/e ² (13.53%) points of the irradiance level) change of the irradiance distribution at the output of the single mode optical fiber, corresponding to Gaussian beam profile, is the function of the numerical aperture of the relevant single mode optical fiber of the patch cord [5] and these beam waists of the irradiance distributions diverge, depending on the distance z from the end of fiber, the wavelength and the spectral band width which is relatively narrow for DFB lasers. Beam divergence of a Gaussian beam is described as Θ = Arctan (w(z)/z) in (rad) or (deg), where w(z) is the beam waist at any distance z (mm) on the propagation way of the laser beam emerging from the output of the Single Mode (SM) Optical Fiber Patch Cord with Collimator876 of each CW Laser Sources800. The total beam divergence is equal to 2Θ.

w(z=0)=2.0 mm, beam divergence 1.20 mrad at 980.0 nm,

w(z=0)=2.4 mm, beam divergence 1.50 mrad at 1064.0 nm,

w(z=0)=2.7 mm, beam divergence 1.50 mrad at 1309.0 nm,

w(z=0)=2.8 mm, beam divergence 1.52 mrad at 1549.0 nm.

For a distance of 300 mm between the output of the Single Mode (SM) Optical Fiber Patch Cord with Collimator876 and the center of the Small Steel HemispherellO, the beam divergence calculations are performed. The distance of 300 mm means a distance extending from z=0 to the center of Small Steel HemispherellO where a Small Pin Holel09 with a diameter of 0.1 mm is drilled and Zr ferrulel40 of HMS Connectorl32 of the First MM Optical Fiber Patch Cordl50 is located in the center position of the Small Steel HemispherellO and 0.2 mm back from the center surface of Small Steel HemispherellO at rest position shown in Fig.4 and Fig.5. In this case the total beam waists with the relevant divergences for the distance of 300 mm at the center of Small Steel HemispherellO are calculated as follows:

The total beam divergence 2Θ = 0.72 mm and the total beam waist is 2.72 mm for 980.0 nm CW Laser Source800, The total beam divergence 2Θ = 0.90 mm and the total beam waist is 3.30 mm for 1064.0 nm CW Laser Source800,

The total beam divergence 2Θ = 0.90 mm and the total beam waist is 3.60 mm for 1309.0 nm CW Laser Source800,

The total beam divergence 2Θ = 0.92 mm and the total beam waist is 3.72 mm for 1549.0 nm CW Laser Source800.

Port_2;

Port_2102 is an aperture, the diameter of which is 2 mm, as shown in Fig.4. The First Photodiodel20 is located in Port_2102. The average photocurrent measurements I _av 300, and I™ ^f - ^clem 842, which are related to the average optical power P _av 301 of either Pulse Type Laser Source500 or Chopped Type Laser Source600 as in Fig.3 respectively, are carried out by means of the First Photodiodel20 connected to the Electrometerll9 able to measure the levels of sub-femto amperes in high accuracy mode. In addition to the averaged photocurrents labeled as I _av 300, and I _ay ^{f cIem} 842, the First Photodiodel20 of FCISIOO of FCIS based-LEMCSlll generates the photocurrent I ^res P200 during the traceable spectral responsivity calibration Rp _CIS 320 of FCISIOO of FCIS based- LEMCSlll, shown in Fig.8. This photocurrent I ^res P200o f the First Photodiode is used for deriving the spectral responsivity Rp _CIS 320 of FCISIOO by dividing I ^res P200 with pcw_res _P ( )201, which is obtained from Optical Power Transfer Standard809 directly. The First Photodiodel20 mounted to Port_2102 generates the photocurrents proportional to the irradiance levels of Pulsed Gaussian Laser Beams, Chopped Gaussian Laser Beams, and CW Gaussian Laser Beams entering from Port_l without saturation up to an average optical power of -158 W by considering its saturation level of 7 mW. The photocurrent produced by the First Photodiodel20 is converted into voltage and averaged by the Electrometerll9. The First Photodiodel20 at Port_2102 can operate up to a repetition rate of 1 MHz, which is the cutoff limit of the First Photodiodel20.The details about the pulse and the modulation frequency response characteristics of the First Photodiodel20 are introduced in the Sections "Background" and "Summary". In the invented FCIS based-LEMCS, the First Photodiodel20 located in Port_2102 is used for only measuring the average photocurrent I _av 300, and I _ay ^{f cIem} 842 resulted from the average optical powers P _av 301 of Pulsed Type Laser Source500 / Chopped Type Laser Source600 in Eq.(16) only. In measuring the time/frequency related parameters of Pulsed Type Laser Source500 and Chopped Laser Source600, the First Photodiodel20 at Port_2102 has not any responsibility, the main and the single mission of the First Photodiodel20 of FCISIOO of FCIS based-LEMCSlll is only to measure the average photocurrents I _av 300, and I^ ^cIem 842 proportional to the averaged optical power levels P _av 301 of Pulsed Type Laser Source / Chopped Type Laser Source as shown in Fig.3. Furthermore, according to Eq.(16), the spectral responsivity R _FCIS 320 of FCIS of FCIS based-LEMCS needed to calculate the averaged pulse energy PE _av 840 of Pulsed Type Laser Source500 and the reference and averaged pulse energy PE _ay ^{f cIem} 845 of Chopped Type Laser Source600, corresponding to spectral responsivity of the First Photodiodel20 mounted to Port_2102, is performed by its direct comparison to Optical Power Transfer Standard, calibrated against CR803 [1] and, the First Photodiodel20 produces an averaged photocurrent I ^res P200 in the determination process of the spectral responsivity Rp _CIS 320.

All the average photocurrents I _av 300, I _a v ^{f clem} 842 and I ^res P200 generated produced by the First Photodiodel20 mounted to Port_2102 are collected and averaged by the Electrometerll9, which is traceable to Quantum Hall Resistance Standard and DC Josephson Voltage Standard through Reference Resistance Bridge as shown in Fig.7. The traceability chain for I _av 300, I _a v ^{f clem} 842 and R _FCIS (A/W)320 is also demonstrated in Fig.7. Port_3;

The aims of the use of the Second Photodiodel29 linked to Port_3103 of FCISlOO of FCIS based-LEMCSlll through Mechanical Attenuator and the first MM optical fiber patch cord as in Fig.l and Fig.2 are i-) to perform the time/frequency related measurements of Pulsed Type Laser Source500 / Chopped Type Laser Source600 without the effect of time constant of FCISlOO and without the effect of the relatively lower cutoff frequency of the First Photodiodel20 and ii-) to coincide the Optical Axis398 of FCIS based-LEMCSlll with the those of the Pulsed Type Laser Source500, Chopped Type Laser Source600, and CW Laser Source800 highly repetitively so as to obtain high measurement reproducibility. In addition to time/frequency related measurements of Pulsed Type Laser Source500, Chopped Type Laser Source600 during PE _av 840 and PE^ ^cIem 845 measurements, the Second Photodiodel29 is also used for highly repetitively coinciding the Optical Axis398 of FCIS based-LEMCSlll with the Optical Axes398 of the Pulsed Type Laser Source500, Chopped Type Laser Source600, and CW Laser Source800 entering from Port_l inside FCIS in Fig.l, Fig.2, and Fig.8 during the measurements of the averaged pulse energy PE _av 840 of Pulsed Type Laser Source500, the determination of the averaged and reference pulse energy PE^ ^cIem 845 of Chopped Type Laser Source for the calibration of Commercial Laser Energy Meters999, and the determination of R^ _CIS (A/W)320 of FCISlOO of FCIS based- LEMCS111 against Optical Power Transfer Standard809.

The FC/PC connector side of the First MM Optical Fiber Patch Cordl50 is joined to input of Mechanical Attenuatorl80 and then the output of Mechanical Attenuatorl80 is combined to the Second Photodiodel29 through the First MM Optical Fiber Patch Cordl60. The photocurrent generated by the Second Photodiodel29 is transformed into voltage by Fast Response Current to Voltage Converterl27. Zr ferrulel40 of HMS connectorl32of the First MM Optical Fiber Patch Cordl50 is mounted inner center surface of Small Steel HemispherellO, which directly sees Port_1101, and which is settled on the equator line inside FCISlOO of FCIS based-LEMCSlll with an angle, i.e. 25° in the invention, which is shown in Fig.4. With this inclination of Small Steel HemispherellO inside FCISlOO, the First Photodiodel20 used in measuring I _av 840, Ia ^clem 845, and I ^res P200 is protected from first reflections of Pulsed Gaussian Laser Beam501 of Pulsed Type Laser Source500, and Chopped Gaussian Laser Beam601 of Chopped Type Laser Source600 entering in Port_1101. The same approach is also valid for CW Gaussian Laser Beam of CW Laser Sources used in the determination of spectral responsivity R^ _CIS 320 of FCISlOO of FCIS based-LEMCSlll against Optical Power Transfer Standard809, and the sufficiently diffusely reflected beamsl48 depicted as in Fig.4 fall on the active area of the First Photodiodel20 mounted to the Port_2102 having a diameter of 2 mm. The first reflectionl49 takes place towards the wall opposite the First Photodiodel20 and the wall of FCISlOO of FCIS based-LEMCSlll, coated with BaSO ₄ 105, reflects the beam, which is reflected first from the center of the polished/mirrored inner surface of Small Steel HemispherellO, interior surface of FCISIOO of FCIS based-LEMCSllldiffusely. Additionally, whenever Pulsed Gaussian Laser Beams501 of Pulsed Type laser Source500 or Chopped Gaussian Laser Beams601 of Chopped Type Laser Source600 or CW Gaussian Laser Beam799 of CW Laser Source800 entering in FCISIOO through Port_1101 collides on the center of Small Steel HemispherellO inclined, i.e. 25° in the invention, it is specularly reflected, called as a first reflectionl49 in Fig.4, to the wall opposite the First Photodiodel20 settling on the same equatorial line. The Pulsed Gaussian Laser Beams501 or Chopped Gaussian Laser Beams601 or CW Gaussian Laser Beam799 colliding on the center of Small Steel HemispherellO begins to distort and their beam waists start to expand after colliding the center of Small Steel HemispherellO due to the inner curvature of Small Steel HemispherellO and the presence of Small Pin Holel09 at the center of Small Steel HemispherellO. The distortion and the expansion of the first reflection beaml49 forms relatively very larger area on the wall coated with BaSO ₄ 105. This type positioning and use of Small Steel HemispherellO inside FCISIOO is very practical for not damaging BaS0 ₄ coated walll05 of FCISIOO and moreover, a sufficient diffuse reflection interior FCISIOO in the invention occurs, increasing the measurement reproducibility in the invention.

Port_3103 is so drilled with an angle that Zr ferrulel40 of HMS connector 132 of the First MM Optical Fiber Patch Cordl50, the length of which is 10 mm, and the outer diameter of which is 2.5 mm, extends to the position 0.2 mm back from the inner surface of Small Steel HemispherellO as in Fig.4 in detail. The First MM Optical Fiber Patch Cordl50 has a Si0 ₂ core, the diameter of which is 62.5 μηι. The crest of Pulsed Gaussian Laser Beams501 of Pulsed Type laser Source500 or the crest of Chopped Gaussian Laser Beams601 of Chopped Type Laser Source600 or the crest of CW Gaussian Laser Beam799 of CW Laser Source800 entering in FCISIOO through Port_1101 is continuously fallen onto the tip of Zr ferrulel40 of HMS connector 132 of the First MM Optical Fiber Patch Cordl50 shown as in Fig.l, Fig.2, and Fig.8 by means of Alignment Combinationl62. Then the Optical Axis398 of FCISIOO and the optical axes of Pulsed Type Laser Source500, Chopped Type Laser Source600, and CW Laser Source800 shown in Fig.l, Fig2, and Fig.8 are coincided by means of Alignment Combinationl62 by on line tracking and maximizing the voltage amplitude at the output of Fast Response Current to Voltage Converterl27 joined to the Second Photodiodel29 on the screen of the Oscilloscopel30. The relative maximum signal amplitude means that the crest of Pulsed Gaussian Laser Beams501 of Pulsed Type laser Source500 or the crest of Chopped Gaussian Laser Beams601 of Chopped Type Laser Source600 or the crest of CW Gaussian Laser Beam799 of CW Laser Source800 directly collides/falls on Zr ferrulel40 placed on the center of Small Steel HemispherellO. This process and the configurations in the invention considerably increase the measurement reproducibility and repeatability. In order to coincide the optical axes of Pulsed Type Laser Source500, Chopped Type Laser Source600, and CW Laser Source800 entering from Port_1101 with the Optical Axis398 settling on the core of Zr ferrulel40 of the First MM Optical Fiber Patch Cordl50 on Port_3103 during the measurements of I _av 300, I™ ^f - ^clem 842, and I ^res P200 is difficult. In order to overcome the difficulty, in the invention, a Small Steel HemispherellO assembled with the combination of the First MM Optical Fiber Patch Cordl50, Mechanical Attenuatorl70, the First MM Optical Fiber Patch Cordl29, and Fast Response Current to Voltage Converterl27 is designed and is mounted inside a conventional integrating sphere which is equipped with the Small Steel HemispherellO assembled with the Zr ferrulel40 of the First MM Optical Fiber Patch Cordl50 illustrated as in Fig.4 and Fig. 5, called Fiber Coupled Integrating SpherelOO (FCIS) in the invention. The Small Steel HemispherellO having an enclosed circular area of Ash=133 mm ² 520 in Fig.4 behaves as a target having a wide circular target area520 of 133 mm ² . Even though inner surface of the Small Steel HemispherellO is chemically and mechanically polished/ mirrored, some portion of the intensive Pulsed Gaussian Laser Beams501 of Pulsed Type laser Source500, Chopped Gaussian Laser Beams601 of Chopped Type Laser Source600, and CW Gaussian Laser Beam799 of CW Laser Source800 colliding inner surface of the Small Steel HemispherellO is launched into the First MM Optical Fiber Patch Cordl50 through its Zr ferrulel40, thanks to a relatively high numerical aperture of optical fiber of the First MM Optical Fiber Patch Cordl50, the remaining diffuse reflectance characteristic and the inner surface curvature of Small Steel HemispherellO, all of which provide a structural advantage for launching of some portion of Pulsed Gaussian Laser Beams501, Chopped Gaussian Laser Beams601, and CW Gaussian Laser Beam799 into the core of Zr ferrule of the first MM optical fiber patch cord. If the intensity of the launched portion of Pulsed Gaussian Laser Beams501 or Chopped Gaussian Laser Beams601 or CW Gaussian Laser Beam799, which is detected by the Second Photodiodel29, is insufficient, the coinciding process is performed by means of Alignment Combinationl62 between the optical axis of Pulsed Type Laser Source500, Chopped Type Laser Source600, and CW Laser Source800 and the Optical Axis398 extending the center of the inner surface of the Small Steel Hemisphere on Port_3103. By this alignment process, the crests of Pulsed Gaussian Laser Beams501, Chopped Gaussian Laser Beams601, and CW Gaussian Laser Beam799 entering from Port_l through the Small Pin Holel09 of 0.1 mm diameter at the center of the Small Steel Hemisphere on Port_3 are coincided on the same optical axis398 and the maximizing process continues until the maximum intensity to be detected by the Second Photodiodel29 is available and is seen on the Oscilloscopel30 screen. As soon as the maximum intensity is obtained, and it is decided that the crests of Pulsed Gaussian Laser Beams501, Chopped Gaussian Laser Beams601, and CW Gaussian Laser Beam799 entering from Port_1101 directly collides to the center of the inner surface of the Small Steel HemispherellO on which a Small Pin Holel09 of 0.1 mm diameter is drilled. In this case, when I _av 300, Iav ^{f clem} 842, and I ^res P200 measurements are performed by the combination of the First Photodiodel20 with the Electrometerll9, the time/frequency related measurements of Pulsed Type Laser Source500, and Chopped Type Laser Source600 are carried out by the combination of the Second Photodiodel29, Fast Response Current to Voltage Converterl27, and Time Interval Counterl35 of FCIS based-LEMCSlll. With this type of the configuration of the first MM fiber patch cordl50 and the second MM fiber patch cordl60 assembled with Small Steel Hemisphere 110 through Mechanical Attenuator 170, the measurement reproducibility of photocurrent parameters I _av 300, ^clem 842, and I ^res P200, which are necessary for calculations of PE _av 840, PEa ^clem 845, and R^ _CIS 320, is relatively enhanced for any relevant Gaussian type laser source, depending on the application in FCIS based-LEMCS such as, Pulsed Gaussian Laser Beams501 of Pulsed Type laser Source500, Chopped Gaussian Laser Beams601 of Chopped Type Laser Source600, and CW Gaussian Laser Beam799 of CW Laser Source800, because the same Optical Axis398 is achieved by maximizing the photocurrent of the Second Photodiodel29 on the screen of the 0scilloscopel30. The maximum photocurrent from the Second Photodiodel29 is obtained by adjusting Alignment Combinationl62 in Fig.l, Fig.2, and Fig.8 as soon as the peak irradiance position (crest) of the Pulsed Gaussian Laser Beams501of Pulsed Type Laser Source500, the Chopped Gaussian Laser Beam601 of Chopped Type Laser Source600, and the CW Gaussian Laser Beam799 of CW Laser Source800 entering from Port_1101 in FCISIOO is matched with 62.5 μηι core of Zr ferrulel40 of the First MM Optical Fiber Patch Cordl50 extending to the inner surface of Small Steel HemispherellO. The tip of Zr ferrulel40 of the First MM Optical Fiber Patch Cordl50 is located back from the inner surface of the Small Steel HemispherellO as 0.2 mm and that is, Zr ferrule 140 of the First MM Optical Fiber Patch Cordl50 is rest backward the center of the Small Steel HemispherellO. In order to launch the Gaussian Laser Beams501, 601, 799 into the First MM Optical Fiber Patch Cordl50, a Small Pin Holel09, which is shown in Fig.4 and which has a diameter of 0.1 mm, is so drilled that the core of Zr ferrulel40 of HMS connectorl32 of the First MM Optical Fiber Patch Cordl50 is centered with this Small Pin Holel09 and the Pulsed Gaussian Laser Beams501 of Pulsed Type Laser Source500, Chopped Gaussian Laser Beams601 of Chopped Type Laser Source600, and CW Gaussian Laser Beam799 of CW Laser Source800 is first oriented to this Small Pinholel09 during PE _av 840, PE^ ^{f clem} 845, and R _CIS 320 measurements by means of Alignment Combinationl62 by directly observing the relative output signal level of the Second Photodiodel29 linked to Fast Response Current to Voltage Converterl27 on the screen of the 0scilloscopel30. The maximum signal on the screen of the 0scilloscopel30 is Po'401 in Fig. 3 during PE _av 840, and 845 measurements of Pulsed Type Laser Source500, and Chopped type Laser Source600, and the maximum signal on the screen of the Oscilloscope 130 is pew max _{198 for cw Laser} source800 as in Fig.8 during the determination of R^ _CIS 320. In the invention, because Chopped Type Laser Source600 is generated from CW Laser Sources800 by using a series of choppers901-909, the optical axes coinciding process can be made directly by using CW Laser Source800 without chopping CW Laser Gaussian Beams799 just before measuring ^clem 845. This point is clarified in the Section "c-) Calibration of a Commercial Laser Energy Meter by using chopped type laser source". The Gaussian Laser Beams 501, 601, 799 of Pulsed Type Laser Source500, Chopped Type Laser Source600, and CW Laser Source800 reflected from the inner surface of the Small Steel HemispherellO are repetitively reflected towards nearly same region of FCISIOO, labeled as the first reflectionl49 in Fig.4, and this provides us with higher repeatability and reproducibility of optical axis alignment processes in measurements of I _av 300, ^cIem 842, and I ^res P 200 yielding the results of PE _av 840, PE^ ^{f clem} 845, and Rpcis ³²⁰ together with the time/frequency related measurements T _av 330, f _av 331, T _a ^r v ^{f clem} 844, and f _a ^r v ^{f clem} 843 to be performed by the Second Photodiodel29. T _av 330, f _av 331 are related parameters to PE _av 840, which is the averaged pulse energy of Pulsed Type Laser Source500. _T ref_ciem _{844) and f} ref_ciem _{843 are related} parameters to PE^ ^{f clem} 845, which is the reference and averaged pulse energy of Chopped Type Laser Source to be used in the calibration of Commercial Laser Energy Meter999. For CW Laser Source800 in Fig.8, which has identical beam waist and divergence properties those stated in this invention, typically, an optic power of pcw_res _P≡ 4 _m w 201 of CW Gaussian Laser Beam799 of CW Laser Source800 entering from Port_1101 of FCISIOO, and falling on the center of the Small Steel HemispherellO, the launched optical power P ₀ ^{cw max} 198 in the First MM Optical Fiber Patch Cordl50 through Small Pin Holel09 having a diameter of 0.1 mm stimulates a maximum DC voltage of 10 mV at the output of Fast Response Current to Voltage Converterl27 joined to the Second Photodiodel29 as in Fig.8, which is tracked on the screen of 0scilloscopel30 in real time and during all the measurements in the invention. This also corresponds to a pulse peak power Po' of 10 mV 401 for Pulsed Type Laser Source500, and Chopped Type Laser Source600. It is said that a maximum DC voltage -10 mV on the 0scilloscopel30 screen matching an optical power of pcw_res _P≡ 4 mW 201 corresponds typically to the best condition of the optical alignment between the optical axis of CW Laser Source800 and the optical axis398 of FCISIOO of FCIS based-LEMCSlll for the Port_1101, which is a circular aperture of 8 mm diameter in the invention. These typical values are given for how to operate the optical alignment procedure of FCIS based-LEMCSlll in the invention.

Small Steel HemispherellO, in the center of which Zr ferrulel40 of HMS connectorl32 of the First MM Optical Fiber Patch Cordl50 is placed, is inclined, i.e. 25°, towards the opposite wall of the First Photodiodel20 in order to prevent the First Photodiodel20 from the first reflections of Pulsed Gaussian Laser Beams501 of Pulsed Type Laser Source500 and Chopped Gaussian Laser Beams601 of Chopped Type Laser Source600 falling onto the First Photodiodel20 as shown in Fig.4. The diameter of the Small Steel HemispherellO is 13 mm and the circular target area of the Small Steel HemispherellO is A _S h= π (13/2) ² = 133 mm ² 520. Due to the fact that the Small Steel HemispherellO is inclined as i.e. 25° towards the opposite wall of the First Photodiodel20, the Gaussian Laser Beams501,601,799 entering from Port_1101 doesn't see an enclosed circular area of A _S h=133 mm ² 520. Instead of 133 mm ² , Port_1101 sees an effective circular area of 133 mm ² xcos (25°) = 120.54 mm ² .

The inner surface of Small Steel HemispherellO is mechanically and chemically polished/mirrored. The increasing of the reflectivity of the inner surface of Small Steel HemispherellO with the polishing processes prevents the inner surface of Small Steel HemispherellO from the temperature increase, to be caused by Pulsed Gaussian Laser Beam501 of the Pulsed Type Laser Source500 and Chopped Gaussian Laser Beam601 of Chopped Type Laser Source600, interior surface of Small Steel HemispherellO. The penetration dept of the electromagnetic energy the interior polished surface of Small Steel HemispherellO is infinitesimal small and the electric fields of Pulsed Type Laser Source500 and Chopped Type Laser Source600 induces the surface electric charges on the infinitesimal small surface depth on the polished/mirrored surface of the Small Steel HemispherellO. This directly corresponds to no electrical charge inside the Small Steel HemispherellO and secondary electromagnetic waves are induced by the surface charges vibrating with an optical frequency identical to that of Pulsed Type Laser Source500 and Chopped Type Laser Source600. The secondary wave propagation of the Pulsed Type Laser Source500 and Chopped Type Laser Source600 reflected from the interface air/Small Steel HemispherellO inner surface and Zr ferrulel40, the melting point of which is 1855 °C, gives rise to a scattering wave and so is reflected to the opposite wall of the First Photodiodel20 inside FCISIOO with the inclination of Small Steel HemispherellO, i.e. 25° in the invention. The absorption of electromagnetic wave in a metal takes places in consistent with Paul Drude's model, based on the idea that free electrons first accelerated with electrical field of electromagnetic wave in the metal are damped with phonon collisions together with other lattice imperfections, and is strong functions of polarization of electromagnetic wave, incidence angle of beam, surface properties such as roughness, frequency of electromagnetic wave, electrical conductivity of the metal, and the temperature of the metal. In Fig.5, the penetration depth is demonstrated by dark gray such as an evanescent wave penetration inside stainless steel. In three dimensional spaces, the absorbing volume of stainless steel can be regarded as a cone for the estimation of energy transferred into stainless steel body via way of heat conduction and the temperature increases inside stainless steel body of Small Steel HemispherellO. In addition to Paul Drude's model, Fresnel Formulas, which are written for wavelength dependent p- and s- polarization states in terms of optical constant of the mentioned metal, also work for absorption properties of the mentioned metal surface. For visible and IR electromagnetic fields, the penetration depth of electromagnetic wave in the metal is approximately a few tenths of nanometer. However, the typical penetration depth, in which the electromagnetic energy is strongly absorbed, is assumed as the order of a few hundreds of nanometers by considering the surface roughness, the impurities, the oxide content, the surface temperature and the possible surface defects of the inner polished surface of Small Steel Hemisphere, all of which cause the incoming light beam of Pulsed Type Laser Source to be trapped inside metal body, giving rise to temperature increase inside the stainless steel body. Therefore the calculations in the invention, it can be assumed that the relevant laser energy is confined and absorbed within a few hundred nanometers of the inner surface of Small Steel Hemisphere taking the surface roughness and other affecting parameters mentioned above into account. For an IR laser of 980 nm, the penetration depth of 500 nm together with the surface roughness, the impurities, the oxide content, the surface temperature and the surface defects, which strongly affect the absorbance of the electromagnetic energy in the metal is a realistic approach, which is seen in the data obtained from atomic force microscope inspections and Monte Carlo Simulation results [6]. The "penetration depth" term stated in this part should be regarded as a confined volume of inner polished surface of Small Steel Hemisphere, in which any Pulsed Gaussian Laser Beam is strongly absorbed and is directly converted into temperature increase inside Small Steel Hemisphere. One of the critical point in this invention is to calculate the temperature increase in the confined volume of the Small Steel HemispherellO which is enclosed by the beam size of the Pulsed Type Laser Source on the target point of the Small Steel Hemisphere and the penetration depth of 500 nm with some degree of surface roughness. The beam sizes of Pulsed Type Laser Source500 and Chopped Type Laser Source600 on the target of the Small Steel HemispherellO corresponds to the base diameter of cone and it is calculated as 2.72 mm for 980 nm at the worst case. By assuming that the enclosed volume in body of Small Steel

SHM

HemispherellO is a cone volume V _cong , not a cylinder, the following calculations are carried out for the worst case and scenario. The maximum single pulse energy PE™ ³ which corresponds to the maximum value of the pulse energy of Pulsed Type Laser Source500, is 100 mj, the typical total (specular plus diffuse) reflectance of inner surface of Small Steel HemispherellO, which is chemically and mechanically mirrored/polished, is 95% for near IR region of the electromagnetic spectrum. The melting point of stainless steel, the material of the Small Steel Hemisphere, is 1510 °C. The specific gravity of stainless steel p _steel , from which the Small Steel HemispherellO is manufactured, is 7850 kg/m ³ . The specific heat of stainless steel c _stee j is 490 J/(kg K) and the thermal conductivity, a function of electron mobility inside metal, is 23 W/(m K).

SHM i 2

V cone = - 3 π Beam Waist Radius . Penetration Dep ^" th (16) ^J

SHM SHM

The volume V cone and the mass m cone of the cone, in which electromag °netic field of

Pulsed Type Laser Source500 penetrates, is calculated as follows;

SHM 2.72 mm „ .„-12 _¾

V cone = - 3 ί 2 Y 500 nm = 0.93x10 m ³

SHM SHM n o , e

m = v

cone cone . ' s,tee ,l= 0.93xl0- ¹² m ³ 7.85xl0 ⁶ - _m ¾3 = 0.73xl0- ⁵ g o

For a single pulse of 100 mj, the temperature increment is calculated by Q = m∞ _n ^M _e . c _steel . AT(K) (17)

The reflection of the mirrored surface of Small Steel HemispherellO is -95%. In this case the absorbed energy by stainless steel for PE™ ³ of 100 mj is around pE ^absorb = 5 mj. The temperature increment ΔΤ resulted from a absorbed energy pE ^absorb of 5 mj inside the enclosed cone volume of stainless steel is, ΔΤ = — = 1398 K

(0.73x10-^ _{g) (49} o _i -i^ ₎

When the temperature increment of 1398 K caused by a PE™ ³ of 100 mj inside the enclosed cone volume in the body of the Small Steel HemispherellO, this temperature increment is dissipated inside all steel body of the Small Steel HemispherellO, the total mass of the Small Steel HemispherellO 13 g, and it has a surface area of 3.9 cm ² (2.1 cm x 1.85 cm and its thickness is 3 mm) behaving as a heat sink for the enclosed cone volume of the Small Steel HemispherellO. The heat transfer from hotter region to the surrounding and cooler region inside the stainless steel body behaving as a heat sink for the enclosed cone volume of the Small Steel HemispherellO takes places with electron mobility and so the average electron velocity is a determinative parameter for thermal conductivity. If the heat transfer rate by heat conduction process inside stainless steel of the Small Steel HemispherellO is known, it is possible to calculate the time elapsed for decreasing the temperature increment of 1398 K to any reasonable temperature level not damaging the material and surface conditions of the Small Steel HemispherellO. When the Pulsed Gaussian Beam of Pulsed Type Laser Source having a maximum pulse energy PE™ ³ of 100 mj collides on the stainless steel with a beam diameter of 2.72 mm of 980 nm laser by assuming the temperature of the Small Steel HemispherellO is in thermal equilibrium for the room temperature of 25 °C equal to 298K, the temperature on the target diameter of 2.72 mm of the stainless steel reaches 298 K + 1398K = 1696 K, corresponding to 1423 °C. The energy transfer rate Q _co with conduction in (J/s) is

Where k is thermal conductivity of stainless steel and equal to 23 W/(m K). A is surface area of Small Steel HemispherellO behaving as a heat sink, and equal to 3.9 cm ² and x is the thickness of the stainless steel constituting the Small Steel Hemisphere and equal to 3 mm. ΔΤ' is the temperature difference of stainless steel before and after heat dissipation. Now the instant temperature value on the target diameter of 2.72 mm of the stainless steel, once maximum single laser pulse energy PE™ ³ of 100 mj of Pulsed Type Laser Source falls, is 1423 °C. A temperature difference of ΔΤ' = 1000 K can be reasonable value for not damaging the inner surface of the Small Steel HemispherellO. From Eq.(18), the energy transfer rate with conduction inside the steel body of the Small Steel Hemisphere is Q _co = 2990 J/s, and finally the energy of 5 mj absorbed by stainless steel is dissipated within (5 (mJ)/2990 (J/s) =1.7 μ≤) in body of the Small Steel HemispherellO. The whole mass of the Small Steel HemispherellO is 13 g and the temperature increase inside whole body of the Small Steel HemispherellO can be estimated as in Eq.(19) by assuming that the temperature gradient is uniformly distributed inside the volume of the Small Steel HemispherellO,

Q = PE ^absorb = 5 mj = mg _sin , c _steel . ΔΤ" (19) The volume of the stainless steel behaving as a heat sink is equal to multiplication of the surface area of 3.9 cm ² (2.1 cm x 1.85 cm) with the thickness of 3 mm, yielding 1.17 cm ³ . The mass behaving as a heat sink mj^ _t ! sink * ^s obtained by multiplying 1.17 cm ³ with stainless steel specific gravity p _steel , 7850 kg/m ³ , yielding m^™ _S ink ⁼ 9.1845 g. P _E absorb ₌ 5 _m j ₌ 9.1845 g. 490 J/(kg K). ΔΤ" (20)

It should be remembered that 5 mj is directly corresponds to a pulse energy of 100 mj because of the averaged reflectivity of 95% of the mirrored inner surface of Small Steel HemispherellO. Resultantly, temperature increase is ΔΤ" = 1.1 mK for each laser pulse, PEj ^of which is 100 mj. The result inferred from these calculations the Small Steel Hemisphere easily withstand the laser pulse train composed of the maximum single laser pulse energies up to PE™ ³ = 100 mj without any degradation, if the dead time DT312 is wider than 1.7 μ≤ between two adjacent laser pulses, PE^of which is 100 mj . If the dead time DT312 between two adjacent pulses in Fig.3, each of which has a PE™ ³ of 100 mj, is narrower than 1.7 μ5, this doesn't allow the single pulse energy inside the body of Small Steel HemispherellO behaving as a heat sink to dissipate sufficiently. In other words, to apply any pulse train having the dead time DT312, which is narrower than 1.7 μ5, between two adjacent pulses, each of which has a PE™ ³ of 100 mj, increases the instant temperature of the body of the Small Steel HemispherellO, as a function of repetition frequency of Pulsed Type Laser Source500. On the other hand, if it is assumed that Pulsed Type Laser Source has a repetition frequency of 1 MHz and it has a PE™ ^ax of 100 mj, which matches a peak power P ₀ 400 of 200 kW for PW310=0.5 μ5, this is equal to 500,000 pulses per 1 sec (five hundred thousand pulses), in this case of Dead Time (DT312) = 0.5 μ≤ <1.7 μ5, the temperature increases quickly inside the volume of the stainless steel behaving as a heat sink and approaches to 500,000 x 1.1 mK = 550 K for pulse application of 1 s, which is the worst case. When the pulse energy increases, it is necessary to make DT312 between two adjacent laser pulses be larger than 1.7 μ≤ so as to obtain sufficient heat dissipation. However it should be remembered that the maximum average power, which corresponds to the maximum value of the averaged optical power P _av 301 in Fig.3, which enters from the Port_1101 of FCISIOO, and which corresponds to the saturation power for the First Photodiodel20 of 7 mW, should be P ³ ½158 W, which is a value from the ration of the active area of the First Photodiodel20 to the inner surface area of 4nR ² of FCISIOO. In this case in order to measure to the peak power P ₀ 400 of 200 kW via FCIS without saturation of the First Photodiode, the pulse width (PW310) of the peak power P ₀ 400 of 200 kW should be 1.35 ns and the dead time (DT312) should be any value wider than 1.7 μ≤ for sufficient heat dissipation inside stainless steel body. However, it is seen from Eq.(9), and Eq.(10), the rise time of the First Photodiode is 1 MHz and as a consequence, 1.35 ns pulse having a peak power Po=200 kW400 cannot be detected by the First Photodiodel20 owing to the pulse response limit of 0.736 μ≤ of the First Photodiodel20 in Eq.(9). NOTE: The above calculations regarding time duration, -which is pulse dead time (DT) of infinite laser pulse train,- necessary for the sufficient dissipation of the absorbed heat resulted from the temperature increase, which is caused by the maximum pulse energy PE™ ^ax of Pulsed Gaussian Laser Beam of Pulsed Type Laser Source, inside the body of Small Steel Hemisphere used as a target in the invention are to give an exact method for the question of how to calculate time duration (dead time-DT) between two adjacent pulses, each of which has a maximum single pulse energy PE™ ^ax of 100 mj, during the application of maximum single pulse energy PE™ ^ax of 100 mj without damage on the inner surface of Small Steel Hemisphere. Reflectance, penetration depth, surface roughness, temperature of metal surface, specific heat of metal may change within very wide range, as well as electromagnetic wave properties such as wavelength, incident angle and its state of polarization. Any change in the numerical values of these parameters that strongly affect the above calculations doesn't disturb the philosophy of the invention, the correctness of the above calculations and the presented method.

Now here we can construct the correct limit conditions for the FCIS based-

LEMCS111 for the parameters belonging to Pulsed Type Laser Source. The parameter here are averaged values: PW™ ⁿ , which is the minimum value of PW _av 342; PW™ ^ax , which is the maximum value of PW _av 342; DT™ ⁿ , which is the minimum value of DT _av 340; T™ ⁿ , which is the minimum value of T _av 330; Ρ^, which is the saturation value of P _av 301 for the First Photodiodel20; and P ₀ ^max which is the maximum value of P ₀ 400 of the maximum peak power of either Pulsed Type Laser Source in Fig.3: According to the assessments given just below Eq.(9), PW™ ⁿ should be equal to or larger than 736 ns for time response of the First Photodiode, DT™ ⁿ should be equal to or larger than 1.7 μ≤ for sufficient heat dissipation at the maximum pulse energy of PE™ ^ax = 100 mj from the above evaluations together with those in Fig.(4). Finally, the maximum averaged saturation power P _a ^sat , which can be measured by FCIS based-LEMCSlll without saturation of the First Photodiodel20 is calculated as 158 W from the surface ratios of FCISIOO interior surface area and active area of the First Photodiodel20. Resultantly, by using Eq.(4) for an infinite laser pulse train having a period of T™ ⁿ = PW™ ⁿ + DT™ ⁿ = 0.736 μ≤ + 1.7 μ≤ = 2.436 μ≤ and we can calculate the maximum peak power P ₀ ^max to be measured through FCIS based-LEMCSlll for an infinite laser pulse train having an averaged Duty Cycle _av 299 as in Eq.(5),

pmax _pw min _p max( _{n 7 fix1 n} -6 _<

P™ ^aX = 158 W = ° _mln ^a _in = ^P ° (0.736X10 sj a ^v PW™ ⁿ +DT™ ⁿ (0.736X10- ⁶ S + 1.7X10 ^"6 s) ^{L J}

An infinite laser pulse train having a maximum peak power P ₀ ^max =522 W calculated from Eq.(21), the PW™ ⁿ of which is 0.736 μ≤ and the DT™ ⁿ of which is 1.7 μ≤ creates an averaged pulse energy PE _av 840 of ~ 384 μ] on FCIS based-LEMCSlll and it can be measured without damage on Small Steel Hemisphere surface and without saturation of the First Photodiode. For the maximum averaged pulse energy PE^of 100 mj of FCIS based- LEMCS111, the maximum pulse width PW™ for the maximum peak power P ₀ ^max of 522 W of Pulsed Type Laser Source, which can be detected by the First Photodiodel20 without saturation, is calculated by dividing PE™^ =100 mj with P ₀ ^max =522 W and the result is PW™ ^ax ≡1.9xlO- ⁴ s.

In brief, the ultimate limit parameters for measuring the averaged pulse energy of Pulsed Type Laser Source500, which FCIS based-LEMCSlll in the invention can measure, are summarized as minimum averaged pulse width, PW™ ⁿ ≡ 0.736 μ5, averaged minimum dead time, DT™ ⁿ ≡ 1.7 μ5, producing a minimum repetition period of T™ ⁿ ≡2.436 μ5, corresponding to an averaged repetition frequency of f™^ = 1/T™ ⁱⁿ = 410509 Hz and the maximum pulse width, PW™ ^a ½ 1.9xl0" ⁴ s for a maximum peak power P ₀ ^max ≡522 W, which can be detected by the First Photodiode without saturation and the averaged saturation power for the First Photodiodel20 is P _a ^sat ≡158 W.

Mechanical Attenuatorl70, which is joined to the ceramic ferrule of FC/PC connector of the first MM optical fiber patch cordl20, is used to attenuate the some portion of the Pulsed Gaussian Laser Beam501 launched into Zr ferrulel40 of HMS connectorl32 of the First MM Optical Fiber Patch Cordl50 assembled with Small Steel HemispherellO. In this invention, although the limited numerical aperture of 0.25 rad of the optical fiber core of Zr ferrulel40 of the First MM Optical Fiber Patch Cordl50 inherently protects the Second Photodiodel29, a Mechanical Attenuatorl70 is also engaged for an additional protection of the Second Photodiodel29 against high level of optical power exposure during time and frequency measurements of the Pulse Type Laser Sources500 having a relatively high peak power. Due to the fact that the Second Photodiodel29 is only used for time/frequency related measurements, Mechanical Attenuatorl70 is kept on high attenuation position. High attenuation position of Mechanical Attenuatorl70 is reduced to low attenuation position by observing the voltage on the screen of the Oscilloscopel30, PE _av (fav)840 value of which is to be measured, until the pulse levels of Pulsed Type Laser Source500 are seen on the screen of the Oscilloscopel30. When the sufficient pulse level is seen on the screen of the Oscilloscopel30, the averaged repetition period T _av 330 and the averaged repetition frequency f _av 331 of Pulsed Type Laser Source in Eq.(16) are measured directly by the combination of the Second Photodiodel29, Fast Response Current to Voltage Converterl27, and Time Interval Counterl35 in Fig.l, which is calibrated traceable to ¹³³ Cs (or ⁸⁷ Rb) Atomic Frequency Standard804, in average mode.

The Second Photodiodel29 is used for the time measurements, cutoff limit is 6 GHz and the cutoff limit of the successive Fast Response Current to Voltage Converterl27 is 10 GHz. Because FCIS based-LEMCSlll described in this invention is a preferred embodiment, the upper cutoff frequencies are acceptable and better than 1MHz and 6 GHz for both photodiodes designated as the First Photodiodel20 and the Second Photodiodel29. Additionally, both photodiodes called as the First Photodiodel20 and the Second Photodiodel29 herein can be exchanged with different types of semiconductor detector depending on the spectral power distribution of the laser in the application. Types of CW Laser Sources800 which are used for constructing Chopped Type Laser Sources600, generating the reference and averaged pulse energyPEg ^clem 845, in FCIS based-LEMCSlll, which is to be engaged in the traceable calibration of Commercial Laser Energy Meters999, are not included in the invention. However, the compatibilities and the dimensional relationships of the following parameters in terms of their sizes, and their locations together with the measurement and the calibration methods to be explained in Section "3. Measurement Method of pulse energy of Pulsed Type Laser Source and calibration of Commercial Laser Energy Meter by FCIS based-LEMCS" are included in the invention. The compatibilities and the dimensional correlations to be included in the invention, which are the additions to the three main ideas/items given at the end of "DESCRIPTION" section, are;

a-) the geometrical dimension of Port_1101 with respect to full sizes of beam of Pulsed Type Laser Source500, Chopped Type Laser Source600, and CW Laser Source800 entering from Port_1101, and their beam waists,

b-) beam divergences of Pulsed Type Laser Source500, Chopped Type Laser Source600, and CW Laser Source800 starting from z=0, depending on the distance on the Optical Axis398 with respect to size and location of the Small Steel HemispherellO,

c-) the size of Small Steel HemispherellO with respect to the size and dimension of FCISIOO of FCIS based-LEMCSlll, its angular inclination and its position with respect to Port_2102,

d-) the position of Zr ferrulel40 of HMS connectorl32 of the First MM Optical Fiber Patch Cordl50 assembled with the Small Steel HemispherellO at Port_3 with respect to position of Port_1101 for Pulsed Gaussian Laser Beam501, Chopped Gaussian Laser Beam 601, and CW Gaussian Laser Beam799 beam entering from Port_1101 and having the calculated beam divergences.

2. Details of Choppers

A series of the choppers901-909 of FCIS based-LEMCSlll invented are used for constructing Chopped Type Laser Source600 generating the reference and averaged pulse energies PE _ay ^{f clem} 845 for the calibration of Commercial Laser Energy Meters999 traceable to primary level standards by chopping the CW Gaussian Laser Beams799 of CW Laser Sources 800 in Fig.2. which are called the first CW Laser_l, the second CW Laser_2, the third CW Laser_3, and the fourth CW Laser_4- These CW Laser Sources800, at same time, are operated in the determination of the spectral responsivity Rpcis 320 of FCISIOO of FCIS based-LEMCSlll in CW regime/mode, shown in Fig.8. With the choppers901-909 used in this invention, the CW Gaussian Laser Beams799 of the first CW Laser_l, the second CW Laser_2, the third CW Laser_3, and the fourth CW Laser_4 are chopped with variable Duty Cycles322. The Duty Cycles changing from 0.17 to 0.84 via DC Motor599 having High Quality Rare Earth Doped Magnet are obtained for the repetition frequencies321 (f=l/T), from 5 Hz to 2 kHz in the calibration of Commercial Laser Energy Meter999 against FCIS based-LEMCSlll in Fig.2. The adjustment of Duty Cycle continues up to 2 kHz via a DC Motor599. Modulation frequency depends on the angular rate generated by the DC motor and the Duty Cycle322 at any modulation frequency generated via DC Motor599 relies on the angular slit of any chopper joined to DC Motor599. The combination of the explained choppers901-909, CW Laser Sources800 and DC Motor599 having High Quality Rare Earth Doped Magnet in FCIS based-LEMCSlll forms the infinite laser pulses having stable pulse energies stated as the reference and averaged pulse energy PE^ ^clem 845 for calibrating Commercial Laser Energy Meters999 in Fig.2 and N is equal to 1 for the infinite laser pulses in time domain.

In this invention, the different repetition periods T(s) 320 of the chopped Gaussian Laser Beams having an Duty Cycles299 varying 0.17 to 0.84 are generated, these repetition periods T(s) 320 are precisely measured by removing the negative effects of time constant of FCISIOO and the relatively lower cutoff frequency of the First Photodiodel20 by means of new placement type of the Second Photodiodel29 mounted to the FCISIOO. Finally a new method and a new configuration of integrating sphere, called FCIS in this invention, are put into progress to calibrate the pulse energy pg ^cie mQj scales of the Commercial Laser Energy Meters999.

The chopper901-909 details used in FCIS based-LEMCSlll are given in the drawings separately, from Fig. 6a to Fig. 6b. The metal coppers901-909 used in this invention are made from stainless steel and engraved by means of a computer controlled-laser cutting machine with high precision. The choppers901-909 are so designed that they have 15 periods in one complete turn and each period is 24°. The full diameter of each chopper901-909 is 106 mm, the thickness of each chopper901-909 is 1 mm. The closed section of the chopper901-909 generating a Duty Cycle322 of 0.83 in Fig.6a is so designed and engraved that the CW Gaussian Laser Beam799, which has a beam waist of 2.8 mm at z=0, corresponding to the widest beam waist used herein, is completely blocked. The averaged Duty Cycle is Duty Cycle _av 299 measured as an averaged value by Time Interval Counterl30 and it is considered as time/frequency related measurements in the invention. The open section of the chopper901-909 generating a Duty Cycle322 of 0.17 in Fig.6b is so designed and engraved that the CW Gaussian Laser Beam799, which has a beam waist of 2.8 mm at z=0, is completely passed. With this mechanical chopping process, the zero level of Chopped Gaussian laser beam, the PE _a y ^f - ^clem 845 of which is to be measured, is exactly generated and as a result, the leakage (background) current in I^ ^clem 842 caused by exactly not zeroing the optical power to be entered in FCISIOO of FCIS based-LEMCSlll is prevented and the undesired contribution at the leakage (background) current in I^ ^clem 842, which electronic modulation may cause this type error because of the insufficient reversed bias, is removed for each Duty Cycle322 at any averaged repetition frequency 843and this uncertainty source is disregarded with mechanical chopping processes, generated by the choppers detailed in drawings referred as Fig.6a and Fig.6b. If an electronic modulator is used for applying pulse modulation to any laser operating in CW regime/mode, the zero level of the Pulsed Gaussian Laser Beams501 should be considered and subtracted in the calculation as a background (leakage current). If this background (leakage) current level due to not zeroing the output of modulated Gaussian laser beams with the electronic modulation is not considered, it causes wrong pulse energy calculations and it increases the measurement uncertainty in the calibration of Commercial Laser Energy Meter999. However, the use of a series of the chopper 901- 909 in producing the Chopped Gaussian Laser Beams 601 of Chopped Type Laser Source600 in this invention prevents the problematic and the undesired condition and reduces the measurement uncertainty caused by not getting zero level.

Jitter of the DC Motor599, to which the choppers901-909 is mounted as in Fig.2, and which has a rare earth doped magnet, has an RMS value of 0.2° at 1 KHz. This value is obtained, comparing a reference frequency of 1 KHz with the Chopped Gaussian Laser Beams601 coming from the chopper having 0.5 Duty Cycle322, by Time Interval Counterl30. For the constant peak powerP ₀ 400 of the Chopped Gaussian Laser Beam601 as in Fig.3, the maximum and minimum pulse energy to be generated by means of the chopper configuration, depending on the repetition frequency f(Hz)321, the repetition period T(s)320, dead time DT(s)312, pulse width PW(s)310, and Duty Cycle322 in the invention are given at the following.

The repetition frequency f (Hz)321 range, over which Commercial Laser Energy Meters999 are calibrated in FCIS based-LEMCSlll in this invention extends from 5 Hz to 2 kHz by means of the nine separate choppers for the Duty Cycle322 ranges 0.17 to 0.83 shown in Fig.6a. and Fig. 6b. In this case the maximum energy via these choppers901-909 to be engaged in the calibration of Commercial Laser Energy Meter999 in FCIS based-LEMCS is calculated as follows. Superscript "_clem" shows the relevant parameter in the calibration of Commercial Laser Energy Meter999.

For the repetition frequencies f (Hz)321 which corresponds to the averaged repetition frequency f _av 331, f « f^ _g in Eq.(16);

_T ref_clem_maxiref_clem ,ref_clem

p pref_clem_max _ _| 'av _ 'av rn f ? ?~| a pmin fref clem min Ririin U J

^K FCIS ^{r " " K} FCIS

In order to produce the maximum energy for the constant peak power P ₀ 400 by means of the combination of one of the choppers901-909 and DC Motor599 in the invention, the maximum pulse width pw ^ref - ^clem - ^max corresponding to the minimum repetition frequency f ^{ef clem} - ^min _at maximum duty cycle Duty Cycle ^ref - ^clem - ^max should be adjusted and in the case of maximum pulse width pw ^ref - ^clem - ^max , Iav ^{f clem} 842 is obtained as the maximum photocurrent I^ ^f - ^clem - ^max in the First Photodiodel20 of FCIS100. According to CW Laser Source800 used in this invention, Rp s, which corresponds to the minimum value of Rpcis 320, is equal to the spectral responsivity of FCISIOO at 980 nm, which is changeable value from application to application.

fref_clem_min Duty Cycle ^ref - ^dem - ^max

¹ p _W ref_clem_max L ^HZ J I "J In this invention the minimum repetition frequency f ^{ef clem min} = 5 Hz, corresponding the maximum repetition period T ^{ref clem MAX} = 200 ms and Duty Cycle ^ref - ^clem - ^max = 0.83 for the chopper901 given in Fig.6a, the corresponding the maximum pulse width pw ^{ref CLEM MAX} = 200 ms x 0.83 = 166 ms. The final equation for Eq.(22) is

. , _pw ref_clem_max ,ref_clem_max

ppref_clem_max _ 1 £L (\Λ (74Λ a ^v Duty Cycle ^ref - ^clem - ^max R¾¾ ^{U J L J} Minimum energy for these choppers901-909 to be engaged in the calibration of Commercial Laser Energy Meter999 in FCIS based-LEMCSlll is calculated as follows;

For the averaged repetition frequencies f (Hz)321, which corresponds to the averaged repetition frequency f _av 331, f « f^dB ^m Eq.(16);

_T ref_clem_miniref_clem ,ref_clem

ppref_clem_min _ _ 'av _ 'av rn ( ^Λ a pmax f ref clem max R max UJ L^ ^J

^K FCIS ^{r " " K} FCIS

In order to produce the minimum energy for the constant peak power P ₀ 400 by means of the combination of one of the choppers901-909 and DC Motor599 in the invention, the minimum pulse width pw ^ref - ^clem - ^min corresponding to the maximum repetition frequency f ^{ef clem max} _a t the minimum duty cycle Duty Cycle ^{ref clem min} should be adjusted and in the case of the minimum pulse width pw ^ref - ^clem - ^min , I _a ^clem 842 is obtained as the minimum ^ ^clem - ^min in the First Photodiodel20 of FCISIOO. According to CW Laser Source800 used in this invention, , which corresponds to the maximum value of R _FCIS 320, is equal to the spectral responsivity of FCISIOO at 1549 nm, which is changeable value from application to application.

f _. dem max ₌ Duty Cycle ^ref - ^dem - ^ml "

p ref_clem_min J In this invention the maximum repetition frequency f ^{e c em max} = 2 kHz, corresponding minimum repetition period T ^{REF CLEM MIN} = 0.5 ms and Duty Cycle ref_ciem_min ₌ Q.17 for the chopper909 given in Fig.6b, the corresponding the minimum pulse width p _W ref clem min ₌ Q 5 _{MS Χ} Q _± J _{= Q QQS ms The fmal equation} f _or Eq.(25) IS,

In order to protect the operator from the laser beam reflected the closed section of the relevant chopper901-909, the suitable protection equipments for both body and eye safety should be used. The changing of these values presented here doesn't disturb the philosophy of this invention because FCIS based-LEMCSlll and the calibration method of Commercial Laser Energy Meter999 against FCIS based-LEMCSlll traceable to primary level standards are preferred embodiments.

3. Measurement Method of pulse energy of Pulsed Type Laser Source and calibration of Commercial Laser Energy Meter by FCIS based-LEMCS

This section comprises the following parts;

The section "Determination of the spectral responsivity Rpcis °f FCIS based- LEMCS" describes the method of determining the spectral responsivity Rp _CIS 320 of FCISIOO of FCIS based-LEMCS with respect to the Optical Power Transfer Standard809 calibrated against Cryogenic Radiometer803 in near IR region by using CW Gaussian laser beam799 of CW Laser Source800 in Fig.8.

The section "Method of measuring the averaged pulse energy PE _av of a Pulsed Type Laser Source by means of FCIS based-LEMCS" describes the method of measuring the averaged pulse energy PE _av 840 with pulsed Gaussian laser beams of a Pulsed Type Laser Source500 emitting in near IR region covering the spectral range in the invention, in which the spectral responsivity Rpcis ^{320 of} FCISIOO of FCIS based-LEMCSlll is determined, in Fig.l. Due to the fact that the FCIS based-LEMCSlll is constructed as a preferred embodiment, the changing in the spectral region specified as near IR above doesn't change the philosophy of the invention.

The section "Calibration of a Commercial Laser Energy Meter by using Chopped Type Laser Source in FCIS based-LEMS" describes how to calibrate any Commercial Laser Energy Meter against the chopped Gaussian laser beams601of Chopped Type Laser Source600 generated by means of the combination of CW Laser with the nine separate choppers as an infinite wave train, the averaged pulse energy PE^ ^cIem 845 of which was measured by FCIS based-LEMCS, generating a calibration factor called γ 945 as in Fig.2. These methods described in this section are included in this invention.

a-) Determination of the spectral responsivity Rpcis of FCIS based-LEMCS;

In this invention, in order to determine the averaged pulse energy PE _av 840 of Pulsed Type Laser Source500 and to determine the averaged pulse energy PE^ ^clem 845 of Chopped Type Laser Source600, the configurations of FCIS based-LEMCSlll illustrated in Fig.l and Fig.2 are used for directly measuring the average photocurrents I _av 300 and Ia - ^Clem 842 related to the averaged pulse energies PE _av 840 and PEav ^{f clem} 845 emerging from the Pulsed Type Laser Source500 and Chopped Type Laser Source600 by means of the First Photodiodel20 in turn, and are used for directly measuring the average repetition periods T _av 330 and Ta _y ^f - ^clem 844 and the average repetition frequencies f _av 331 and fref ^c iem 54.3 ₀ f p _u i _se( j Type Laser Source500, and Chopped Type Laser Source600 by means of the Second Photodiodel29 of FCISlOO of FCIS based-LEMCSlll. In order to calculate the pulse energies of Pulsed Type Laser Source500, and Chopped Type Laser Source600, the spectral responsivity Rpcis 3 0 of FCISlOO of FCIS based- LEMCSlll assembled with the First Photodiodel20 is required. For a continuous type laser designated as CW Laser Source800 herein, meaning not modulated in time domain and so not containing no additional frequency component related to the modulation in time domain, the average optical power is the same as its peak power and the same case is valid for the average photocurrent and the peak photocurrent as well. After this brief and repeated evaluation, the determination of spectral responsivity Rpcis 320 of the First Photodiodel20 of FCIS based-LEMCS is accomplished with the configuration in Fig.7. Superscript "resp" shows the relevant parameter in the determination of spectral responsivity R _FCIS 320 of FCISlOO of FCIS based-LEMCS. In determination of R _FCIS 320 the setup of FCIS based-LEMCS shown in Fig.8 is configured. The CW Gaussian laser beam799 of CW Laser Source800 is not chopped, and the optical power of CW Laser Source pcw resp 201 directly is fallen in FCISlOO in the continuous regime (CW). In this condition, FCISlOO of FCIS based-LEMCS works as a conventional integrating sphere, except for Small Steel Hemisphere assembled with the Second Photodiode designed in the invention. The First Photodiodel20 produces the photocurrent I ^res P (A) 200 proportional to the optical power of CW Laser Source pcw_res _P (W)201, which is measured by means of Optical Power Transfer Standard809. I ^res P (A)200 measured by the First Photodiodel20 is traceable to DC Josephson Voltage System801 and Quantum Hall Resistance System802 through Electrometerll9 shown as in Fig.7 and Fig.8. The same CW Gaussian laser beam799 of CW Laser Source800 is fallen onto Optical Power Transfer Standard809 shown in Fig.8 and Fig.7, and then pcw resp j _s obtained as a traceable to Cryogenic Radiometer803 in Fig.7.

. I ^resp (A)

Resultantly, the derived spectral responsivity of FCIS based-LEMCS Rpcis ⁼ p _c w r _esp ^

320 is fully traceable to primary level standards. R _FCIS 320 is the spectral response of the First Photodiodel20 in FCISlOO of FCIS based-LEMCSlll. The Second Photodiodel29 of FCISlOO of FCIS based-LEMCSlll, which is mainly used for measuring the time related measurements, and which sees Port_1101 in directly opposite position, is also used for coinciding the input laser beams on the same optical axis with respect to the Small Pin Holel09 at the center of Small Steel HemispherellO settled on Port_3103 axis in different measurements. With this type of configuration of the Second Photodiodel29 in the invention, in addition to time related measurements in the calculations of PE _av and PEa _y ^f - ^clem , the highly repetitive measurements in the determination of spectral responsivity R _FCIS 320, and the average photocurrents I _av 300 and I _a - ^clem 842 related to the averaged pulse energies PE _av 840 and PE^ ^{f clem} 845 are obtained because the input laser beams are collided on the Small Pin Holel09 at the center of Small Steel HemispherellO by tracking and maximizing the signal of the Second Photodiode on the Oscilloscopel30 screen for Gaussian Laser Beams501/601 of Pulsed Type Laser Source500, Chopped Type Laser Source600, and CW Laser Source800. The Second Photodiodel29 in the determination of the spectral responsivity R _FCIS 320 of FCIS based-LEMCS is only engaged for identical optical alignment of CW Laser Source800 towards inside of FCIS on the same optical beam path as in Fig.8. The details of determining the spectral responsivity Rp _CIS 320 of FCIS based- LEMCS are given in the following in item by item manner for easy understanding the process. In the numbering showing the steps to be applied, "a" shows that this measurement series belongs to "a-) Determination of the spectral responsivity Rpcis of FCIS based-LEMCS" and numbers as 1, 2, and etc. shows the sequence number of the steps being applied. a-1) First, CW Laser Source800 lasing at wavelength λ (nm) given in Fig.8 is run with a rated power of 10 mW and the CW Gaussian laser beam799 of CW Laser Source800 is oriented to Port_l of FCIS of FCIS based-LEMCS. The output powers of CW Laser Sources800 are reduced to a few mW level by using neutral density filters to guarantee eye safety together with eye protection equipments in optical alignment, the optical densities of which extends to 2.5, which are located in front of the collimators at z=0.

a-2) By using an IR viewer card having a compatible spectral range with that of CW Laser Source800, the CW Gaussian Laser Beam799 of CW Laser Source800 is centered on Port_l. The compatibilities and the relationships among the beam waists, the size of Port_1101, and the size of Small Steel Hemisphere, emphasized in "Details of FCIS" subsection of "DESCRIPTION" section, is taken into account in this step.

a-3) The centered CW Gaussian Laser Beam799 of CW Laser Source800 at Port_1101 is fallen onto the Small Steel Hemisphere on Port_3 by adjusting the Alignment Combination in Fig.8.

a-4) As soon as the CW Gaussian Laser Beam799 entering from Port_l 101 is fallen on the Small Steel HemispherellO, the inner diameter of which is 13 mm shown as in Fig.3, the Second Photodiodel29 assembled with the Small Steel HemispherellO on Port_3103 starts to detect the optical flux launched into the core of Zr ferrulel40 of HMS connectorl32 of the First MM Optical Fiber Patch Cordl50 through Small Pin Holel09 due to inner curvature structure of Small Steel HemispherellO.

a-5) The hemisphere structure of the Small Steel HemispherellO in the invention enables the CW Gaussian Laser Beam799 being captured by a 0.25 rad numerical aperture of the core of Zr ferrulel40 of HMS connectorl32 of the First MM Optical Fiber Patch Cordl50. a-6) The photocurrent generated by the Second Photodiodel29, transformed into voltage by means of Fast Response Current to Voltage Converterl27 in Fig.8 and the output voltage of Fast Response Current to Voltage Converterl27 is maximized in real time by adjusting the Alignment Combination in Fig.8. The maximum output voltage is obtained when the maximum irradiance level of CW Gaussian laser beam799 of CW Laser Source800 is coincided with Small Pin Holel09 of 0.1 mm detailed in Fig.4.

a-7) With this process described in this invention, the measurement reproducibility for the different measurements is enhanced because the crest corresponding to the maximum irradiance level of CW Gaussian Laser Beam799 of CW Laser Source800 entering from Port_l is targeted on the same point defined by the Small Pin Holel09 of 0.1 mm, back of which 62.5 μηι diameter core the core of Zr ferrulel40 of HMS type connectorl32 of the First MM Optical Fiber Patch Cordl50 is rest / placed, by maximizing the output voltage of Fast Response Current to Voltage Converterl27 combined to the Second Photodiodel29 on Port_3 on the screen of the Oscilloscopel30 in real time.

a-8) In the condition of the maximum output voltage of Fast Response Current to Voltage Converterl27, which corresponds to the Second Photodiodel29 detects the crest of the CW Gaussian Laser Beam799 of CW Laser Source800, the photocurrent I ^res P(A)200 generated by the First Photodiodel20 is read out proportional to the power P ^cw - ^res P( )201 of CW Laser Source800 lasing at wavelength λ (nm) by means of Electrometerll9.

a-9) After obtaining the photocurrent I ^res P(A)200 generated by the First Photodiode, the same CW Gaussian Laser Beam799 of CW Laser Source800 is applied to Optical Power Transfer Standard809 by substituting Optical Power Transfer Standard809 for FCIS based-LEMCS. With this application, the optical power P ^cw - ^res P( )201 of CW Laser Source800 for wavelength λ (nm) is obtained from Optical Power Transfer Standard809, traceable to CR803, in W.

a-10) These steps are repeated for the remaining of CW Laser Source800 and the spectral responsivities of FCISIOO of FCIS based-LEMCS are calculated by proportioning I ^res P (A)200 to pcw_resp 201 as R^ _CIS (A/W)320 to be used in the calculations of PE _av 840 and PE™ ^f - ^dem 845 in according to Eq.(16). In this invention, four CW Laser Sources800 are used, but any change in the number, wavelength, spectral bandwidth, and similar characteristics of lasers used in the invention doesn't change the philosophy of the invention. Different lasers can be used. a-11) The results of spectral responsivity R^ _CIS (A/W)320 of FCISIOO of FCIS based-LEMCSlll described in this invention together with the related partial uncertainties are given below; R 980

FCIS .80X10- ⁵ φ ; u(R¾»s) I at 980.0 nm

1064

FCIS 20x10- (£) _{! U} (Rgg) at 1064.0 nm

1309

FCIS 45x10- ( ) _{; u} (Rgg>) at 1309.0 nm

1549

FCIS 07x10- (A) ; u(Rg?) at 1549.0 nm Any change in these results introduced here doesn't change the philosophy of the invention because the FCIS based-LEMCS is an preferred embodiment. These spectral responsivities Rpcis (A/W)320 are used in the calculations of the averaged pulse energies PE _av 840 and PE^ ^clem 845 of Pulsed Type Laser Source, and Chopped Type Laser Source, generating infinite pulse train in time domain, the wavelengths of which are conform to these wavelengths 980.0 nm, 1064.0 nm, 1309.0 nm, and 1549.0 nm, according to Eq.(16). Typical relative standard (combined) uncertainty is calculated as 0.80% (k=l) from the measurement series related to the determination of the spectral responsivity R _FCIS (A/W)320 of FCISIOO of FCIS based-LEMCSlll, which includes the all the uncertainty components coming from the calibrations of the transfer standards calibrated against these primary level standards in Fig.7 as well as the individual uncertainties of the primary level standards in Fig.7.

b-) Method of measuring the averaged pulse energy PE _av of a Pulsed Type Laser Source by means of FCIS based-LEMCS; After completion of determination the spectral responsivities Rpcis (A/W)320 of FCISIOO of FCIS based-LEMCSlll performed according to the sequential steps specified in the above section of "Determination of the spectral responsivity Rpcis °f FCIS based-LEMCS", the main configuration depicted in Fig.l is considered, which is the main configuration of this invention to measure the averaged pulse energy of a Pulsed Type Laser Source500 as a function of the repetition frequency f _av 331. In order to measure the averaged pulse energy of Pulsed Type Laser Source by using FCIS based-LEMCS, Pulsed Type Laser Source500 instead of Chopped type Laser Source600 depicted in Fig.2 is placed opposite Port_1101 of FCISIOO of FCIS based-LEMCSlll. According to Eq.(16), the pulse energy related parameters of Rp _CIS 320, T _av 330, f _av 331 and I _av 300 should be measured. Rp _CIS 320 is determined by the sequential steps given in the section of "Determination of the spectral responsivity Rpcis °f FCIS based-LEMCS". The remaining parameters of the averaged pulse energy PE _av (J)840 in Eq.(16), which are I _av 300, f _av 331, f _av 331, I _av 300, are directly measured by FCIS based-LEMCS designed in this invention and the operation steps to measure these parameters of the Pulsed Type Laser Source are introduced as the sequential operation steps at the following. In the measurement of the averaged pulse energy PE _av (J)840 of Pulsed Type Laser Source500: - If the spectra of Pulsed Type Laser Source500, the averaged pulse energy PE _av 840 of which is to be measured by FCIS based-LEMCSlll, is different from R _FCIS 320 determined by the steps stated in the section of "Determination of the spectral responsivity Rpcis of FCIS based-LEMCS", a suitable fitting programs to make interpolation is engaged by taking the spectral responsivity Rp _CIS 320 of the First Photodiodel20 mounted to FCISIOO into account.

- The First Photodiodel20 mounted on Port_2102 of FCIS based-LEMCSlll is used for measuring I _av 300, corresponding to P _av 301 of the pulsed type laser source.

- The Second Photodiodel29 assembled with Small Steel HemispherellO and mounted on Port_3103 of FCIS based-LEMCSlll is used for measuring the averaged repetition period T _av 330, the averaged repetition frequency f _av 331, and number of pulses N of Pulsed Type Laser Source500, which is considered in a burst type laser source, and it is N=l for infinite pulse train having constant repetition period T(s)320. In this invention N=l for Pulsed Type Laser Source500 producing infinite laser pulse train in time domain.

- The Second Photodiodel29 assembled with Small Steel HemispherellO and mounted on Port_3103 of FCIS of FCIS based-LEMCS, in addition to time/frequency related measurements, is also used for alignment of Pulsed Gaussian Laser Beam501 of Pulsed Type Laser Source500 entering from Port_1101 is targeted on the same point defined by the Small Pin Holel09 of 0.1 mm, back of which 62.5 μηι diameter core of Zr ferrulel40 of HMS connectorl32 of the First MM Optical Fiber Patch Cordl50 is located, by maximizing the output voltage of Fast Response Current to Voltage Converterl27 combined to the Second Photodiodel29 on Port_3103 on the screen of the Oscilloscopel30 in real time.

In the numbering showing the steps to be applied, "b" shows that this measurement series belongs to the section of "b-) Method of measuring the averaged pulse energy PE _av of a Pulsed Type Laser Source by means of FCIS based-LEMCS" and numbers as 1, 2, and etc. shows the sequence number of the steps being applied.

b-1) First, Chopped Type Laser Source600, which is a part of FCIS based-LEMCS invented, is removed from FCIS based-LEMCS illustrated in Fig.2 and Pulsed Type

Laser Source500, the averaged pulse energy PE _av 840 of which is to be measured according to Eq.(16), is placed opposite Port_1101 of FCISIOO of FCIS based- LEMCSlll as in Fig.l b-2) Pulsed Type Laser Source500 lasing at wavelength λ (nm) given in Fig.l is run and the Pulsed Gaussian Laser Beam501 of Pulsed Type Laser Source500 is oriented to Port_1101 of FCISIOO of FCIS based-LEMCSlll as in Fig.l.

b-3) The output peak power levels P ₀ 400 of Pulsed Type Laser Source500 are reduced to a few mW level in order to guarantee eye safety together with eye protection equipments by using one of the suitable one of the neutral density filters, the optical densities of which extends to 2.5, which are located in front of the collimators at z=0.

b-4) By using an IR viewer card having a compatible spectral range with that of Pulsed Type Laser Source, the peak power levels P ₀ 400 of the Pulsed Gaussian

Laser Beams501 of Pulsed Type Laser Source500 is reduced by a suitable neutral density filter, and the Pulsed Gaussian Laser Beams501 are centered on Port_l by means of Alignment Combinationl62 in Fig.l. The compatibilities and the relationships among the beam waists, the size of Port_l, and the size of Small Steel Hemisphere, emphasized in "Details of FCIS" subsection of

"DESCRIPTION" section, should be taken into account in this step.

b-5) As soon as the Pulsed Gaussian Laser Beam501 of Pulsed Type Laser Source500 entering from Port_1101 is fallen on the Small Steel HemispherellO, the inner diameter of which is 13 mm shown as in Fig.4, the Second Photodiodel29 assembled with the Small Steel HemispherellO on Port_3103 starts detecting the optical flux entering from Port_1101.

b-6) The maximization of the voltage output of Fast Response Current to Voltage Converterl27 combined to the Second Photodiodel29 assembled with the Small Steel HemispherellO on Port_3 which starts to detect the Pulsed Gaussian Laser Beam501 entering from Port_1101 is performed by means of Alignment Combinationl62 and by tracking the screen of the Oscilloscopel30 in real time. With this process in the invention, the measurement reproducibility for individual and independent pulse energy measurements is enhanced because the crest corresponding to the maximum irradiance level (crest) of Pulsed Gaussian Laser Beam501 entering from Port_1101 is targeted on the same point defined by the Small Pin Holel09 having a diameter of 0.1 mm, back of which 62.5 μηι diameter core of Zr ferrulel40 of HMS connectorl32 of the First MM Optical Fiber Patch Cordl50 is rest/located. The amplitude of the maximization voltage on the screen of the Oscilloscopel30 is not important. What is important at this point is to obtain maximum voltage and maximum voltage is obtained when the crest of the maximum irradiance level of the Pulsed Gaussian Laser Beam501 of Pulsed Type Laser Source500 entering from Port_1101 collides on the center of the Small Pin Holel09 having a diameter of 0.1 mm, back of which 62.5 μηι diameter core of Zr ferrulel40 of HMS connectorl32 of the First MM Optical Fiber Patch Cordl50 is rest/located.

b-7) After completion of the maximization process, the output pulse power P ₀ 400 of Pulsed Type Laser Source500 is adjusted to its normal operation power level to be measured and the Second Photodiodel29 assembled with Small Steel HemispherellO on Port_3103 of FCISIOO of FCIS based-LEMCSlll starts to be directly used for time/frequency related measurements, which are the averaged repetition frequency f _av (Hz)331, the averaged repetition period T _av (s)330, the averaged pulse width PW _av (s) 342, the averaged dead time DT _av (s)340, and the averaged Duty Cycle _av 299 which is normalized to 1. b-8) The pulsed voltage signal at the output of Fast Response Current to Voltage Converterl27 connecting to the Second Photodiodel29 through Mechanical Attenuatorl70 on Port_3103, caused by Pulsed Type Laser Source500 operating in its normal operation power level, is observed on the screen of the Oscilloscopel30. b-9) The time/frequency related parameters of the Pulsed Gaussian Laser Beams501 of Pulsed Type Laser Source500, the averaged pulse energy PE _av 840 in Eq.(16) of which is aimed to be measured, are directly measured and averaged in real time without the effect of time constant τ of FCISIOO of FCIS based- LEMCS111 and the effect of of the pulse response ζ ^{ρ 1} of the First Photodiode 120 by Time Interval Counterl35 in Fig.l, which is traceable to ¹³³ Cs (or ⁸⁷ Rb) Atomic Frequency Standard in Fig.7, to which Fast Response Current to Voltage Converterl27 and the Second Photodiodel29, are consecutively connected in this invention. The averaged repetition period T _av (s) 330, and the averaged repetition frequency f _av (Hz) 331 obtained from this measurement are the same parameters as those in Eq.(16). b-10) During the measurement of the averaged repetition frequency f _av (Hz) 331 and the averaged repetition period T _av (s)330 of Pulsed Type Laser Source500, the First Photodiodel20 measures the average photocurrent I _av (A)300 in Fig.l and Fig.3, proportional to the average optical p ower l av (W) 301 in Fig.3, simultaneously as an advantage of this invention. b-11) The resultant and averaged pulse energy PE _av (fav)840 in Eq.(16), as a function of the averaged repetition frequency f _av 331, is calculated with the data series, I _av (A)300 obtained from "b-11", the repetition p erioQ 1 _a v (s) 330 obtained from "b-10", by considering Hz from the equivalent circuitl71 of the First Photodiodel20 in Fig.3 and RF _CIS 320 obtained from the section of ^" a-) Determination of the spectral responsivity Rpcis °f FCIS based-LEMCS". b-12) The maximum PW, PW™ ^ax < 1.9xl0 ⁴ s corresponding to PE™ ^ax =100 mj pulse energy for a maximum peak power P ₀ ^max =522 W, which matches the peak power level P ₀ 400 of Pulsed Type Laser Source500 in Fig.2 which can be detected by the First Photodiodel20 without saturation.

The ultimate limit parameters of Pulsed Type Laser Source500 to be measured by FCIS based-LEMCSlll for the maximum peak laser power of P ₀ ^max =522 W in the invention are, *minimum pulse width, PW™ =. 0.736 μ5, corresponding to PE _av 840 of 384 μ] obtained from the pulse response characteristic ζ ^{ρ 1} of the First Photodiodel20, and

*minimum dead time, DT™ ⁿ =1.7 μ≤ from the necessary time of sufficient heat dissipation inside the Small Steel HemispherellO as a target, which produces the minimum averaged repetition period of T™ ⁿ of 2.436 μ5, corresponding to a maximum averaged repetition frequency f™ ^ax of 410509 Hz.

In the measurement of the averaged pulse energy of Pulsed Type Laser Source500 lasing properly to the infinite pulse wave train given in Fig.3 by means of FCIS based- LEMCSlll, the compatibility of the beam sizes with Port_1101 and Port_3103 of FCISIOO of FCIS based-LEMCSlll, and the permissible maximum energy level to be applied to FCIS based-LEMCSlll should be taken into account and the calculations and approaches given in this invention should be regarded. Pulse energies of Pulsed Type Laser Source500 operating in burst mode can be measured by FCIS based-LEMCSlll by applying the suitable integrating/averaging time settings of Electrometerll9 in Fig.l.

In this section a brief uncertainty evaluation for FCIS based-LEMCS in this invention are introduced. This uncertainty analysis covers a pulse energy PE _av 840 of 40 μ] and pulse energy PE _av 840 of 100 mj for a Pulsed Type Laser Source500 lasing at 1549.0 nm (f _av =500 Hz, Duty Cycle=0.5) and 1064.0 nm (f _AV =5 Hz, Duty Cycle=0.83) respectively. For both averaged repetition frequencies f _av 331 are very very smaller than ί¾ΐΒ ⁼ 995222 Hz and the frequency response term of Eq.(16), 1/ (1 + f ^aV /r _f >d ₁ y /ι yields 1, so this term is not included in the uncertainty model function.

/ f-3dB

The partial uncertainties of the uncertainty budgets given in Fig.9a and Fig.9b are u(I _av )351, u(f _av )352, U(RFCIS)353. These partial uncertainties includes the standard (combined) uncertainties coming from the traceable calibrations of Electrometerll9, Time Interval Counterl35 to primary level standards shown in Fig.7, and the spectral responsivity determination Rpcis 320 of FCISIOO of FCIS based-LEMCSlll against Optical Power Transfer Standard809 shown in Fig.7 and Fig.8. The inclusion of these standard uncertainties coming from the individual calibration of Electrometerll9, Time Interval Counterl35, and Rpcis 320 in the individual and relevant partial uncertainty value, designated as u(I _av )351, u(f _av )352, U(RFCIS)353, is executed as root of summing of the squared values of the standards uncertainties. The largest uncertainty portion in both u(I _av )351, and u(f _av )352 is composed of the standard deviations during the measurement of the average photocurrent I _av 300 generated by the First Photodiodel20 in Eq.(16), and the measurement of the averaged repetition frequency f _av (Hz)331 (or repetition period T _av (s)330), which have normal type distribution functions (multiplier = 1). Because U(RFCIS)353 is a predefined value obtained from the determination of R _CIS 320 described in the section of "a-) Determination of the spectral responsivity Rp _CIS of FCIS based-LEMCS", it is included in both of the uncertainty budgets as rectangular type distribution function (multiplier = 1/V3). Regarding u(Ore _P ro)354, which is named as the partial uncertainty in the error Ore _P ro329 in the measurement reproducibility of the averaged pulse energy of the pulsed type laser source; the error Ore _P ro329 in the measurement reproducibility is zero for perfect reproducibility in the uncertainty calculation. The partial uncertainty u(Ore _P ro) 354 in the error Orepro329 of the measurement reproducibility of the averaged pulse energy PE _av 840 is calculated by using the standard deviations of the averaged pulse energy PE _av 840 values obtained from the successive positioning processes of FCISIOO of FCIS based-LEMCSlll opposed to the collimator of the Pulsed Type Laser Source at z=0.

c-) Calibration of a Commercial Laser Energy Meter by using Chopped Type Laser Source in FCIS based-LEMS;

In the numbering showing the steps to be applied, "c" shows that this measurement series belongs to the section of "c-) Calibration of a Commercial Laser Energy Meter by using Chopped Type Laser Source in FCIS based-LEMS" and numbers as 1, 2, and etc. shows the sequence number steps being applied. Superscript "_clem" shows the relevant parameter in the calibration of Commercial Laser Energy Meter999.

c-1) The complete setup demonstrated in Fig.2, called as FCIS based-LEMCSlll, is configured for traceable calibration of Commercial Laser Energy Meter999 by using Chopped Gaussian Laser Beams601 of Chopped Type Laser Source600, which are generated by means of the combination of DC Motor599 with a series chopper901-909 from CW Gaussian Laser Beam799 of CW Laser Source800, called four DFB lasers.

c-2) Depending on the measurement range of Commercial Laser Energy Meter999, the selections of the relevant chopper having a individual Duty

Cycle322, repetition frequency f (Hz) 322, and the peak power P ₀ 400 of Chopped Type Laser Source600 according to the Eq.(16). c-3) CW Laser Source800 lasing at wavelength λ (nm) given in Fig.2 is run and the CW Gaussian Laser Beam799 of CW Laser Source800 is oriented to PortJ.101 of FCISIOO of FCIS based-LEMCSlll when DC Motor599 is not activated and so the chopper901-909 doesn't rotate.

c-4) The output powers of CW Gaussian Laser Beam799 of CW Laser Sources800 in Fig.2 is reduced to a few mW level in order to guarantee eye safety together with eye protection equipments by using one of the suitable one of the neutral density filters, the optical densities of which extends to 2.5, which are located in front of the collimators of Single Mode Optical Fiber Patch Cord876 at z=0.

c-5) By using an IR viewer card having a compatible spectral range with that of CW Laser Source800, the CW Gaussian Laser Beam799 still at the output of the chopper901-909 in continuous regime, the power of which is reduced by means of a suitable neutral density filter, is centered on Port_1101 of FCISIOO of FCIS based-LEMCSlll by means of Alignment Combinationl62 in Fig.2. The compatibilities and the relationships among the beam waists, the size of Port_1101, and the size of Small Steel HemispherellO, emphasized in "Details of

FCIS" subsection of "Description" section, is taken into account in this step.

c-6) As soon as the CW Gaussian Laser Beam799 entering from the center point of Port _. llOl of FCISIOO of FCIS based-LEMCSlll is fallen on the Small Steel HemispherellO, the circular diameter of which is 13 mm shown as in Fig.4, the Second Photodiodel29 assembled with the Small Steel HemispherellO on

Port_3103 of FCISIOO of FCIS based-LEMCSlll starts detecting the optical flux entering from Port_1101. At this step, DC Motor599 is not activated and the chopper901-909 doesn't rotate yet.

c-7) When the chopper901-909 doesn't rotate yet, and the maximization of the voltage output of Fast Response Current to Voltage Converterl27 combined to the Second Photodiodel29 assembled with the Small Steel HemispherellO on Port_3103 of FCISIOO of FCIS based-LEMCSlll starting to detect the CW Gaussian Laser Beam799 entering from Port_1101 of FCISIOO of FCIS based- LEMCSlll is performed by means Alignment Combinationl62 and by tracking the screen of the Oscilloscopel30 in real time. With this process in the invention, the measurement reproducibility for individual and independent pulse energy measurement is enhanced because the crest of CW Gaussian Laser Beam799 corresponding to the maximum irradiance level entering from Port_1101 is targeted on the same point defined by the Small Pin HolellO of 0.1 mm, back of which 62.5 μηι diameter core of Zr ferrulel40 of HMS connectorl32 of the First

MM Optical Fiber Patch Cordl50 is rest/located. The amplitude of the maximization voltage on the screen of the Oscilloscopel30 is not important. What is important at this point is to obtain maximum voltage and maximum voltage is obtained when the crest of the maximum irradiance level of the CW Gaussian Laser Beam799 entering from Port_1101 collides on the center of Small

Pin Holel09 of 0.1 mm, detailed in Fig.5.

c-8) After completion of the maximization process, DC Motor599 in Fig.2 is activated and the chopper901-909 begins to rotate, and Chopped Type Laser Source600 of FCIS based-LEMCMlll and Chopped Gaussian Laser Beams601 are available now. With beginning the rotation of the chopper901-909, the

Second Photodiodel29 assembled with Small Steel HemispherellO on Port_3103 of FCIS based-LEMCSlll starts to be directly used for time/frequency related measurements, the averaged repetition frequency (Hz)843, the averaged repetition period T^ ^clem (s)844, and the Duty Cycle, normalized to 1. The combination of CW Laser Source800 with the chopper901-909 in the invention provides the nine different Duty Cycles varying from 0.17 to 0.83 at any repetition frequency f (Hz)321 extending from 5 Hz to 2 kHz in the calibration processes of Commercial Laser Energy Meters999 by means of FCIS based- LEMCS111, traceable to primary level standards given in Fig.7. c-9) The voltage signal generated by the Second Photodiodel29 assembled with the Small Steel HemispherellO on Port_3103 of FCISIOO of FCIS based-

LEMCS111 is chopped instead of CW Gaussian Laser Beam799 and Chopped Gaussian Laser Beams601 generated by Chopped Type Laser Source600 of FCIS based-LEMCMlll are observed on the screen of the Oscilloscopel30. c-10) The time/frequency related parameters of Chopped Gaussian Laser Beams601 of Chopped Type Laser Source600, the reference and averaged pulse energy PEa _y ^f - ^clem 845 of which is aimed to be measured, are directly measured and averaged, in real time, without the effect of time constant τ of FCISIOO of FCIS based-LEMCSlll and the effect of the pulse response ζ ^{ρ 1} of the First Photodiode 120 by Time Interval Counterl35 in Fig.2, which is traceably calibrated to ¹³³ Cs (or ⁸⁷ Rb) Atomic Frequency Standard804 in Fig.7, to which the Fast Response Current to Voltage Converter and the Second Photodiodel29 is consecutively connected in the invention. The repetition period _T ref clem ^ _{g44 and the repetition} frequency fav ^dem (Hz) 843 obtained from this measurement are the same parameters as those in Eq.(16). c-11) During the measurement of the averaged repetition frequency f ^ ^dem

(Hz)843 and the averaged repetition period T _ay ^{f clem} (s)844 of the chopped Gaussian laser beams, the First Photodiodel20 measures the average photocurrent I^ ^clem (A) 842 in Fig.2, proportional to the average and reference pulse energy PE^ ^clem 845 in Fig.2. The pulse energy is called as "the reference" because it will be measured by FCIS based-LEMCSlll and then the same pulse energy level ΡΕ^ ^{Γ clem} 845 will be applied to Commercial Laser Energy Meter999 by substitution. c-12) The resultant and the averaged and reference pulse energy _pE ref ciem ^ref ciem-j _{g45 in Eq} ( ₂₈ ) as a function of the averaged repetition frequency f™ ^f - ^dem (Hz)843, is calculated with the data series, I™ ^f - ^Clem (A) 842 obtained from "c-11", the averaged repetition period ^clem (s) obtained from "c-10", by considering Hz from the equivalent circuitl71 of the First Photodiodel20 in Fig.3 and Rf is 320 obtained from the section of ^" a-) Determination of the spectral responsivity Rpcis of FCIS based- LEMCS".

i ref_clem

'av

f ref_clem _{M Ό} Χ

rav ^{i K} FCIS

(28)

Eq.(28), which is written for Chopped Type Laser Source600, is the same as Eq.(16), which is written for the calculation of the averaged pulse energy of Pulsed Type Laser Source. The calculated pulse energy ΡΕ^ ^{Γ clem} (f _a v) 845 by means of FCIS based-LEMCSlll in unit of (J) will be the reference pulse energy

PE _a ^clem (f _av ) 845 for Commercial Laser Energy Meters999 to be calibrated, which is determined fully traceably to primary level standards demonstrated in Fig.7.

c-13) The sensitive surface of Commercial Laser Energy Meter999 shown as in Fig.2, which is Input Port839, is directly and perpendicularly placed against the propagation way of the Chopped Gaussian Laser Beam601, the averaged and reference pulse energy PE _a y ^{f clem} (f _av ) 845 of which is determined from the steps specified from "c-1" to "c-12", which is called the reference averaged pulse energy. The readout of Commercial Laser Energy Meter999 is recorded as PE ^clem 841 in unit of J.

c-14) The linear calibration factor is calculated as,

Y(^ fa ^r v ^{f dem} ) = Pa ^r v ^{f clem} (fav)/PE ^clem (fav)< which is traceable to primary standards, in units of W, A, and s. γ(λ, is the linear calibration factor for Commercial Laser Energy Meter999.

FCIS based-LEMCSlll together with the calculations, the calibration method of Commercial Laser Energy Meter999 and averaged pulse energy measurement method, all of which are traceable to primary level standards shown in Fig.7 herein, is a preferred embodiment.