Label for authentication of a product

The present invention relates to a label for authentication of a product.

The issues of authentication and counterfeit deterrence can be important in many contexts. Bills of currency, stock and bond certificates, pharmaceuticals, luxury goods, credit cards, passports, bills of lading, as well as many other legal documents (e.g., deeds, wills, etc.) all must be reliably authentic to be useful. Authentication and avoidance of counterfeiting can also be important in many less obvious contexts. For example, improved verification/counterfeiting prevention mechanisms would be very useful in, for example, verifying the contents of shipping containers, quickly identifying products with particular health or criminal histories, etc. Counterfeit products are, by definition, unauthorized copies of a product, its packaging, labeling, and/or its logo(s). Attractive targets for counterfeiters are items with significant brand equity or symbolic value, where the cost of production is below the market value.

Authentication is the act of confirming the truth of an attribute of a piece of data claimed true by an entity so as to verify if an object, for example a luxury good, is authentic. In contrast with identification, which refers to the act of stating or otherwise indicating a claim purportedly attesting to a person or thing's identity, authentication is the process of actually confirming that identity. It might involve confirming the identity of a person by validating their identity documents, verifying the authenticity of a website with a digital certificate, or ensuring that a product is what its packaging and labeling claim to be. In other words, authentication often involves verifying the validity of at least one form of identification.

Counterfeiting has reached epidemic proportions worldwide, especially in the area of con sumer goods including goods made from fabric, plastic, leather, metal, or combinations thereof such as clothing, pharmaceuticals, luxury goods, watches, handbags and wallets, perfumes, and other consumer goods. Electronics and software products are also particular targets of counterfeiters, who appropriate the value of trademarks or copyrights without license. Since costs savings based on decreased incremental cost of production (exclusive of license fees) is not a necessary element in the counterfeiting scheme, the counterfeit articles may be of apparently high quality and closely resemble authentic articles. Indeed, counterfeit articles can so closely resemble genuine goods that consumers readily confuse the counterfeit articles with the authentic articles. In other circumstances, the manufacturer segments the world market for different sales and distribution practices, so that the“coun- terfeit” goods may be essentially identical to authorized goods. Further, in many instances, a manufacturer produces goods under license from an intellectual property owner, and thus sales outside the terms of the license agreement are also“counterfeit”.

There are many methods of preventing counterfeiting and deterring fraudulent producers of goods. Some attempts have included putting encoded or unencoded markings directly on the goods themselves (analogous to an artist's signature on his or her painting). The problem with this methodology is that as soon as the counterfeiter learns to emulate the“signa ture”, the technique becomes defunct and worthless for authentication purposes.

For example, in the realm of currency, anti-counterfeiting methods have become quite so phisticated— the use of two-dimensional authentication mechanisms such as watermarks or special threads incorporated within the paper itself are helpful. However, they remain vulnerable to reverse-engineering. Once a potential counterfeiter learns how to emulate the anti-counterfeiting technology, he may use it to his own advantage. Therefore, the simple release of anti-counterfeiting technology into the world can be an indirect pathway to advance the state of criminal technology.

On the other hand, there exists a great need for the end-user to authenticate the product by himself without using expensive and complex tools, such as interferometers. However, every feature that can be observed with the bare eye can easily be reproduced while small and complex features need special tools for their read out.

Thus, there remains a great need for labels that are both, secure and accessible by the end-user. In more detail, there remains a need for fabricating highly encrypted patterns, which can be used to authenticate associated objects, as well as an ability to quickly and accurately verify these objects for authenticity. Further, there remains a need that the encrypted pattern should be hardly forgeable and unique. In other words, a great need exists to demarcate the means for the cheap and relatively simple reproduction of these highly technical encrypted patterns, so that criminals would be discouraged from, essentially, counterfeiting the label described herein.

Further, there remains a need for economically fabricating labels that are unforgeable, unique and easy to read-out by nearly anybody and nearly anywhere.

This object is solved by the subject matter of the independent claim. Advantageous embodiments of the present invention are the subject matter of the dependent claims. According to an embodiment, a label for authentication of a product comprises a light emitting unit for generating a shaped light beam so as to identify the label.

Additionally, the label according to the embodiment comprises a power supply unit for supplying power to the light emitting unit; wherein the power supply unit comprises a receiving device for extracting the power from a time-varying electromagnetic field.

The light emitting unit enables actively emitting a light pattern, which is detectable with the bare eye or an optical detecting device, advantageously an optical detecting unit of a smartphone such as a camera. In more detail, the light pattern is generated by actively powering the light emitting unit with external power, which is supplied to the light emitting unit. Consequently, the light pattern is detectable without having the need of additional optical elements, such as an additional light source or an additional optical filter. In other words, the complexity for detecting the light pattern is reduced. According to an example of the prior art, when using a passive powered light emitting unit, for example a fluorescing light pattern, the substance has to absorb light or other electromagnetic radiation. More specifically, the absorbed light has preferably a shorter wavelength, and therefore a higher energy.

According to the present invention, according to which the light emitting unit is powered with a power supplying unit, the need for additional light source for powering the light emitting unit is unnecessary. Further, by avoiding the additional light source, the use of filters to distinguish between light emitted by the additional light source and light emitted by the light emitting unit is obsolete.

Advantageously, according to a first embodiment, the light emitting unit comprises a light emitting diode for generating light and a transparent layer comprising a plurality of particles for shaping the light generated by the diode.

Additionally or alternatively, according to a second embodiment, the light emitting unit comprises a substrate; an aperture layer with a plurality of openings, wherein each opening extends through said aperture layer from a bottom surface of the aperture layer to an opposing top surface of the aperture layer; and a plurality of light sources. Each individual light source of the plurality of light sources comprises a core element extending from a top surface of the substrate through one of the plurality of openings formed in the aperture layer. Furthermore, each individual light source comprises a shell element extending on and/or around the core element of the respective individual light source. Furthermore, the shell element of each individual light source is spaced apart from the substrate.

Consequently, according to the first and second embodiment light is influenced by a plurali ty of particles or the light is emitted by a plurality of light sources. In both cases, a unique light pattern is emitted. In more detail, according to the first embodiment the particles are spatially distributed in the transparent layer. Alternatively, according to the second embodiment the light sources are spatially distributed in and/or on top of the label. Thus, in both cases, by analyzing the geometric arrangement of the emitted light pattern, the label can be used for authenticating a product. Advantageously, according to the second embodi ment a plurality of thousand to a hundred thousand light sources are arranged on an area of 1 mm ² . Consequently, a particularly unique pattern can be generated.

Further, according to the first and second embodiment, the light sources are semiconduc tor light sources. In more detail, according to the second embodiment each light source comprises a core element contacting a substrate and a shell element extending on and/or around from the core element. In other words, according to the first and the second embodiment each light sources is a semiconductor light source that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. This effect is also called electroluminescence. The choice of the material for the core and shell material or the diode usually depends on the desired light source properties. In principle, all material combinations, well known from solid-state light source gain material, in particular direct bandgap semiconductors, can be applied to the light source core/shell structures, as well. Advantageously, according to the second embodiment, each light source further comprises a pn junction or a pin junction. Hence, the invention allows to directly integrating the diode into the core shell structure.

In an example of the first embodiment, the plurality of particles at least partly absorb a part the light emitted by the diode, and thus, the beam is shaped and the unique pattern is outputted by the label.

According to an advantageous aspect of the first embodiment, the light emitting diode is a vertical-cavity surface-emitting laser, VCSEL. Thus, a particularly bright and directed light source, which can be easily detected, is generated.

According to a further advantageous aspect of the first embodiment, the transparent layer comprises Si02, epoxy, glue, or a polymer. Such materials a particular easy fabrication of the layer carrying the particles is enabled. Furthermore, these materials are particularly economic. Moreover, such layer materials are advantageous to uniquely arrange the particles. In more detail, for example in case of a glue, glue outgases during the curing process, and thus, the transparent layer shrinks. Consequently, the relative distance between the particles in the glue changes. Thus, it becomes more severe to reproduce the specific arrangement of the particles in the layer, as the curing process has to be foreseen.

According to a further advantageous aspect of the first embodiment, the particles are at least partly reflecting the generated light. According to one aspect, the particles are made of metal, e.g. cupper, a dielectric, a phosphorescence, or a non-linear absorber. Consequently, the particles shape the beam not only by absorption, i.e. generating a shadow, but additionally shape the light by the reflection pattern.

According to an even more advantageous aspect of the first embodiment, a VCSEL is combined with reflecting particles. As known to the person skilled in the art, the light of the laser is coherent. Thus, the light by the plurality of particles can interfere. As a conse quence, the interfering effect shapes the beam, and thus, the pattern becomes more complex.

According to a further advantageous aspect of the first embodiment, the transparent layer comprises a bottom surface facing the light emitting diode and an opposing top surface for outputting the shaped beam, and wherein a first particle is arranged closer to the top surface than a second particle. In other words, arranging the particles not only in two dimen sions, namely in a single plane normal to the light output direction of the VCSEL, makes the pattern more complex. In particular, the degree of freedom becomes larger, and thus, the pattern becomes more complex.

According to an even more advantageous aspect of the first embodiment, a VSCEL is combined with reflecting particles wherein a first particle is arranged closer to the top sur face than a second particle.

In an example of the second embodiment, a lower part of said core element and/or said shell element may comprise a first semiconductor region with a first doping concentration, said lower part facing said substrate, and an upper part of said core element and/or said shell element may comprise a second semiconductor region with a second doping concentration different from said first doping concentration, said upper part facing away from said substrate. In this configuration, a horizontal or lateral p-n junction may be formed. As an example of the second embodiment, said first doping concentration may be a p concentration, and said second doping concentration may be an n concentration, or vice versa. Said n concentration is preferably at least 5 times smaller than said p concentration. In an example, said n concentration is at most 20 times smaller than said p concentration.

Even more advantageously in the second embodiment, an intrinsic layer is formed between the core element and the shell element. Advantageously, the intrinsic layer may be a semiconductor material with a lower bandgap than the semiconductor material of the core element and a lower bandgap than the semiconductor material of the shell element. Even more advantageously, the intrinsic layer may form a quantum well structure. In particular, the quantum wells are formed by a semiconductor material with a lower bandgap, e.g. GaAs, sandwiched between two layers of semiconductor material with a wider bandgap, e.g. AIGaAs.

Further, the light emitting unit according to the second embodiment comprises an aperture layer with a plurality of openings. Each core element of the pluralities of light sources ex tends through one of said openings of the plurality of openings formed in the aperture lay er. Thus, the aperture layer enables to arrange the light sources emitting the unique light pattern.

Further, the shell element of the second embodiment is spaced apart from the substrate. Additionally, the core element is in contact with the substrate. Thus, each light source can be contacted by contacting the shell element with a first contact and the substrate with a second contact. Hence, an efficient contacting is possible. A shell element not spaced apart from the substrate can cause a short circuit between the shell element and the sub strate.

Further, according to the first embodiment and the second embodiment the power supply unit comprises a receiving device for extracting power from a time-varying electromagnetic field. Such a receiving device enables a wireless power transfer (WPT), wireless power transmission, wireless energy transmission (WET), or electromagnetic power transfer. Ac cording to the present application, wireless power transfer is the transmission of electrical energy without wires as a physical link. In a wireless power transmission system, a transmitter device, driven by electric power from a power source, generates a time-varying electromagnetic field, which transmits power across space to the receiver device, which ex tracts power from the field and supplies it to an electrical load, namely the light emitting unit. The technology of the wireless power transmission eliminates the use Of the wires and batteries, thus increasing the mobility, convenience, and safety of an electronic device for all users. Additionally, wireless power transfer to power the light emitting unit where inter connecting wires are inconvenient, hazardous, or are not possible.

According to an advantageous aspect of the second embodiment, the bottom surface of the aperture layer is facing the top surface of the substrate. Even more advantageously, the bottom surface of the aperture layer is contacting the top surface of the substrate. Hence, the light emitting unit can be fabricated in a compact layer structure and an economic fabrication is enabled. For example, well-known procedures to fabricate a layer structure, such as thermal oxidation or sputtering materials on a wafer, can be employed.

Additionally or alternatively, according to an advantageous aspect of the second embodiment, the aperture layer comprises a dielectric material, preferably SiC>2. Consequently, the aperture layer forms an isolator between the shell element, which is spaced apart from the substrate, and the substrate. This enables a particularly easy fabrication and enhances the contacting quality to supply power to the light emitting unit. In particular, the aperture layer itself prevents an electric contact between the shell element and the substrate.

Additionally or alternatively, according to an advantageous aspect of the second embodiment, the aperture layer has a thickness of less than 5 nm, and preferably between 1 nm and 2 nm. In other words, the aperture layer is a thin mask layer formed on the substrate swiftly and without sophisticated fabrication techniques.

Advantageously, according to an advantageous aspect of the second embodiment, the aperture layer can be etched easily by standard fabrication techniques, but is still sufficient to define the positions at which core elements of the light sources grow on the substrate with high precision, and to support the growth of the core elements in these positions. Before the etching step, the aperture layer can be provided by oxidation of the top few nanometers of semiconductor material exposed to air such as Si/SiC>2. Even more advanta geously, the aperture layer thickness can be increased before forming the openings by thermal oxidation or sputtering up to 100B nm. Thus, the openings can be easily formed by an etching process.

According to one advantageous aspect of the second embodiment, embodiment, the aperture layer comprises at least one recess extending from the top surface of the aperture layer. A recess is similar to a blind hole. It is a hole or recess that is etched to a specified depth without breaking through to the other side of the aperture layer. Advantageously, the top surface of the aperture layer has a plurality of recess so as to form a rough surface, preferably having a root mean square (rms) of 0.2 nm to 1 nm.

Additionally or alternatively, according to an advantageous aspect of the second embodiment, the top surface of the aperture layer comprising residues of an etching material, preferably HF and/or HN03, said residues of the etching material resulting from an etching process to produce a rough top surface. Thus, a random pattern is generated by an etching process, which enables to fabricate a pattern of openings that could be hardly forgeable and is particularly unique. Furthermore, such a pattern is easy to fabricate.

In more details, according to an advantageous aspect of the second embodiment, the etching of the aperture layer forms openings at random positions. A direct contact of the top surface of the aperture layer with the etching material, however, is different to standard fabrication techniques of semiconductor light sources. These processes generally use a masking process protecting the top surface of the aperture layer in order to generate light sources on well-defined positions. Here, the top surface is not protected with a mask, and thus, the aperture layer comprises openings at random positions.

Further, according to an advantageous aspect of the second embodiment, contacting the entire top surface of the aperture layer may form recesses in the top surface so as to generate a rough surface. Additionally or alternatively, residues of the etching material may remain on the top surface of the aperture layer. Advantageously, the top layer is cleaned after the etching process. However, due to entropy at least a small amount of the etching material remains on the top surface of the aperture layer. Such recesses or residues are not generated, if the aperture layer has been masked in order to generate a well-defined pattern of openings.

Further, according to an advantageous aspect of the second embodiment, the aperture layer defines a unique pattern of openings and the effort of the reproduction of such a light pattern is very high. Intrinsic fluctuations between material compositions in the aperture layer, the duration of the etching process, and the composition of the etching material may cause the rough surface, and thus the random pattern of openings, in particular. Conse quently, such rough surface of the aperture layer enables a unique pattern of openings resulting in highly complex patterns for light sources, which extend through said openings. As a reproduction of a light pattern created by said randomly arranged plurality of light sources is hardly possible, the label is difficult to counterfeit. According to a further advantageous embodiment, the receiving unit comprises an electromagnetic coil for inductive coupling with the time-varying electromagnetic field.

In general, wireless power techniques mainly fall into two categories, near field and far- field. Advantageously, near field or non-radiative techniques, where power is transferred over short distances by magnetic fields using inductive coupling between coils of wire, or by electric fields using capacitive coupling between metal electrodes, is used. For example, inductive coupling may be used as a wireless technology. The inductive coupling include widely used applications such as charging handheld devices like phones and electric toothbrushes, Radio-frequency identification (RFID) tags, and wirelessly charging or con tinuous wireless power transfer in implantable medical devices like artificial cardiac pacemakers, or electric vehicles. Consequently, a broad variety of usually used devices including smartphones can supply such power transmission. Thus, the label can be easily adapted to a given infrastructure of wireless power techniques.

Alternatively, in far-field or radiative techniques, also called power beaming, power is transferred by beams of electromagnetic radiation, like microwaves or laser beams. These techniques can transport energy longer distances but must be aimed at the receiver.

According to the present application, a winding is a common name for an electromagnetic coil.

According to the present application, an electromagnetic coil is an electrical conductor such as a wire in the shape of a coil, spiral or helix. According to the application, a circular segment of a coil can form an electromagnetic coil for inductive coupling. Electromagnetic coils are used in electrical engineering, in applications where electric currents interact with magnetic fields, in devices such as electric motors, generators, inductors, electromagnets, transformers, and sensor coils. An external time-varying magnetic field through the interior of the coil generates an electromagnetic field (voltage) in the conductor.

In more detail, electric and magnetic fields are created by charged particles in matter such as electrons. A stationary charge creates an electrostatic field in the space around it. A steady current of charges (direct current, DC) creates a static magnetic field around it. The above fields contain energy, but cannot carry power because they are static. However, time-varying fields can carry power. Accelerated electric charges, such as an alternating current (AC) of electrons in a wire, create time-varying electric and magnetic fields in the space around them. These fields can exert oscillating forces on the electrons in a receiving antenna of the receiving device, causing them to move back and forth. These oscillations constitute alternating currents, which can be used to power a load as the plurality of light sources.

The oscillating electric and magnetic fields surrounding moving electric charges in an antenna device of the receiving unit can be divided into two regions, depending on distance range DR from the antenna. The fields have different characteristics in these regions, and different technologies are used for transferring power.

Preferably, the power is transmitted in the near-field or non-radiative region. This means the area within about 1 wavelength (l) of the antenna. In this region the oscillating electric and magnetic fields are separate and power can be transferred via electric fields by capaci tive coupling (electrostatic induction) between metal electrodes, or via magnetic fields by inductive coupling (electromagnetic induction) between coils of wire. Preferably, the power is transferred via inductive coupling.

According to a simplified scheme, in the near field region, both fields, namely the electric fields and the magnetic fields, are localized (also referred to as non-radiative in this application) meaning that the energy stays within a short distance of the transmitter. If there is no receiving device or absorbing material within their limited range to couple to, nearly no power leaves the transmitter. In other words, the receiving device of the power supply unit, and thus, the label is unpowered. Consequently, the plurality of light sources of the light emitting unit will not emit light if no powering device is close enough to couple.

In more detail, the range of these fields is short, and depends on the size and shape of the antenna devices, which are preferably electromagnetic coils. The fields, and thus the power transmitted, decrease exponentially with distance d, e.g. 1/d ³ , so if the distance between the two antennas DR is much larger than the diameter of the antennas DA very little power will be received.

Preferably, the electromagnetic coil follows a curve formed by a spiral. Thus, flat labels, having top surface emitting the light, can be fabricated. In other words, the thickness of the labels can be reduced.

A spiral according to the application is a curve on a plane that winds around a fixed center point at a continuously increasing or decreasing distance from the point. In other words, a planar curve, that extends in both of the perpendicular directions within its plane. The groove on one side of a record closely approximates a plane spiral; note that successive loops differ in diameter.

The person skilled in the art knows, that a three-dimensional curve that turns around an axis at a constant or continuously varying distance while moving parallel to the axis may be also seen as a spiral according to the application, in other words the spiral may formed by its three-dimensional relative, namely helix.

According to an even more advantageous embodiment, the receiving unit further comprises a capacitor connected with the electromagnetic coil to form an electrical resonator. Thus, the coupling between the antennas can be greatly increased, allowing efficient transmission at somewhat greater distances.

In more detail, at short ranges up to about one antenna diameter: D _ra nge £ D _an t non resonant capacitive or inductive coupling can transfer practical amounts of power. Advantageously, resonant capacitive or inductive coupling is employed to transfer practical amounts of power up to 10 times the antenna diameter: D _rang e £ 10 D _an t.

More specifically, resonant inductive coupling is a form of inductive coupling in which power is transferred by magnetic fields between two resonant circuits (tuned circuits), one in the transmitter and one in the receiver. Each resonant circuit consists of an electromagnet ic coil connected to a capacitor, or a self-resonant coil or other resonator with internal capacitance. The two are tuned to resonate at the same resonant frequency. The resonance between the coils can greatly increase coupling and power transfer.

A further advantage of such a resonant technology is that resonant technologies are currently widely incorporated in modern inductive wireless power systems, for example in smartphones.

According to an even more advantageous embodiment, the power supply unit further comprises a rectifier for converting an alternating current extracted from the power received by the receiving device to a direct current. Consequently, the power supply unit can provide a direct current for the light emitting unit, and thus, the light output can be better controlled. E.g. in case of a VCSEL the lasing operation can be improved. Such a configuration allows to avoid a malfunction of the VCSEL when operated in the blocking direction.

Additionally, according to an even more advantageous embodiment, the power supply unit further comprises a storage capacitor for storing charge extracted from the direct current. Consequently, the light emitting unit can be powered even in a case where the power transmitting element, e.g. the smartphone, has been removed.

Furthermore, by using the storage capacitor and the VCSEL, the light emitting unit can be operated in a lasing mode until the current provided by the electrical power supply unit falls below a predetermined threshold. If the charge is below the predetermined threshold, the VCSEL operates as a light emitting diode without lasing, i.e. not providing a coherent beam and typically a larger emission angle. Thus, the emission angle of the VCSEL and the interference pattern changes when passing the transparent layer. Thus, two light patterns are generated, which are even more complex. Consequently, it becomes more severe to counterfeit the label.

Additionally, according to an even more advantageous embodiment, the power supply unit further comprises a resistor arranged between the storage capacitor and the beam generation device. Consequently, the time the light emitting unit can be powered in a case where the power transmitting element, e.g. the smartphone, has been removed can be increased.

Furthermore, by using a resistor and the VSCEL, the time between the VSCEL changes from a lasing mode to a not lasing mode depends on the value of the resistor. Consequently, the value of the resistor is a further magnitude, which defines the complexity of the pat ter, and thus, by using a resistor it becomes more severe to counterfeit the label.

According to a further advantageous embodiment, a first light source forms a first nanowire structure, wherein the core element of the first light source forming the first nanowire struc- ture has a first core diameter, and a second light source forms a second nanowire struc ture, wherein the core element of the second light source forming the second nanowire structure has a second core diameter. Further, the first core diameter is different to the second core diameter.

Thus, the physical properties of these semiconductor light sources are different. In more detail, the physical properties define the electrical parameters required so that the light source emits lights. For example, the light sources require different power to start emitting light. Thus, if the power transfer rate between the power receiving device connected to the label and a power transferring unit, for example the near field communication (NFC) mod ule of a smartphone, changes, the power rate transferred changes, and thus, a different number of light sources emits light. This enables that not only the light pattern has a spatial unique fingerprint put also a fingerprint depending on the power transferred. This effect may be employed to generate a time dependent fingerprint.

For example, the camera of the smartphone may capture the light emitted by a first plurality of light patterns comprising at least one light source. By comparing the power supplied to the label, the different light pattern can be used to increase the reliability of the pattern. Furthermore, the different diameters of the core elements are caused by the rough surface of the aperture layer. Consequently, the rough surface of the aperture layer due to the etching process ensures that the unique pattern is not only hardly forgeable due to the spatial distribution of the light pattern but also due to the different physical response to the power supplied. A simple way for changing the power supplied is by slowly approaching the power transferring unit to the label with the power receiving unit.

Even more advantageously, an intrinsic layer is formed between the core element and the shell element. The intrinsic layer may form a quantum well structure, influencing the brightness. In particular, the aperture layer causes that thickness of the intrinsic layer variable for the individual light sources. By a variable thickens, in other words a random thickness, the brightness of each light sources is influenced. Thus, the unique pattern is not only hardly forgeable due to the spatial distribution of the light pattern and/or the different physical re sponse to the power supplied of the intrinsic layer the but also due to the brightness of the light sources caused by the variable thickness of the intrinsic layer.

According to a further advantageous embodiment, the label further comprises a reflective layer. By using an reflective layer, the light emission can be increased. Further, the reflec tive layer may provide optical feedback for the lasing operation of at least one of the light sources.

Advantageously, the reflective layer is arranged between said shell element and the top surface of the aperture layer. Alternatively, the reflective layer is interposed between the aperture layer and the substrate. Alternatively, the reflective layer is extending from a bottom surface of the substrate, the bottom surface of the substrate opposing the top surface of the substrate.

A particularly simple fabrication is enabled by extending the reflective layer from the bottom surface of the substrate. For example, the reflective layer may be provided by Silicon-on- Insulator (SOI) wafers, which are commercially available. According to a further embodiment, at least one light source forms a nanowire structure, wherein the core element of the one light source forming the nanowire structure has a core diameter, and wherein the shell element of the one light source forming the nanowire struc ture has a shell diameter larger than said core diameter.

Such a configuration is particularly advantageous in connection with a reflective layer. Such a core shell structure with combined with a reflective layer forms a laser that forms a particularly bright and directed light source, which can be easily detected.

The present invention also relates to a method of fabricating a label for authentication of a product comprising the steps of: providing a light emitting unit, comprising a substrate; an aperture layer with a plurality of openings, wherein each opening extends through said aperture layer from a bottom surface of the aperture layer to an opposing top surface of the aperture layer; a plurality of light sources, each light source comprising: a core element extending from a top surface of the substrate through one of the plurality of openings formed in the aperture layer; a shell element extending on and/or around said core ele ment; wherein the shell element is spaced apart from the substrate, contacting the light emitting unit with a power supply unit for supplying power to the light emitting unit, wherein the power supply unit comprises a receiving device for extracting the power from a time- varying electromagnetic field.

The accompanying drawings are incorporated into the specification and form a part of the specification to illustrate several embodiments of the present invention. These drawings, together with the description serve to explain the principles of the invention. The drawings are merely for the purpose of illustrating the preferred and alternative examples of how the invention can be made and used, and are not to be construed as limiting the invention to only the illustrated and described embodiments. Furthermore, several aspects of the em bodiments may form— individually or in different combinations— solutions according to the present invention. The following described embodiments thus can be considered either alone or in an arbitrary combination thereof. Further features and advantages will become apparent from the following more particular description of the various embodiments of the invention, as illustrated in the accompanying drawings, in which like references refer to like elements, and wherein:

Fig. 1 A is a schematic view of a label according to the present invention; Fig. 1 B is a schematic view of a system comprising a label according to a first embodi ment of the present invention

Fig. 1C is a schematic view of a system comprising a label according to a second embodiment to the present invention

Fig. 2 is a schematic of an experimental set-up for analyzing a label;

Fig. 3 is a schematic of five unique light patterns;

Fig. 4 shows a schematic of the raw material for the label;

Fig. 5 a schematic of Fig. 4 after a step of forming a plurality of openings;

Fig. 6 a schematic of Fig. 5 after a step of forming core elements;

Fig. 7 a schematic of Fig. 6 after a step of forming shell elements;

Fig. 8 a schematic of Fig. 7 after a step of forming a protective layer;

Fig. 9 a schematic of Fig. 8 after a step of forming a contacting layer;

Fig. 10 a schematic of a light source;

Fig. 11 a schematic of Fig. 9 after a step of contacting a light emitting unit with a power supply unit;

Fig. 12 a circuit diagram of a wireless power transfer device;

Fig. 13 a top view of Fig. 11 ;

Fig. 14 an embodiment of a light emitting unit with additional reflective surface;

Fig. 15 a further embodiment of a light emitting unit with additional reflective surface; and

Fig. 16 a further embodiment of a light emitting unit with additional reflective surface.

The present invention will now be explained in more detail with reference to the Figures and firstly referring to Fig. 1A, showing a schematic view of a label 100 according to the present invention. The label 100 comprises a light emitting unit 101 for generating a shaped light beam so as to identify the label and a power supply unit 300 for supplying power to the light emitting unit 101. The light emitting unit 101 shown in Fig. 1A is a semiconductor light source, in particular a diode. The power supply unit 300 comprises a resonant circuit including an electromagnetic coil. According to a first embodiment, as shown with reference to Fig. 1 B, the light emitting unit 101 comprises a single light source 200A and a transparent layer 900 comprising a plurality of particles 902 for shaping the light generated by the diode. According to a sec ond embodiment, as shown with reference to Fig. 1 C, the light emitting unit 101 comprises a plurality of light sources 200.

As shown in Fig. 1A, the label 100 comprises, according to an advantageous embodiment, a data storage unit 500, a storage capacitor 600, a rectifier 700, and a resistor 800. The data storage unit 500 is connected to the power supply unit 300, in particular to a first end of the electromagnetic coil, and a first node, wherein the first node is connected to a parallel circuit. In more detail, the rectifier 700 is connected to the power supply unit 300, in particular to a second end of the electromagnetic coil, and a second node, wherein the second node is connected to the parallel circuit. The storage capacitor 600 is connected across the first node and the second node forming a first branch of the parallel circuit. The resistor and the light emitting unit 101 are connected in a series circuit, wherein the series circuit is connected across the first node and the second node forming a second branch of the par allel circuit.

The data storage unit 500 stores data for identifying the label. The data storage unit 500 is, for example, a NFC chip additionally adapted for communicating with a user equipment such as a smart phone. The data can be read by the user equipment when connected to the data storage unit 500 formed by the NFC chip, for example by a wireless connection.

The storage capacitor 600 is a capacitor for storing a charge. The storage capacitor is charged when power is supplied by the power supply unit 300 to the label. As soon as the power supply unit 300 is disconnected from the user equipment, i.e. not receiving power, the storage capacitor 600 is discharged. By discharging, the storage capacitor 600 sup plies the charged power to the light emitting unit 101. Consequently, the light emitting unit 101 is powered even in a case when the power supply unit 300 is not in contact with a user equipment.

The rectifier 700 is a diode for converting an alternating current supplied by the power supply unit 300 to a direct current, which is feed to the storage capacitor 600 and the light emitting unit 101. Thus, it is possible to efficiently collect charge at the storage capacitor 600. Additionally, the light emitting unit 101 can be operated more efficiently by supplying the direct current. For example, a malfunction of the light emitting unit 101 can be avoided, which may be caused when the diode is constantly supplied with power in the blocking direction.

The rectifier may be a Schottky diode enabling higher switching speeds and better system efficiency.

The resistor 800 is operable to avoid a rapid discharge of the storage capacitor 600. In more detail, in the series circuit comprising the light emitting unit 101 , the resistor 700 adapts the voltage supplied to the light emitting unit 101. The resistor 700 may be a passive device or an active device, e.g. transistors or operation amplifier. Thus, the charge stored in the storage capacitor 600 can be more efficiently supplied to the light emitting unit 101.

Furthermore, the resistor may be used to meet safety requirements. In particular, it may limit the power supplied to the light emitting unit 101 so that the light emitting unit 101 dissipates light below a predetermined threshold. For example, in case that the light emitting unit 101 is a lasing device the dissipated light to be below a predetermined threshold so that a user’s eye is protected.

According to a further advantage embodiment, not shown in Fig. 1A, a switching element may be provided in the circuit path comprising the storage capacitor 600, the resistor 700 and the light emitting unit 101. The switching element is adapted to interrupt the connection between the storage capacitor 600 and the light emitting unit 101. Such a switching element, which may be controlled by a processor, which may be part of the NFC chip, enables to control powering of the light emitting unit 101. Thus, the charge stored in the storage capacitor 6000 can be more efficiently supplied to the light emitting unit 101. According to one example, the resistor 800 formed by an active device is additionally operable as switching element.

Further, Fig. 1 B shows a schematic view of a system comprising a label 100A according to the first embodiment of the present invention. The label 100A comprises one light source 200A and the transparent layer 900. The transparent layer comprises the plurality of parti cles 902. The particles shape the beam to generate a unique pattern.

The label 100A is attached, for example glued, to a product 2000. The product 2000 ac cording to this embodiment is a medical packaging. The label 100A is powered with a wire- less power 3002, e.g. the power provided by Near-field communication (NFC) chip, from a device 3000, for example a smartphone. The light emitting unit emits light 102 that is detected by a detecting unit of the device 3000, for example a smartphone camera. Advantageously, the detected light pattern is displayed on the display 3010 of the device 3000. Further, the detected light pattern, which is unique and depends on the light pattern emitted by the label, is further analyzed.

For example, the light pattern is identified by using a database hosted by a webpage provided by a manufacturer of the product. Additionally or alternatively, the light pattern is identified by using data provided by a storage mounted together with the label on the mounting unit. For example, the storage may be a NFC chip.

For example, the NFC chip allows a digital ID of the label be transmitted to the smartphone. Thus, the measured pattern can be fast compared in a database using the ID.

According to one aspect, the light source 200A is a vertical-cavity surface-emitting laser (VCSEL). A VCSEL enables emitting light direct from the surface of the label 100A. Thus, the limited power supplied by the power supply unit can be efficiently used to generate light that is radiate away from the label.

According to a further aspect, the transparent layer 900 comprises Si02, epoxy, glue, or a polymer. These materials are transparent for the light emitted by the light source 200A. Thus, light emitted by the light source 200A is not blocked by the transparent layer 900.

According to a further aspect, the particles 902 are at least partly reflecting the generated light. Consequently, the particles 902 enable shaping the beam, however, do not completely block the beam. Thus, a signal is detectable by the user equipment 3000. For example, the particles 902 consists of material such as a metal, a dielectric, a phosphorescence, or a non-linear absorber.

According to further aspect, the transparent layer 900 comprises a bottom surface facing the light source 200A and an opposing top surface for outputting the shaped beam, and wherein a first particle is arranged closer to the top surface than a second particle. In other words, the particles are arranged in three dimensions. Thus, the path lengths between light rays emitted from the light source 200A is influenced. In particular, when the light source 200A is a laser, the three-dimensional arrangement of the particles 902 enables to generate an interference pattern which is particularly unique. Thus, as shown in Fig. 1 B, on a display 3010 of the user equipment, a particularly unique diffraction pattern is detectable on the display, when the light source 200A supplies coherent light.

According to a further aspect, if the light source 200A is not supplying coherent light, for example in the case when the light source 200A is not operated in a lasing mode, the three-dimensional arrangement of the particles shadow partly the beam and scatter the light. The shadowed and scattered beam may be alternatively or additionally used to generate a unique pattern.

According to a particularly advantageous embodiment, the light source 200A may be operated in lasing operation and in not lasing operation. Consequently, the emitted light may be shaped by two different processes depending on the power supplied to the light source 200A. In more detail, as soon as the light source 200A is operable to lase, the emitted light is sufficiently coherent; in particular, the spatial and temporal coherence is sufficient so that a distinct diffraction pattern is created. In other words, the directed beam, which is caused by the lasing, is operable to interfere.

Otherwise, when the power supplied by the power supply unit and/or the storage capacitor is not sufficient that the light source 200A emits coherent light, incoherent light is emitted by the light source 200A. Consequently, the pattern detected by the user equipment is based on the shadowing effect of the particles or by a reflection of the particles. The power supplied to the light source 200A may be for example controlled actively by the switching element: Additionally or alternatively the configuration of the electrical components may reduce the power supplied to the light source 200A after a predetermined time after disconnecting from the user equipment, namely in the time period when the storage capacitor is discharging.

Further, Fig. 1C shows a schematic view of a system comprising a label 100BB according to a second embodiment of the present invention. The label comprises a plurality of light sources 200, which are arranged on a mounting unit 400.

The label 100B is attached, for example glued, to a product 2000. The product 2000 ac cording to this embodiment is a medical packaging. The label 100B is powered with a wire less power 3002, e.g. the power provided by Near-field communication (NFC) chip, from a device 3000, for example a smartphone. The light emitting unit emits light 102 that is de tected by a detecting unit of the device 3000, for example a smartphone camera. Advantageously, the detected light pattern is displayed on the display 3010 of the device 3000. Further, the detected light pattern, which is unique and depends on the light pattern emitted by the label, is further analyzed.

For example, the light pattern is identified by using a database hosted by a webpage provided by a manufacturer of the product. Additionally or alternatively, the light pattern is identified by using data provided by a storage mounted together with the label on the mounting unit. For example, the storage may be a NFC chip.

For example, the NFC chip allows a digital ID of the label be transmitted to the smartphone. Thus, the measured pattern can be fast compared in a database using the ID. Further, with reference to Fig. 2 a schematic of an experimental set-up for analyzing a label is shown. According to this experimental set-up, the label 100B is active by an additional light source. The light emitted by the label 100B is passing through a semitransparent mirror. An optical unit then analyzes the received light.

Further, with reference to Fig. 3 five unique light patterns are shown. In particular, the first row of Fig. 3 shows five light patterns as detected with an optical unit, such as a smartphone camera. After recording the light pattern, the image may be processed by a software algorithm. An example of images processed by an algorithm to reduce the complexity of the light pattern by pixel binning is shown in the second row. Finally, the third row shows a code (Hash) resulting from the converted image, which allows an efficient comparison with the data base of the manufacturer. The identification code may be provided by a web page.

Now, with reference to Figs. 4 to 9 the fabrication method of a light emitting unit according to an advantageous embodiment is described. Firstly, Fig. 4 shows the unprocessed starting material. In particular, the label comprises a substrate 1 10 and an aperture layer 120 formed on the substrate. The substrate 110 preferably comprises Silicon, GaAs, GaN, or InP. According to an advantageous embodiment, the aperture layer 120 comprises a dielectric material, preferably SiC>2.

The substrate has a top surface 112 facing a bottom surface 122 of the aperture layer. Advantageously, the top surface 112 is contacting the bottom surface 122. Further, a top surface 123 of the aperture layer 120 is opposing the bottom surface 122 of the aperture layer 120. Further, a bottom surface 1 13 of the substrate 1 10 is opposing the top surface 1 12 of the substrate 1 10. Further, Fig. 5 shows a schematic of Fig. 4 after a step of forming a plurality of openings 124 in the aperture layer 120. In particular, a plurality of openings 124 is reaching through the aperture layer 120. More specifically, each opening 124 extends through said aperture layer 120 from the bottom surface 122 of the aperture layer 120 to the opposing top sur face 123 of the aperture layer 120. Advantageously, the aperture layer is etched. This enables an easy fabrication as standard techniques such as chemical wet etching may be used.

As further shown in Fig. 5, the top surface 123 of the aperture layer 120 further comprises a plurality of recesses 126. In particular, each recess is extending from the top surface 123 of the aperture layer 120 in the same direction as the openings 124. The recesses 126 according to the present embodiment are an artefact of the etching process to generate the openings 124. In more detail, the aperture layer 120 is etched for a few seconds so as to generate the plurality of openings 124. Advantageously, the aperture layer is etched so as to generate a thousand to a million of openings 124 on an area of 1 mm ² . Even more advantageously, the aperture layer is etched so as to generate a thousand to a hundred thousand of openings on an area of 1 mm ² . As the top surface 123 of the aperture layer 120 has not been masked with an etching resistive layer, the number of openings 124 is mainly dependent on the duration of the etching process. At the same time, recesses 126 are formed in the aperture layer. In particular, the recesses 126 are not reaching through the aperture layer.

As further shown in Fig. 5, the top surface of the aperture layer is rough. Not shown in Fig. 5 is that the top surface of the aperture layer comprises residues of the etching material, said residues of the etching material resulting from the etching process to produce the openings. Notably, the etching process is not intended to form openings at well-defined positions. Rather, the openings, also referred to as holes, are randomly distributed.

Thus, the aperture layer 120 enables random growth of light sources by prior etching of random openings 124 in this aperture layer 120. Additionally, the aperture layer 120 serves as reflection layer for optical operations such as lasing operations.

Further, Fig. 6 shows a schematic of Fig. 5 after a step of forming core elements 210 on the substrate 110, namely forming exemplary core elements 210a and 210b. In particular, the core elements 210 are growing from the top surface 112 of the substrate 1 10. More specifically, the core elements 210 are growing through the openings 124 formed in the aperture layer 120. Thus, the aperture layer 120 allows to define the positions at which the core elements 120 grow. Advantageously, the core elements are grown using molecular beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD).

Additionally, the aperture layer defines the geometrical parameters as the diameter of the core elements 120. For example, the diameter of the core elements 120b is larger than the diameter of the core elements 120a. In particular and as shown in Fig. 6, the diameter of a core element 120 depends on the diameter of the respective opening.

A further geometrical parameter of each core element 120 defined by the aperture layer 120 is the length of the core element, the length being defined in the direction perpendicular of the top surface 112 of the substrate 120. Assuming that the material for the core elements is provided at a certain flow rate, wherein the flow rate is constant, the material available for the individual core elements is different as it may depend on the individual environment influenced by recesses, contaminations, and proximal core elements competing for material. For example, core element 210a is longer than core element 120b. In particular, the length depends on the material available for the growth of the respective core element. For example, if the local density of the openings is larger, less material is available for an individual core element 210.

Thus, as shown in Fig. 6, the plurality of core elements 210 is grown on the substrate 1 10, and each core element having specific geometrical properties.

Further, Fig. 7 shows a schematic of Fig. 6 after a step of forming shell elements 220 on the core elements, namely exemplary shell elements 220a, 220b, and 220c. In particular, the shell elements 220 are extending on and/or around the core elements. For example, shell element 220c is extending on the respective core element. Further, the shell elements 220 are spaced apart from the substrate. In particular, the aperture layer 120, which is preferably formed by an isolating material, spaces the shell elements 220 from the substrate 110.

Further, each core element defines the geometrical parameters as the diameter of the shell elements 220. For example, the diameter of the shell element 220b is larger than the diameter of the shell element 220a. In particular, the diameter of the shell elements 220 depends on the diameter of the respective core element. Additionally, the diameter of the shell element may depend on the individual material flow which again may depend On the individual position of the shell elements 220 on the substrate 1 10. A further geometrical parameter of each shell element 220 defined by the core element is the length of the shell element. Assuming that the material for the shell element 220 is pro vided at a certain flow rate, wherein the flow rate is constant, the material available for the individual shell element 220 is variable. For example, shell element 220a is longer than shell element 220b. In general, the length depends on the material available for the growth of the respective shell element. For example, if the local density of the core elements is larger, less material is available for the individual shell element 220.

Further, Fig. 8 shows an advantageous embodiment of a label comprising a protective layer 130. In particular, Fig. 8 shows a schematic of Fig. 7 after a step of forming the protective layer 130 on the aperture layer 120. The protective layer 130 allows for protecting the plurality of light sources 200, wherein each light source is formed by the core element 210 and a shell element 220.

In more detail, the protective layer 130 is extending from the top surface 123 of the aper ture layer 120. Advantageously, the protective layer 130 is fabricated by a process such as sputtering, spin coating, atomic layer deposition and/or chemical vapor deposition.

According to a further advantageous embodiment, the protective layer comprises a dielectric material, such as a polymer or benzocyclobutene (BCB). Thus, the protective layer 130 can stabilizes and/ or mechanical protects the light sources 200.

Further, Fig. 9 shows an advantageous embodiment of a label further comprising a con tacting layer 140. In particular, Fig. 9 shows a schematic of Fig. 8 after a step of forming the contacting layer 140 on the protective layer 130. The contacting layer 140 allows for contacting the plurality of light sources 200, wherein each light source is formed by the by a core element 210 and a shell element 220. Further, the protective layer 130 separates the contacting layer 140 from the aperture layer 120 thereby enabling efficient charge recombination in the light sources. According to an alternative embodiment not shown in the Figures, the contacting layer is formed directly on the isolating aperture layer.

Advantageously, the contacting layer 140 comprises a metal, e.g. Au, Ag, Cu, or Ti. Alternatively, the contacting layer 140 comprises conductive polymers such as PEDOT:PSS ((poly(3,4-ethylenedioxythiophene): polystyrene sulfonic acid).

Thus, the contacting layer 140 forms a first electrical contact for the plurality of light sources 200. According to an even more advantageous embodiment, the electrical contact layer 140 can be a thin metallic layer, such as Au, Cu, or Ti that enables sufficient trans- mission, or can be formed of a transparent conducting material such as indium tin oxide (ITO). The contacts are preferably Ohmic.

Additionally, the metallic contact layer 140 may double as a second reflective layer at the top of the light sources 200, and may thereby further enhance the confinement, and thus further lower a lasing threshold.

As further illustrated in Fig. 9, a top layer 142 of the contact layer 140 forms a boundary surface of the light emitting unit. In particular, the contact layer 140 may cover a light source 200b. Additionally or alternatively, a top surface of a shell element of a light source 200a may form a part of a boundary of the light emitting unit. Advantageously, the top layer 142 of the contact layer 140 is a smooth surface. For example, shell elements extending from the top layer 142 may be removed by a mechanical or chemical process.

The substrate 110, the aperture layer 120, the plurality of light sources 200, the protective layer 130, and the contacting layer 140 form a light emitting unit 101. According to an ad vantageous embodiment not shown in the Figures, the light emitting unit is proteceted by an encapsulation structure. The encapsulation structure is for instance a layer formed on the contact layer 140.

Advantageously, the substrate 1 10 is doped so as to serve as a second contacting layer. In particular, the doping of the substrate is the same as the doping of the core and/or the dop ing of the substrate is different to the doping to the shell. For example, if the shell is p doped the substrate is n doped and/or if the core is p doped the substrate is p doped.

Further, Fig. 10 shows a further example of one of the plurality light sources 200. Each light source 200 according to this embodiment comprises a substrate 110, an aperture layer 120, a core element 210, an additional intrinsic element 230, and a shell element 220. Advantageously, the intrinsic element 230 is an inner element of the shell element 220. In particular, the intrinsic element constitutes an intrinsic semiconductor and the shell consti tutes a p- or n-type semiconductor. The intrinsic element may form a quantum well structure. The thickness of the quantum well may depend on the material flow during the growth process, which depends on the individual position of the respective light source. Thus, light intensity of the individual light source is highly dependent on the respective position on the label.

Advantageously, the light source 200 forms a nanowire laser structure. In particular, the core element 210 is an elongated element extending vertically from the silicon substrate 1 10. The shell element 220 is an elongated element formed on and around the core element 210.

Advantageously, the substrate 1 10 comprises a semiconductor material such as Si, GaAs, GaN, or InP and serves as a substrate. Even more advantageously, the substrate is a silicon substrate with a <100> silicon surface or a <111 > silicon surface.

Advantageously, the aperture layer 120 comprises a dielectric material such as S1O2 and enables random growth of the light source 200, such as a nanowire, by prior etching of random holes in this dielectric layer. The aperture layer serves also as reflection layer for lasing operation.

Advantageously, the core element 210 comprises a p-type semiconductor material such as GaAs, InP, or GaN, and serves as a p-contact. Advantageously, the intrinsic element 230 comprises an intrinsic semiconductor such as GaAs, InP, or GaN. The intrinsic element 230 serves as a recombination zone and optical gain. Advantageously, the shell element 220 comprises a n-type semiconductor such as GaAs, InP, or GaN. The shell element 220 serves as a n-contact.

According to one embodiment, the dimensions of the light source 200 are chosen in accordance with a laser wavelength of a laser signal that the light source structure 200 is supposed to emit thereby forming a nanowire laser structure. A diameter d1< l/(2·h) pre vents laser light from penetrating through the core element 210 to the underlying substrate 1 10 as the core diameter remains below an optical cutoff diameter and waveguiding in the core element 210 is efficiently avoided. As a consequence, light guided in the core-shell element on top of the aperture layer 120 is reflected at the aperture layer, thus providing optical feedback for the lasing operation of the device.

An outer diameter d2 of the shell element 220 may be at least d2> l/(2·h), and in particular d2> l/(h), wherein n denotes an index of refraction of the shell element 220. This enables efficient waveguiding inside the core-shell element along the vertical axes. Consequently, Laser light may propagate along the lengthwise direction of the core-shell element. At the end facets of the core shell element, light is reflected to resonate along the lengthwise direction of the core-shell element. The core-shell element 220 thus serves as a laser cavity.

Depending on the laser wavelength, the diameter d1 of the core element 210 may be in the range between 80 nm and 300 nm. Correspondingly, the diameter d2 of the shell element 220 may amount to at least 160 nm, in particular at least 400 nm or at least 600 nm. Further, the aperture layer 120 serves to reflect the optical light, in particular laser modes, at the end of the shell element 210 facing the substrate, and therefore provides resonant recirculation of the optical modes for lasing of the nanowire structure 200. Thus, the aper ture layer 120 enhances the reflectivity, in particular the modal reflectivity.

Further, Fig. 11 shows an advantageous embodiment of a label 100B comprising a power supply unit 300 for supplying power to the light emitting unit 101 as shown in Fig. 9 or Fig. 10. In particular, Fig. 11 shows a schematic of Fig. 9 after a step of contacting the light emitting unit 101 with the power supply unit 300.

The power supply unit 300 comprises a power receiving device 310, a first electrical connector 320, and a second electrical connector 330. The receiving device 310 extracts power from a time-varying electromagnetic field and is described in detail with reference to Fig. 12

Fig. 12 shows a circuit diagram of wireless power transfer device with a transmitting unit 3001 and receiving unit. The receiving unit comprising an electromagnetic coil 312 and a capacitor 314 forming a resonant circuit also called tank circuit. The receiving unit is con nected to a light source 200, being a diode as for example shown in Fig. 10 or Fig. 1 1 , by a first electrical connector 320 and a second electrical connector 330.

Advantageously, the transmitting unit 3001 comprises a coil enabling Near-field communication (NFC) such as coil comprised in a NFC chip of a smartphone.

According to the advantageous embodiment shown in Fig. 12, the receiving unit is a resonant circuit. The capacitor 314 consists of two plates. Advantageously, a first capacitor plate is formed by the doped substrate 1 10 and a second capacitor plate is formed by the conductive layer 140 as for example shown in Fig. 1 1. According to an alternative embodiment not shown in the Figures, the capacitor plates may be formed by additional conducting plates.

Back to Fig. 11, an embodiment is shown where the first electrical connector 320 connects the power supply unit 300 with the conductive layer 140. Thus, the shell element 220 is electrically contacted with the power supply unit 300.

The second electrical connector 330 connects the power supply unit 300 with the substrate 1 10. Thus, the core element 210 is electrically contacted with the power supply unit 300. In particular, a contacting recess is formed in the light emitting unit 101 so as to extend from a boundary surface of the light emitting unit 101 to the substrate 1 10. As shown in Fig. 11 , an opening is formed extending through or next to the contacting layer 140, through the protective layer 130, and the aperture layer 120 so that the second connector 330 contacts the substrate 1 10.

Further, Fig. 13 shows a top view of Fig. 11. In particular, the mounting unit 400 hosts the label comprising a light emitting unit 101 , as for example shown in Fig 9, and a power supplying unit comprising an electromagnetic coil 312, as for example shown in Fig. 12. For example, a wafer may be structured by a structuring process, e.g. photolithography, thereby generating the coil of the power supply unit. The same wafer may be treated with the above described process to generate the light emitting unit. Thus, the substrate additionally serves as mounting unit 400. Thus, a plurality of labels can be easily and economically fabricated on one wafer. Alternatively, the mounting unit may be an power supply unit such as a NFC tag and the light emitting unit may be connected mechanically and electrically connected to such a power supply.

The light emitting unit 101 comprises the contacting area 140 for contacting the shell elements 220 of the plurality of light sources. Further as shown in Fig. 13, the peripheral shape of the light emitting unit is asymmetric, namely is as pentagon. In other words, the peripheral shape, also known as the circumferential shape, is neither mirror-symmetric nor point-symmetrical. Thus, by analyzing the peripheral shape of the light emitting unit a pre ferred orientation can be determined more easily. Thus, the identification of the light pattern, as for example shown in Fig. 3, is simplified.

The electromagnetic coil 312 forms a spiral contacting the contacting area 140 of the light emitting unit 101 and winds around a center point of the light emitting unit 101. This arrangement enables a particular compact configuration. Further, the coil connects to a plate of the capacitor 314. Also not shown, the plate can form a frame surrounding the electro magnetic coil 314 to increase the area of the capacitor. This enables to form a resonant circuit with a compact configuration. Not shown in Fig. 13 is the second capacitor plate, which preferably is formed by the substrate, which preferably is doped as described as above.

According to one embodiment, the distance between capacitor plates is between 1 pm and 10 pm, preferably 5 pm. The area of the capacitor, in particular the area formed by oppos ing capacitor plates, is between 0.5 mm ² and 5 mm ² , preferably 1 mm ² . The electromag- netic coil has a winding number, which is the number of a closed curves in the plane around the center point, of 1 to 5000.

According to a preferred embodiment, the resonance frequency of the receiving unit is 13.56 MHz or a multiple integer thereof.

With reference to Figs. 14 to 16 embodiments are shown, wherein the light emitting unit comprises an additional reflective layer 150. Such an additional reflective layer increases the amount of light emitted from the light sources and may provide optical feedback for the lasing operation of the light sources.

Fig. 14 shows an embodiment wherein the reflective layer 150 is extending from the bottom surface 1 13 of the substrate 110. Advantageously, the substrate has a thickness less than 10 pm. Even more advantageously, the substrate has a thickness less than 100B nm.

For example, a substrate including the reflective layer may be provided by a silicon on in sulator (SOI) wafer.

Fig. 15 shows an embodiment wherein the reflective layer 150 is arranged between a bottom surface of shell element 220 and the top surface 123 of the aperture layer 120. The bottom surface of shell element 210 facing the top surface 123 of the aperture layer 120.

Such an arrangement may be fabricated by growth of sacrificial wires in the random holes of aperture layer 120 during a first fabrication step. The resulting structure is then coated with the reflective layer 150, preferably an oxide layer, whereby the original aperture layer 120 thickens. The sacrificial wires are then removed, e.g. thermally evaporated or etched. In the remaining thick layer, comprising the aperture layer 120 and the reflective layer 150, the core elements are formed as for example shown in Fig. 6. Such an arrangement offers an additional level of protection against counterfeiting, as the shape of the openings is additionally determined by the shape of the first sacrificial wires, however these sacrificial wires have been removed at all times.

Further, as shown in Fig. 16, the reflective layer 150 is interposed between the aperture layer 120 and the substrate 110.

Such a reflective layer 150 may be generated by firstly forming a thick reflective layer 150 on the substrate 1 10. Then, the aperture layer 120 is formed on the thick reflective layer 150. Then, this aperture layer 120 is etched, as for example described with reference Fig. 5. The random opening pattern formed in the aperture layer 120 can then be transferred to the reflection layer 150 by a dry etching step by using the aperture layer 120 as a mask.

Although in the above figures only an embodiment is shown wherein the core element 210 and the shell element 220 are cylindrical, both, the core element 210 and the shell element 220, may be hexagonal or triangular. However, depending on the materials used in the fabrication process, other shapes may likewise be employed.

Although in the above figures only an embodiment is shown, where the electromagnetic coil is formed on the light emitting unit, the electromagnetic coil may be formed on the sub strate.