* * *

The present invention refers to an apparatus for conveying laser radiation beams emitted by a plurality of power laser sources toward an optical collector device, in particular a multi-mode optical fiber, said apparatus including a set of free light propagating optical components to convey said laser radiation beams among free light propagation spans.

In the field of applications for power lasers, for example for laser processing machines, such as laser cutting machines, it is usually important to be able to convey the laser beams from a plurality of laser sources, for example semiconductor power lasers, into a single optical device, usually a multi-mode optic fiber, so to sum the powers and obtain a laser beam with augmented power for processing or for pumping an active fiber laser.

The use of fiber optic combiners for this purpose is known. However, such components are fragile, delicate and expensive.

Apparatuses are known that use free light propagating components or bulk optical components in place of fiber components. For example the use of multiple mirror systems for combining laser beams from different sources is known. From the document WO2007/061509 the use is known of semiconductor lasers mounted on a tier structure for sending non-interfering beams that can then be combined using conventional optical combining devices. These devices do not permit the use of a high number of laser sources, typically being able to operate with about ten sources.

The use is also known, for example from US 6 663 785 of a plurality of laser sources that emit light at wavelengths that vary slightly from each other and use of optical components such as diffraction gradients, in bulk or superficial, for combining the different optical phases. However, the use of multiple laser sources each operating at a wavelength that must be precisely fixed, as well as having a wavelength that differs from those of the other sources, has serious disadvantages in terms of construction costs, thermal stabilisation and construction difficulties.

The present invention has the object of providing an apparatus for conveying laser radiation beams emitted from a plurality of power laser sources that overcomes the drawbacks of the known art, providing in particular an economical apparatus of simple construction, flexible in applications and simple to stabilise thermally.

According to the present invention, such object is achieved by means of an apparatus for conveying laser radiation having the characteristics specifically recalled in the claims that follow. The invention also regards a corresponding laser radiation conveying procedure .

The apparatus for conveying laser radiation from a plurality of power laser sources according to the invention provides a focused laser beam by means of a device for free space propagation that is simple and economical to produce, having an arrangement that is simple to construct and not sensitive to variations in wavelength or thermal effects.

Further characteristics and advantages of the invention will be clear from the descriptions that follow, made with reference to the annexed drawings, provided by way of non-limiting example only, in which:

- figure 1 is a schematic lateral section of an apparatus according to the invention;

figure 2 is a schematic plan view of the apparatus in figure 1 ;

- figure 3 is a schematic lateral view of a detail of a first component of the apparatus in figure 1 ;

- figure 4 is a schematic plan view of the first component of the apparatus in figure 1 ;

- figure 5 is a diagram illustrating the operation of the apparatus in figure 1 ;

- figure 6 is a schematic plan view of the second component of the apparatus in figure 1 ;

figure 7 is a schematic lateral view of the second component of the apparatus in figure 1 ;

- figure 8 is a schematic lateral view of a detail of a third component of the apparatus in figure 1;

- figure 9 is a schematic plan view of the third component of the apparatus in figure 1;

- figure 10 is a schematic lateral view of a fourth component of the apparatus in figure 1 ;

- figure 11 is a schematic section of a variant embodiment of the first component in figure 3.

Briefly, for the purpose of conveying the laser radiation from a plurality of laser sources, the apparatus according to the invention includes a set of free light propagation or bulk components and free space propagation spans. The set of bulk optical components, in addition to standard components such as aspherical and cylindrical lenses, which operate to collimate and focus the laser beam according to determined criteria, include a component for focussing onto a collector, in particular onto a multi-mode fiber optic core, which preferably functions to pump a fiber optic laser. Such focussing component has rotation symmetry around an axis of symmetry, in particular vertical, so to have the same refractive properties with respect to all of the laser beams incident thereon that propagate in a plane orthogonal to such axis of symmetry. Such focussing component having a symmetry of rotation has, with respect to the path of one of the incident laser beams, ^' a first rotational optical surface forming a first optical interface and a second optical surface forming a second optical interface. The first rotational optical surface is configured for focussing the incident beam on a plane passing through the axis of symmetry, while the second surface forms an angle with such axis of symmetry, in order to make a total reflection of the rays of the incident laser beam toward a focus on the axis of symmetry where the collector device is located. This is accomplished by making the laser beam to pass through a base surface of the focussing component. Such base surface is preferably configured for providing a further refraction of the reflected beam from the second surface to move the final focal point closer on the axis of symmetry. Used herein, the term optical interface intends a surface separating media with different refraction indices. The set of bulk optical component includes also optical components, in particular aspherical lenses for collimating the beam emitted for the laser source, and components for focussing such collimated beam on the axis of symmetry, in particular vertical, of the focussing component, in particular obtained by means of a cylindrical lens. The aspherical lenses preferably have their focus located in correspondence to zones of emission of the laser devices,, for collimating the laser beams in a direction that corresponds with the major aperture and with the aperture depending on the size of the emission zone, toward the cylindrical lens, which focuses on the vertical axis of the focussing component. The focussing component preferably has a toroidal shape that defines the first surface, the furthest radially from the axis of symmetry, including a conical central depression, forming the second surface with a determined aperture angle, adapted for focussing all rays of the incident laser beam onto the focussing component in a given region of the collector device, in particular the core of an optical fiber located above or below the focussing component on the axis of symmetry.

Sizing is preferably done so that the aperture in the radial direction of the beam exiting from the focussing component is smaller than the semi-opening of the acceptance cone of the fiber.

Figure 1 shows a partial schematic lateral section of a branch of an apparatus according to the invention, indicated in its entirety with reference 10. The apparatus in general has a plurality of branches 10 on which are propagated respective laser beams 14 emitted from laser sources 30 towards a focussing component 17, or focussing optical device, arranged in a centre of symmetry in which one of its axes of symmetry VA is located. Figure 2 shows a corresponding schematic plan view. The apparatus according to the present invention in general has radial symmetry according to which the branches 10 are arranged and one of the optical sets is described herein, which can be arranged along one of the radii, in particular along one of the radii of a circular support plate 40. Thus, an L support 11 for a laser source 30 includes a horizontal base 12 and a vertical column 13. Such vertical column 13 includes a pad 13a on a lateral wall for attaching the laser source 30, i.e., a semiconductor laser on a chip, positioned vertically, with respect to a horizontal plane defined by the circular plate 40 on which the support base 11 rests. The laser source 30 is for example an 8 Bookham SES8-15-901 high power diode laser, having an emission width in the plane parallel to the base of the chip of 90 microns and a height of between 1 and 2 microns . The aperture in the plane parallel to the base is 8° FWHM, while the aperture in the plane parallel to the base is 29° FWHM. The emission wavelength is 915 nm and the package dimensions are 3.9 x 4.05 x 0.55 mm. The laser source 30 is preferably positioned so that its direction of greatest beam aperture is perpendicular to the axis of symmetry VA, in particular also to the axis of a collecting optical fiber 18 operating as the collector device arranged aligned with said axis VA.

The section axis on which figure 1 is drawn in this case is radial tangent to the base 12.

Also present on the base 12 of the support 11, in addition to the laser source 30, is a seat 12a shaped for mounting an aspherical lens 15 that receives a laser beam 14 emitted by the device 30, from its emission portion 14a, in which the rays of the laser beam 14 are divergent. The aspherical lens 15 supplies a collimated beam 14b in exit, i.e., parallelized in the horizontal plane along a horizontal axis HA, while in the vertical plane- the beam 14b remains slightly divergent. Also arranged on the plate 40 along the axis HA of the beam 14A is a cylindrical lens 16 that provides a beam 14c focused on the axis of symmetry VA, vertical with respect to the plane identified by the plate 40, of the focussing component 17.

Figures 6 and 7 show the thick circular aluminium plate 40 in greater detail, including a central flat part 41, on which the focussing component is mounted and a peripheral flat part 42 at a lower level on which are mounted the copper L-supports 11 bearing the laser source 30 and aspherical lens 15 and, in front of such components in the path of the laser beam 14, the cylindrical lens 16.

Figure 6, as mentioned, shows a plan view of the plate 40, supporting more branches 10 of the apparatus according to the invention, arranged along the radii of the circumference identified by the plate 40, at various angular positions. Figure 7 shows such plate 40 in detail, at a magnification of 1:2 with respect to figure 6, viewed in lateral section along an axis B corresponding to a diameter of the plate 40 along the axis of the laser beam 14. From figures 6 and 7 it can be seen that such plate 40 includes also an annular support pad 43, more noticeable with respect to the central pad 41, located inside a central hole 44 that provides access to a circular depression- 45 on the lower face of the plate 40, in which the multimodal fiber optic collector 18 is arranged as a collector device, with its input side 18a arranged horizontally, i.e., parallel to the plane defined by the plate 40. The optical fiber 18 in the example has a numerical aperture AP of 0.2 and a core diameter of 200 microns. Moreover, in the example shown the thickness S of the plate 40 in correspondence to the peripheral wall 42 is 25 mm, a height hp of the pad 43 is 15 mm with respect to the peripheral plane 42. The central hole 44 has a diameter Df of 14 mm. The plate 40 has a diameter Dp of 74 cm.

The collecting optical fiber 18 is shown in figure 1 arranged below the plate 40 on a positioner 19, which can be present whenever it is necessary to adjust the position, in particular for fine centering in the two ^' horizontal directions and adjustment of the vertical position .

The optical fiber 18 can alternatively be mounted above the focussing component 17, inverting such focussing component 17. The micrometric positioner 19, if present, is generally anchored to the plate 40, for example with steel pins, and even though they can generally be used with the optical fiber 18 either arranged above or arranged below, mounting below the plate 40 avoids having positioner support pins that can interfere with source beams placed in other angular positions. As said, in figure 6 further branches 10 are visible, the sources 30 and lenses 15 and 16 for which are arranged on the peripheral plane 42 at different angular positions, sending their respective beams 14 toward the single focussing component 17 in the centre of the radial geometry.

The source lasers 30 are welded to the supports 11 to which they are fixed, for example by means of brazing, also aluminium mountings containing the aspherical lens 15. In front of the aspherical lenses 15, for example glued directly to the circular plate 40 and with active alignment, are the cylindrical lenses 16, which naturally are also arranged in corresponding mountings .

The laser 30, as was said, is mounted vertically on the support 11, and not horizontally, because it is necessary that the beam 14b collimated by the aspherical lens 15 have an extremely low aperture in the plane perpendicular to the axis of symmetry of the toroidal focuser 17, i.e., the axis of symmetry VTA, which is vertical. In fact, the thickness of the laser source 30 being of a few microns, the aperture in that direction is extremely low and limited only to the diffraction. In the horizontal plane, focussing by means of the cylindrical lens 16, a sufficiently small spot can be obtained, less than the core diameter of the collecting optical fiber 18, which in the example is 200 microns. On the vertical plane, i.e., on the plane passing through the axis of symmetry of the aperture of the beam 14b after the aspherical lens 15 depends on the half length of the laser source 30, in the example described of 45 microns, and of the focal length of the aspherical lens 15, in the example of about one centimetre. The aperture corresponds to the half length divided by the focal length. The cylindrical lens 16 however does not produce an effect in this direction and the beam 14c arrives on the focussing component 17 only a little wider with respect to the portion of the beam 14b exiting the aspherical lens 15. In this part of optical path of the laser beam 14 curvature of the external surface of the toroid that forms the focussing component 17 is provided, in the plane containing the vertical axis VA, to focus the beam 14c, with a focal length that is much shorter, in particular several centimetres, than that of the cylindrical lens 15, which is about 20 centimetres. Given that also in this direction the final size of the spot on the collecting fiber 18 is obtained by multiplying the focal length by the aperture, and given that now the focal length is much shorter, it is possible to focus on a spot within the 200 micron width of the core of the fiber 18. The circular plate 40 satisfies the double functions of supporting the plurality of branches of the apparatus 10 and dissipating the heat generated by the laser sources 30. The radial symmetry of the support and corresponding arrangement of the branches 10 with respect to the focussing component 17 confers robustness against misalignments due to thermal expansion, especially if the laser beams 14 are arranged equidistant and symmetrical along the circumference of the plate 40. The positions and working tolerances related to the support surfaces of the supports 11, of the cylindrical lenses 16 and of the focussing component 17 are preferably selected so to guarantee passive alignment in the vertical direction. The use of aluminium for the plate 40 provides a good heat sink, though it is possible to use other materials with equivalent mechanical and thermal properties. The circular depression 45 on the lower face of the plate 40 permits ^■ insertion of a cooling system that circulates water or another cooling liquid to dissipate heat, if needed, on the side opposite the laser source 30.

Figures 3 and 4 show a view in plan of the focussing component 17 and a section along an axis A-A corresponding to its diameter in the direction of the axis of the incident beam 14. Such focussing component 17 is made, for example, of TAC4 glass produced by Hoya . The focussing component 17 in general has a toroidal shape, with a rotational symmetry around the vertical axis VA and includes a lateral surface 171, and two flat base areas, an upper surface 172a and a lower surface 172b, respectively. A conical hole 173 is present in the upper surface 172a, the corresponding cone identified by it having its base in the upper surface 172a and its vertex near the lower surface 172. To facilitate machining, the conical hole 173 can also be a through-hole, i.e., an axial hole, obtained by a machining instrument to reach the vertex of the conical hole 173, may be present on the lower surface 172b.

The conical hole 173, being a right cone along said vertical axis of symmetry VA also identifies a surface with rotational symmetry and a lateral wall of the cone 173a, i.e., a conical optical surface between the glass of the toroid and the air or other medium external to the focussing component 17.

In the example described herein the focussing component 17 has a diameter D of 13.8 mm, a height h of 5 mm. The optical axis of the laser beam 14, corresponding to a horizontal axis HA, is aligned to strike the lateral surface 171 at a height h/2 of 2.5 mm, while the vertex of the conical hole has a distance d of 2 mm from such optical axis of the beam 14.

The conical hole 173 has an aperture angle 2Φ, which is 93.95° in the example shown.

The lateral surface 171 of the toroid has a curvature radius of 15 mm and a taper coefficient K=0.

Figure 5 shows a partial lateral view of the focussing component 17 during operation of the apparatus 10. Reference 141 indicates an incident ray of the laser beam 14 from the laser source 30 of a branch 10 of the apparatus according to the invention, in this case the ray along the horizontal axis. Such ray 141 is refracted by the curved surface 171 and strikes the conical optical surface 173a at an angle β with respect to such surface, being then reflected at an angle β of egual value towards the lower surface 172b, with the normal to which it forms an angle γ. Therefore, exiting from the lower surface 172b is a refracted ray in the beam 14d toward the fiber 18 at an angle of a with respect to the vertical axis VA. Considering next a laser ray 142 parallel to the ray 141, for example incident at the highest vertical level on the conical optical surface 173a, Θ indicate the angle at which such ray 142 exits in beam 14d, after reflection from the optical surface 173a and refraction on the lower surface 173b toward the fiber 18. Such angle Θ is calculated starting from the angle a, i.e., the sum of angles Θ and a indicates the angle formed with the vertical axis VA of ray 142 exiting from the focussing component 17. Also, reference 143 indicates a ray of the beam 14 at the lowest level of the beam 14 that is reflected along the vertical axis VA . It can be shown that the following relationships between the angles shown in figure 5 are valid. The angle γ formed by ray 141 with respect to the normal axis to the surface 173 in its point of incidence is: γ=π-β-(π/2+ β)= π/2-2β (1)

From Snell's law, operating in air with a refraction index of 1 is:

sin (γ) = (1/n) sin (a) =cos (2β) (2) Φ= π/2-β (3) β= (1/2) arcos [ (1/n) sin (a) ] (4)

It is possible to work with the approximation according to which an angle Ψ at which the beam 14d is focused on the fiber 18 is:

Ψ = Θ + a ~ 2a (5) Obtaining in this way the link between the numerical aperture AN of the fiber 18 and the angle Ψ, as, approximately AN=sin( ) . The numerical aperture AN of the fiber being known, this allows calculation of the angle of aperture 2Φ of the conical hole, which is a function of the angle Ψ through relationships (1) (5) described above.

Figures 8 and 9 show lateral and plan views of an exemplar form of the copper support 11 on which the semiconductor laser source 30 is fixed, for example by means of brazing the previously gilded support 11. Such support comprises in the base 12 the shaped part 12a so to allow gluing of the aluminium mount containing the aspherical lens 15. The correct position can also be identified in active mode, collimating the beam, in the example described in the present description, at a distance of about 2 metres. Also visible in figures 8 and 9 is the pad 13a for the chip having a dimensions dz of 4.1 mm, compatible with the package of the laser source 30.

A length Ls of the support 11, 9.6 mm in the example, is selected for example so to guarantee rigidity and good heat transfer between the laser 30 and the base 12 in contact with the plate 40. At the same time, such length Ls must be sufficiently thin to permit the mounting of many lasers, for example 99, along the circumference of the plate 40, in proximity of the external perimeter of the peripheral plane 42. With the length Ls adopted, the difference in temperature between the zone near the laser 30 and the base 12 does not exceed 2°C.

To facilitate positioning of the focussing component 17 the diameter of the pad 43 is the same as that of the focussing component 1 . The focussing component 17 can be fixed to the pad 43 with liquid adhesive for lenses.

The multimodal optical fiber 18 is positioned over (or under) the focussing component 17 at a position that possibly permits maximising the collected power, in particular a vertical position that is regulated for example by means of the positioner. For regulating the position in the horizontal plane of the multimodal fiber 18, which is preferably central and symmetrical with respect to the focuser 17, laser light from a He- Ne laser can be sent into the multimodal fiber 18 and the annular beam that exits the toroidal focuser 17 can be monitored, looking for a beam with radially uniform ring, i.e., with a vertical extension along the z axis, that ^' remains the same in any radial direction. Preferably the fiber 18 is positioned with a maximum error of 10 microns.

The copper support 11 with laser source 30 and aspherical lens 15 is preferably positioned after the focuser 17 on the plate 40. The position of the support 11 is regulated so that the collimated beam 14 produced is directed as much as possible toward the centre of the focuser 17. In practice, it is possible to identify such position by turning on the laser source and monitoring the radiation collected by the fiber, the correct position being that which maximises the signal. The support 11 is attached to the circular plate 40, for example by means of screws and brackets.

Preferably the cylindrical lens 16, which in the example shown has a focal length of 200 mm, is positioned as the last component on the beam 14, with a lateral positioning error of the cylindrical lens 16 not greater than +/- 5 microns.

As was said, it is also possible alternatively to operate using passive alignment of components 30, 15 and 16 of the branches of the apparatus 10, positioning the focuser 17 on the plate 40 so that its axis of symmetry corresponds to the designated focus point of the branches and successively placing the various branches 10 with the sources at the angular positions envisioned. Positioning, simplified by the exact radial positioning, i.e., focussing on the axis of symmetry, is important, but small focussing errors generally result in only minor widening of the final spot. Moreover, as was said, possible thermal drift has less influence on radial misalignments. Greater care must be taken in aligning the axis of the beam 14 on the vertical axis VA, i.e., on the centre of symmetry.

Figure 10 shows the aspherical lens 15, which has a first side 151 in the direction of the incident beam 14, i.e., the portion 14a of divergent emission, with a first minor curvature, and a second side 152, where the beam exits, with a greater curvature. In the example shown, the lens 15 has a diameter DA of 14 mm and a thickness along the axis SA of 3.5 mm. By way of example, the first side 151 has a curvature radius R = -107.51, conic constant K egual to zero, and further polynomial coefficients, C2 = 0.0, C4 = 0.0, C6 = 0.0, C8 = -5.916877E-11, CIO = -6.005851E-14 , C12 = - 3.937348E-13, C14 = -1.200E-16, C16 = - 1.584063E- 16. The second side 152 has a curvature radius R = 8.02267, K = -0.510145, C2 = - 1.893247E-8 , C4 = 5.208071E-6, C6 = 5.200896E-8, C8 = 1.857020E-9, CIO = 5.321945E-11, C12 = 3.047752E-13. C14 = - .378764E-15 , C16 = -5.055326E-16.

Figure 11 shows a variant embodiment 27 of the focussing component 17 in figure 3. Such focussing component 37 includes a toroidal ring 27a, including a lateral surface 271 substantially analogous to the lateral surface 171 of the focussing component 17 and therefore functioning as a focussing surface for the incident beam in the direction perpendicular to the axis of symmetry VA . Such toroid 27a includes a cylindrical central through-hole 274 in which a conical element 27b is inserted such that its axis is aligned with the axis of symmetry VA; such conical element 27b comprising a lateral wall of the cone 273a to define a conical optical surface, in a way analogous with the wall 173a in figure 3.

Therefore, the focussing component 27 uses the external surface 273 of the toroid 27a as the first rotational optical surface that forms a first optical interface with respect to the path of the incident beams of laser radiation to provide focussing in a plane of the axis of symmetry VA, while the lateral surface 273a of the cone 27b forms the second rotational optical surface, forming the angle Φ with such axis of symmetry suitable to cause total reflection of the incident beams of laser radiation toward a focus on such axis of symmetry VA, in particular through the cylindrical hole 274, reaching the collector device, not shown in figure 11, but arranged in the axis of symmetry VA, in this case above the focussing component 27.

The focussing component 27 demonstrates that possibility of forming the focussing surface and the total reflecting surface by means of two associated optical elements, instead of by means of a single element .

In variant embodiments it is possible to substitute the single laser source 30 with a chip containing more lasers arranged in parallel along the direction of the laser beam 14. This permits incrementing the total power emitted from the multimodal fiber 18 or a reduction in the number of devices arranged around the focussing component 17. It is possible to use also multiple lasers developed vertically, one above another. For using such multiple lasers, it is envisioned that the aspherical lens be replaced with a rank of diffractive lenses capable of collimating each laser beam separately. Such diffractive lenses have a smaller focus than the aspherical lens 15, to insure that each lens receives only the radiation from one among the multiple lasers. Preferably, in this case chips having few well-spaced lasers and narrow apertures in the direction parallel to the chip are used.

Thus, the apparatus according to the invention is economical, simple to construct, flexible to apply and simple to stabilise thermally.

The apparatus according to the invention advantageously envisions the use of a focussing component that is a bulk component in optical glass and can be made economically, for example by casting. This focussing component with rotational symmetry permits the use of a single optical component for focussing beams from sources in different angular positions onto the fiber. Therefore, there are none of the mechanical interference problems that would arise if many bulk optical components, such as lenses or mirrors, were needed to deflect the laser beams of different branches in the region radially closer to the collecting fiber.

The apparatus according to the invention, operating essentially on the basis of Snell's law, advantageously provides sources operating at less precise wavelengths with respect to nominal values, without affecting function.

The apparatus according to the invention allows operating with a higher number of laser sources, with respect to known solutions, permitting arrangement of at least one hundred sources in a plane around the focussing component.

Moreover, because the laser sources dissipate several tens of watts, creating thermal problems, the apparatus according ^' to the invention provides a structure that permits easy disposal of the heat and at the same time guarantees a certain mechanical rigidity that prevents misalignments, in particular between the central focussing component and the group constituting the laser, the aspherical lens and the cylindrical lens. The overall system has a substantially radial arrangement around the focussing component, deriving from the rotational symmetry adopted, which permits arrangement of bodies that dissipate heat to the outside and positioning of the focuser at the centre of symmetry. Such arrangement causes any possible thermal expansion to act radially and this permits easier focussing and easier passive alignment studies. This advantageously permits for example, separate production of the symmetric support equipped with the rotationally symmetrical focuser and subsequent addition of the groups of components of the branches, for example positioning the source, aspherical and cylindrical lenses on references suitable for establishing focus through purely passive alignment, exploiting the low sensitivity to radial misalignments, or performing a partially passive alignment by adjusting the position of the cylindrical lens possibly angularly or radially misaligned .

The apparatus according to the invention advantageously permits, through use of a focuser with rotational symmetry, the use also of passive alignment technology for the laser sources and optical components of the branches, which by design tend to focus on a point corresponding to the axis of symmetry, where the focussing component can then be positioned, also in a successive phase separate from assembly of the apparatus .

Naturally, without prejudice to principle of the finding, the details of construction and the embodiments may vary, even appreciably, with reference to what has been described and illustrated by way of example only, without departing from the scope of the present invention.

It is clear that the axis of symmetry of the toroidal focussing component, defined as vertical in the examples described, in general can have a different orientation in space, and for example be horizontal, while the plane in which the sources are arranged remains orthogonal to it, and therefore for example vertical, while the core of the optical fiber that functions as the collector remains aligned with such axis of symmetry.

The focussing component has a lower surface, i.e., the surface facing the optical fiber, that is preferably flat. Such lower surface can also be adapted to cause a minimum of refraction. In particular, the refractive effect of the lower surface can also be not substantially present, whenever, for example the optical collecting fiber is placed in direct contact with the lower surface of the focussing component, or in any case optically connected without substantial variations in refractive index, for example by means of an interposed block of glass or quartz, in place of the tract of air. Such block can be envisioned both for protecting the beam from ^' interference and for dissipating the power of the laser beam and thermal insulation.

In place of the plate supporting the optical components of the system, another support structure having radial symmetry around the centre of symmetry where the focussing component is arranged, for example a structure of bars, races, or support arms that project radially in the horizontal plane of the central support element on which the focussing component is housed can be used for the respective branches on which the laser beams are propagated.

The radial symmetry around a centre of symmetry in which the focussing component lies and below or above which the optical fiber is arranged along the axis of symmetry of the focussing component also permits, advantageously, in variant embodiments, easy positioning of a conduit for circulating cooling liquid, for example water, for the dissipation of heat around the fiber or beneath the sources. In a preferred embodiment, a quarts block is interposed in place of the tract of air between the monomodal optical fiber and the focussing component, to avoid dissipating the power of laser in the fiber. Around such quartz block a circuit of cooling liquid is arranged to optimise thermal dissipation.

The conical hole of the focuser works by total reflection, but in variant embodiments it is possible to use metallisation of part ^' or all of the surface of such hole, to reflect the beam toward the collector component .

Possible fields of application of the proposed system include laser pumping units for powerful fiber lasers to use, for example, in mechanical machining, and in general in all laser machining compatible with apparatus for conveying laser radiation described.