Interference gain laser device

Abstract

A laser apparatus configured to emit coherent optical radiation is described, comprising an optical beam amplifier system (12) comprising a single interferometric optical amplifier arrangement (20) or a plurality of serially connected interferometric optical amplifier arrangements (20, 20'). Each of the interferometric optical amplifier arrangements (20) comprises a Mach-Zehnder interferometer with an amplifier arm (20a) including an active gain region (G) and a passive propagation arm (20b) without a gain region. The laser apparatus (10) further comprises an optical return path (14) for directing a beam (B0) output from the optical beam amplifier system (12) to an input of the optical beam amplifier system to form an optical ring resonator structure, and a radiation output element arranged to extract a portion of the beam output from the amplifier system and deliver the extracted portion as output radiation (BL) of the laser apparatus.

Description

[Technical Field]

[0001] The present invention relates to a laser device, and is not particularly limited to a semiconductor laser device. [Background technology]

[0002] One of the main limitations of this particular class of lasers is the impossibility of achieving high optical powers, on the order of kilowatts or more, from a single laser diode, exceeding tens of watts.

[0003] This power is required in certain industrial processes, such as the industrial processing of materials and metal plates and shapes, and in particular, lasers are used as thermal tools for various applications that depend on the interaction parameters of the laser beam with the material being processed, specifically the energy density per unit volume of incident laser beam on the material, and the interaction time interval.

[0004] For example, metal materials have a low energy density (surface 1mm 2 The hardening process is carried out by directing a beam of light (on the order of tens of watts per minute) over a long period of time (on the order of a few seconds), while the same metal material can be subjected to high energy density (on the order of femtoseconds or picoseconds) over a period of time (on the order of surface 1 mm). 2 The photoablation process is performed by directing light (on the order of tens of MW per unit). In the intermediate range of increasing energy density and decreasing processing time, welding, cutting, drilling, engraving, and marking processes can be performed by controlling these parameters.

[0005] Laser equipment is also used in additive processes, where the material is supplied, for example, in the form of a filament emitted by a nozzle or in the form of a powder, or may exist in the form of a powder bed, and is therefore melted by laser radiation, followed by the re-solidification of the material to obtain a 3D print.

[0006] In prior art, the coupling of different laser beams is used to obtain high optical power on the order of magnitude mentioned above.

[0007] Different laser beams can be coupled in various ways based on the individual relationships of the laser emission devices, for example, by coupling beams that are incoherent with each other (incoherent coupling), by coupling beams at wavelength, and by coupling beams that are coherent with each other (coherent coupling).

[0008] Unfortunately, incoherent beam coupling yields a whole beam whose radiance (considering both total optical power and the resulting beam quality) does not exceed the radiance of a single laser. Furthermore, in incoherent coupling techniques, there is no relationship between the beams involved (neither phase nor spectrum), and the optical power increases with increasing the number of laser-emitting devices involved, at the expense of the overall quality of the resulting beam.

[0009] By coupling wavelength beams or coherent beams, it is possible to increase the emitted light power while maintaining the quality of the resulting beam, and the radiance increases linearly with the number of coupled laser-emitting devices.

[0010] In particular, in wavelength beam coupling techniques, each laser light-emitting device operates at a different wavelength, and the use of dispersive optical elements allows for the superposition of the beams to be coupled. Consequently, the increase in power is achieved at the expense of the beam's spectral quality.

[0011] On the other hand, in architectures for coherent beam coupling, all laser emitting devices operate at the same wavelength, a specific phase relationship exists, and constructive interference can occur between individual beams.

[0012] The use of one of the techniques mentioned depends on applications that require high optical power.

[0013] For example, in order to create a type of high-brightness light source used for laser processing of materials, it is necessary to adopt an architecture for wavelength or coherent beam combination. Among these, the currently most common solution is the former, and the main reason is due to the greater ease of its implementation. In fact, since these are methods for combining different laser beams, that is, beams emitted by different laser light-emitting devices, the main difficulty in creating an architecture for coherent beam combination lies in the active control of the phase relationships necessary to obtain constructive interference between the various beams involved.

[0014] This difficulty becomes even greater in semiconductor laser devices, where thermal instability and non-linear phenomena can significantly change the phase of the beam. Summary of the Invention Problems to be Solved by the Invention

[0015] The present invention aims to provide an alternative solution to the existing architectures of laser devices and systems, which is easy to manufacture and can emit coherent beams with high optical power.

[0016] In particular, the present invention aims to provide a laser device that is robust and easy to manufacture, thereby increasing the maximum power that can be extracted from a semiconductor laser compared to the prior art. Means for Solving the Problems

[0017] According to the present invention, this object is achieved by a laser device having the features described in claim 1.

[0018] Specific embodiments form the subject matter of the dependent claims, the content of which should be understood as an integral part of this specification.

[0019] In summary, the present invention is based on the arrangement of an optical amplifier system, i.e., an optical gain means, in a single optical resonance structure, such as a resonant cavity (including a Fabry-Perot cavity) or an optical ring path. The laser device of the present invention consists of a single light-emitting device and is not a combination of a plurality of light-emitting devices. The gain means includes a stage or a plurality of amplifier stages connected in series or in cascade, each of which achieves the splitting of an incident light beam into a pair of secondary beams and guides the two secondary beams through an amplified branch and an unperturbed, i.e., non-amplified, propagation branch, and finally combines them in an interference beam. The splitting of the incident light beam is achieved such that most of the power of the incident beam is guided towards the non-amplified propagation branch.

[0020] In a currently preferred embodiment, the amplified branch includes a semiconductor optical amplifier that is powered by an injection current to obtain a population inversion condition of charge carriers confined in the active region, and the resulting radiative recombination and coherent photon emission occur in phase with the photons passing through the incident light beam. Advantageously, by splitting the beam, the power incident on the semiconductor optical amplifier can be reduced. Compared with a standard amplifier, various problems related to the circulating power are solved at the same injection current, for example, damage to the semiconductor surface, thermal problems related to power absorption, and non-linear phenomena are eliminated. This configuration results in a more reliable device and a longer average life.

[0021] An optical path that returns the interference beam to the input of the gain means forms a resonant structure equipped with an amplifier system, for example, in the form of a resonant cavity or a resonant ring circuit. The beam propagation may occur in a single propagation direction or both.

[0022] In current preferred embodiments with free-space optical transmission, the amplifier stage includes one or more interference optical amplification arrangements, each interference optical amplifier stage having beam splitting and coupling means at the input and output, for example, optical devices fabricated as prisms or translucent mirrors, and the return optical path has reflective and refractive optics configured to guide the beam and form spatially. Alternatively, in embodiments with guided or integrated optics, the optical beam is guided by confinement in an optical guide obtained on a substrate, for example on a substrate suitable for mounting a semiconductor optical amplifier, and the splitting and recombination of the optical beam is performed via beam splitting and coupling means obtained using controlled mode coupling techniques between the optical guides described above.

[0023] The advantage of the interference amplifier structure is the possibility of diverting a portion of the incident light power from the amplification branch, thereby preventing the occurrence of saturation conditions in the active region of the optical amplifier, which can limit its amplification characteristics.

[0024] Compared to a simple semiconductor optical amplifier, a semiconductor interference optical amplifier has lower gain but higher saturation power. The behavior of the interference amplifier moves even further away from that of a simple amplifier; the larger the portion of the incident beam guided through the non-amplified propagation branch, the greater the gain through the amplified branch operating further from the saturation point. Furthermore, there are fewer power-related phenomena that degrade the overall performance of the device, resulting in greater stability and a longer lifespan.

[0025] In the amplifier system configuration described above, a portion of the emitted coupled beam is extracted from the beam coupling means at the output of the final interference light amplifier stage and sent out as the output radiation of the laser device of the present invention, while the remaining portion of the emitted coupled beam circulates within the resonant structure to generate laser oscillation. Thus, in this design, the beam coupling means also simultaneously performs the role of an output coupler means for the resonant structure. For example, a portion of the beam emitted from the amplifier system and sent out as output laser radiation is the lost beam of the beam coupling means, and the majority of the coupled beam emitted from the amplifier system is reintroduced there and amplified again.

[0026] In an alternative embodiment, the output coupler means is obtained as a beam splitting means positioned at the end of the optical return path of the interference beam and configured at the input of an amplifier system (of the gain means) to extract a minimum portion of the beam from the beam circulating within the resonant structure and deliver it as output laser radiation.

[0027] The beam portion that contributes to the radiation output of the laser device, i.e., the circulating power P b Laser output P based on out The percentage of optical power extracted is related to the circulating power via the reflectivity parameter R of the output coupler means. Depending on the position of the output coupler means within the resonant structure, it is as follows: P out =R·P b Conversely, the reverse is also true. P out =(1-R)·P b

[0028] Typically, there exists an optimal value for R that depends on the characteristics of the resonant structure, and it specifically refers to the loss the beam experiences during propagation.

[0029] The constituent subject of this invention enables the achievement of steady-state equilibrium conditions between loss (output of the laser device), gain, and interference between recombined beams in each interferometer configuration. The splitting ratio of the beam splitting means and the optical lengths of the individual amplified and unamplified propagation branches of each interferometer configuration are selected and controlled to optimize the overall performance of the device, including spectral separation between the maximum interference values ​​between the recombined beams. In fact, under real-world configurations and operating conditions, the optical path difference between the two branches is not zero, resulting in an interference spectrum between the combined beams, and the power of the combined beam corresponds to the average value between the maximum and minimum power values ​​of the interfering beams. The spectral separation between two maximum or two minimum interference values ​​depends on the difference in the optical paths through which the two interfering beams travel.

[0030] Theoretically, by stabilizing the resonant structure, i.e., by making the phase difference between the beam guided via the amplified branch and the beam guided via the unamplified propagation branch zero, the performance of a single interference amplification configuration is equivalent to (or exceeds) that of a standard non-interference laser diode, i.e., an external cavity semiconductor laser diode. In fact, compared to an external cavity semiconductor laser diode, it is possible to obtain a power reduction in the gain means. This is because it operates in a saturated state, and at lower incident light power operating conditions, the gain becomes greater.

[0031] Simulation results performed by the inventors showed that the power output from the laser device according to the present invention, which has two gain interference stages, is greater than the (incoherent) sum of the powers of the two individual laser devices, and more generally, the power output from the laser device according to the present invention with n interference gain stages is greater than the (incoherent) sum of the powers of the n individual laser devices.

[0032] Conveniently, the proposed design eliminates the need to perform complex techniques for controlling the phase of each laser emission device, making it possible to obtain a coherent beam with high optical power. However, employing frequency stabilization techniques for real-time and active control of the phase acquired by the beam during propagation, for example by controlling the phase within the gain means, generating delay lines, or utilizing Pound-Drever-Hall stabilization (where a single-wavelength oscillation corresponding to the maximum interference between the amplified and unamplified beams is forced within the resonant structure), would enable further increases in power and a narrower emission bandwidth. [Brief explanation of the drawing]

[0033] Further features and advantages of the present invention will be presented in more detail below in the detailed description of its embodiments, which are provided as non-limiting examples, with reference to the accompanying drawings.

[0034] [Figure 1] This is a schematic diagram of the laser device according to the present invention. [Figure 2] This is a first schematic embodiment of the laser device according to the present invention, and in a free-space embodiment, it has a single interference light amplification arrangement. [Figure 3] Figure 2 shows a modified embodiment of the laser device. [Figure 4] Figure 3 is a simulation diagram of the laser device's behavior. [Figure 5] Figure 3 shows a modified embodiment of the laser apparatus, which features two cascaded interference light amplification configurations. [Figure 6] This is a second schematic embodiment of the laser device according to the present invention, and in the free-space embodiment, it has a single interference light amplification arrangement. [Figure 7] Figure 6 is a simulation diagram of the laser device's behavior. [Figure 8] Figure 6 shows a second embodiment of the laser device, which includes two cascaded interference optical amplification configurations. [Figure 9]Shows a third embodiment of a laser device according to the present invention, having a single interference light amplification arrangement in a free space embodiment. [Figure 10] Shows a third embodiment of the laser device of Fig. 9, comprising a plurality of cascaded interference light amplification arrangements.

Embodiments for Carrying Out the Invention

[0035] Fig. 1 schematically shows the essential aspects of a laser device according to the present invention, generally designated by the reference numeral 10. It includes an amplifier system 12 for an incident light beam B i and an optical return path 14 for the light beam B emerging from the amplifier system 12, which is configured to carry the light beam B o as an incident light beam B to the input of the amplifier system 12, an optical return path 14 that forms an optical resonance structure together with the amplifier system 12, and means 16 for outputting coherent light radiation from the laser device, configured to extract a portion of the beam emerging from the amplifier system or, alternatively (represented by the dashed line), a portion of the incident beam incident on the amplifier system, and to emit the beam portion as an output laser radiation B o i L L L L

[0036] The amplifier system 12 comprises a single interference light amplification arrangement 20 or a plurality of interference light amplification arrangements 20 connected in series or in cascade, as schematically shown within the block 12. Each interference light amplification arrangement 20 includes input beam splitting means configured to spatially split an incident light beam into a first beam portion B1 and a second beam portion B2. Downstream thereof, the first beam portion B1 is guided into an amplification arm 20a and the second beam portion B2 is guided into a non-amplified propagation arm 20b. Beam combining means, different from the input beam splitting means, is configured to combine a first portion of the amplified beam coming from the amplification arm 20a and a second portion of the beam propagated without amplification coming from the propagation arm 20b of each interference light amplification arrangement 20, thus substantially forming a Mach-Zehnder interference arrangement, and the combining means of the last optical interference amplification arrangement in series is the light beam B emerging from the amplifier system 12o It forms.

[0037] The amplification arm 20a includes an active region or gain region G that can emit photons coherent with the first portion of the beam B1 by stimulated emission following excitation, for example, using optical or electrical pumping.

[0038] In the currently preferred embodiment, the active region includes a semiconductor material, and an electrical excitation system is provided therein to alter the thermodynamic equilibrium of the charge carrier population confined therein, thereby determining the inversion conditions of the charge carrier population and consequently performing radioactive recombination.

[0039] In alternative embodiments, the active region may include other materials capable of supporting the stimulated emission of photons following optical or electrical excitation.

[0040] Figure 2 shows a first schematic embodiment of the laser device according to the present invention, which has a single interference light amplification arrangement 20 in a free-space embodiment.

[0041] The interference light amplification configuration 20 is for incident beam B i The system includes an input means BS that divides the beam into a first beam portion B1 and a second beam portion B2, and an output coupling means BC of the first beam portion B1 and the second beam portion B2 which are amplified in the active gain region G. o The light is returned to the input of the same interference optical amplification arrangement 20 via an optical return path 14 that forms an optical resonant ring structure including, in a non-limiting example, four planar mirrors M1 to M4.

[0042] In embodiments where the active gain region G of the amplification branch is formed by an optical semiconductor amplifier, it is convenient to associate the input beam coupling stage 22 and the output beam collimation stage 24, which can be obtained by the following configuration. A pair of aspherical lenses. The first lens is configured to focus the beam incident on the amplification region, and the second lens is configured to collimate the beam exiting the amplification region. A pair of aspherical lenses and a pair of cylindrical lenses for circularizing the beam. The first lenses are configured to focus and circularize the beam incident on the amplification region, while the second lenses are configured to circularize and collimate the beam leaving the amplification region. A pair of spherical lenses and a pair of anamorphic prisms. Each is incident on and exits the amplification region. A pair of cylindrical lenses comprising an aspherical lens for focusing a beam incident on the amplification region and collimating the beam exiting the amplification region to create a circular beam. A pair of microlenses. Each focuses the beam entering the amplification region and collimates the beam leaving the amplification region. A microlens that focuses the beam incident on the amplification region, and a pair of microlenses that collimate the beam exiting the amplification region in both the slow and fast axes.

[0043] The propagation arm 20b may include one or more reflective or refractive optical elements (not shown) to control the optical length of the propagation path and control the spatial shape of the beam.

[0044] The coupling means BC at the output of the interference amplification arrangement 20 further connects to the beam B emitted from the arrangement 20. o By extracting a portion of the beam as the loss beam of the coupling means, the laser device (B L ) forms an output means 16 for coherent light emission.

[0045] Figure 3 shows a modified embodiment of the laser apparatus in Figure 2. The return optical path 14 comprises four planar mirrors M1 to M4 and two curved mirrors M5 and M6 for bending and shaping the beam.

[0046] The figure also shows an optical isolator 26 located downstream of the active region G, configured to allow propagation of the first portion of the amplified beam in a single predetermined direction. The isolator 26 may be present in any other embodiment described and may be placed at any point in the resonant structure. However, since the gain means G exits from both directions, for the sake of simplifying alignment, it is convenient to place the isolator at the output of the active amplification region.

[0047] Figure 4 is a simulation diagram of the behavior of the laser apparatus in Figure 3, showing its output power as a function of the spectral window with respect to the origin of the graph. In detail, the graph shows the result resulting from interference between two beams (amplified and unperturbed). The interference fringe is due to interference between the first beam portion B1, amplified in the active gain region G of arm 20a, and the second beam portion B2, propagating unamplified within arm 20b. The spacing between the fringes depends on the optical path. The dashed line shows the average power, and the dotted line shows the maximum power that can be extracted from a resonant structure of the same dimensions and without interference configuration of propagation branching.

[0048] At maximum interference, the device of the present invention exhibits better performance than a standard laser diode without interference configuration. However, considering the difficulty in balancing the interference configuration, i.e., the impossibility of making the optical paths of the two branches equal, the resulting output power is the average value shown in the graph.

[0049] Figure 5 shows a modified embodiment of the laser apparatus in Figure 3, in which two cascaded interference amplification configurations 20, 20 are connected by a beam splitting means BS', which operates both the recombination of the beam of the upstream interference amplification configuration 20 and the separation of the beam of the downstream interference amplification configuration 20'. In this modified embodiment, the difference in optical lengths of the amplification arms and propagation arms 20a, 20b (20a', 20b') can be minimized, or it is possible to employ interference amplification configurations in which such optical lengths are equivalent.

[0050] Figure 6 shows a second schematic embodiment of the laser device according to the present invention, which, in a free-space embodiment, has a single interference optical amplification arrangement. It shows a more compact structure, where the beam splitting means BS and beam coupling means BC (different from the beam splitting means BS) are connected to the incident beam B i Input path and output beam B o The output path is substantially aligned with the output path. Interference control is lost between the first beam portion B1, which is amplified in the active gain region G of arm 20a, and the second beam portion B2, which is propagated without amplification in arm 20b, and the difference in optical length between the two arms 20a and 20b is significant.

[0051] Figure 7 is a simulation of the behavior of the laser apparatus in Figure 6, showing its output power as a function of the spectral window with respect to the origin of the graph. In detail, the graph shows the results resulting from interference between two beams (amplified and unperturbed). The fringe is due to interference between the amplified and unperturbed beams. The interference fringe between the first beam portion B1, amplified in the active gain region G of arm 20a, and the second beam portion B2, propagating unamplified within arm 20b, is optical path dependent and differs from the fringe spacing in the graph of Figure 4 due to the different optical paths. A narrower fringe corresponds to a larger difference in the optical path through which the beams travel. The dashed line shows the average power, and the dotted line shows the maximum power that can be extracted from a resonant structure of the same dimensions and without interference configuration of propagation branching.

[0052] Figure 8 shows a second embodiment of the laser apparatus of Figure 6, which features two cascaded interferometric amplification arrangements. Compared to the configuration of Figure 5, this configuration is more compact in the free-space embodiment.

[0053] Figure 9 shows a third embodiment of the laser device according to the present invention, which has a single interference optical amplification configuration in a free-space embodiment.

[0054] Unlike the first and second embodiments, the means 16 for outputting coherent light radiation from the laser device is configured to extract a portion of the beam guided along an optical return path and incident on the amplifier system, and to emit the beam portion as laser radiation at the output.

[0055] Figure 10 shows multiple interference optical amplification arrangements in cascade connection 20, 20', 20 n Figure 9 shows the configuration with the following: The first interference optical amplification arrangement includes beam splitting means BS along the amplification arm. i Except for the intervention of the beam splitting means BS, each intermediate interference amplification configuration is substantially similar to the interference amplification configuration characterizing the above-described embodiment, and is configured to extract a smaller portion of the amplified beam and guide it toward the amplification arm of a subsequent downstream interference amplification configuration, separate from the larger portion of the amplified beam guided toward the coupling means BC. i It has a beam splitting means BS which acts exclusively on the beam of the amplification arm 20a of the preceding interference stage and does not act on the recombined beam of the preceding interference stage. The coupling means BC of each interference optical amplification arrangement is a beam splitting means BS i Unlike the previous configuration, the remaining beam portion B1' (which is not transmitted to the downstream amplification arm) amplified in the active gain region G and the beam portion B2 propagating without amplification are combined and passed to the next stage. The coupling means BC of each interference amplification configuration may have a relative loss beam that is conveniently guided toward an optical beam detection means D (e.g., a photodiode) configured to monitor the intensity and phase of the beam in the intermediate amplification chain.

[0056] Optically coupled beam B emitted from the series of interferometric optical amplification arrangements in a cascaded amplification system. o The current is returned to the input of the first interference optical amplification configuration of the amplification system via the optical return path 14, which forms an optical ring resonant structure.

[0057] The laser apparatus according to the present invention offers various advantages over solutions provided by the latest technologies. Regarding currently employed incoherent beam coupling techniques, the described apparatus demonstrates the advantages of coherent beam coupling techniques. Regarding wavelength beam coupling techniques, it enables increased power while maintaining the spectral quality of the laser. Regarding coherent beam coupling architectures, it avoids the use of active real-time phase control algorithms for each laser light-emitting device, providing a robust tool that facilitates manufacturing and industrial adoption.

[0058] Furthermore, the implementation of a single resonant structure outside of all amplification stages offers the possibility of directly controlling the spatial shape of the beam within the cavity.

[0059] From a theoretical standpoint, the only constraint on the number of interference amplification configurations in a cascade is given by the gain saturation law of a single optical amplifier with amplification branches.

[0060] It should be noted that the embodiments proposed for the present invention in the foregoing description are purely non-limiting examples of the present invention. Those skilled in the art will readily be able to implement the present invention in various embodiments that are thus covered by this patent without departing from the principles described herein.

[0061] This is especially true with respect to the possibility of configuring beam splitting and coupling means, gain means and resonant structures according to methods or configurations different from those described or referenced above. For example, while an interference amplification arrangement is shown comprising an amplification arm positioned along the transmission direction of the incident beam in the beam splitting means and a non-amplifying propagation arm positioned along the reflection or coupling direction of the incident beam in the beam splitting means, it is possible to reverse the arrangement of the amplification arm and propagation arm relative to the beam splitting means, provided that the majority of the optical power incident on the beam splitting means is directed toward the non-amplifying propagation branch.

[0062] In free-space embodiments of a device with multiple gaining means, special attention is required for the optical alignment of the components, and more conveniently, the device of the present invention may be obtained by comprising, in part or as a whole, a waveguide optical system including an optical fiber system, a system with a semiconductor integrated optical system, or another platform (e.g., glass).

[0063] Naturally, without bias towards the principles of the present invention, the implementation forms and details of execution may vary extensively with respect to those described and illustrated as purely non-limiting examples, without departing from the scope of protection of the present invention as defined by the appended claims.

Claims

1. A laser device (10) configured to emit coherent optical radiation, comprising: An optical beam amplifier system (12) including a single interferometric optical amplifier arrangement (20) or a plurality of serially connected interferometric optical amplifier arrangements (20, 20', 20n), each of which amplifies an incident optical beam (B ｉ an optical beam amplifier system (12) comprising an input beam splitting means (BS) configured to spatially separate the optical beam (B1) into a first beam portion (B1) and a second beam portion (B2), downstream of which an amplification arm (20a) of the first beam portion (B1) comprising an active gain region (G) capable of emitting photons that are coherent with the first beam portion, and an amplification-free propagation arm (20b) of the second beam portion (B2), which meet at the output of the interferometric optical amplification arrangement (20); beam combining means (BC) different from said input beam splitting means (BS), The first amplified beam portion (B1) and the second beam portion (B2) propagating without amplification in a single interferometric optical amplifier arrangement (20) or in the last interferometric optical amplifier arrangement (20'; 20n) in the series are treated as an optical beam (B) emerging from the amplifier system. ｏ a beam combining means (BC) configured to combine the beams into a The light beam (B) emitted from the amplifier system ｏ a return optical path (14) for the emitted light beam (B ｏ a return optical path (14) comprising optical reflector means (M1-M6) configured to guide the optical fiber 102 to the input of an amplifier system (12) forming an optical ring resonator structure; The beam (B) emitted from the amplifier system (12) ｏ ) and extracting a portion of said beam portion from the laser device (10) radiation (B Ｌ and radiation output means (16) configured to deliver the radiation as A laser device (10) characterized in that the power of a first beam portion (B1) routed to an amplification arm (20a) is less than the power of a second beam portion (B2) routed to a non-amplification propagation arm (20b).

2. the amplification arm (B1) comprises an active gain region (G) of semiconductor material capable of emitting photons coherent with the first beam portion (B1) following the attainment of a population inversion condition of charge carriers confined therein and the resulting radiative recombination, 2. The laser device (10) according to claim 1, wherein the active region (G) is provided with an electrical excitation system configured to modify the thermodynamic balance of a population of charge carriers to determine the inversion conditions of the population.

3. A serial interference optical amplification arrangement (20, 20'; 20, 20', ..., 20 ｎ ) in the input beam splitting means (BS ｉ 3. The laser device (10) of claim 1 or 2, wherein the first beam portion of the preceding interference light amplification arrangement is configured to spatially separate the interfering first beam portion from the second beam portion of the preceding interference light amplification arrangement.

4. A serial interference optical amplification arrangement (20, 20'; 20, 20', ..., 20 ｎ ), each intermediate interferometric optical amplification arrangement has at its input beam splitting means (BS) configured to spatially split only the first beam portion of the preceding interferometric optical amplification arrangement and not to spatially split the recombined beam of the preceding interferometric optical amplification arrangement. ｉ 3. The laser device (10) according to claim 1 or 2, comprising:

5. The beam (B) emitted from the amplifier system (12) is delivered as the output radiation (BL) of the laser device (10). ｏ ) is a first amplified beam portion (B1) and a second beam portion (B2) that propagates without amplification, and is coupled to a light beam (B) emerging from the amplifier system (12). ｏ 5. The laser device (10) according to any one of claims 1 to 4, wherein the loss beam of the beam combining means (BC) is configured to combine the beams into a beam.

6. The output radiation (B Ｌ ) from the amplifier system (12). ｏ 2. The laser device (10) of claim 1, wherein said portion of said optical reflector means (M4) is a lost beam in one of said optical reflector means (M4) of the return optical path (14).

7. 7. The laser device according to claim 1, wherein the amplification arm (20a) comprises optical coupling and collimation means (22, 24) coupled to the active region (G) and includes a pair of refractive optics arranged to collect a first beam portion (B1) incident on the active region (G) and to collimate an amplified beam portion emerging from the active region (G).

8. 8. The laser device (10) according to any one of claims 1 to 7, wherein the non-amplified propagation arm (20b) comprises reflective or refractive optics configured to control the addressing or distribution of the transverse power of the second beam portion (B2).

9. The laser device (10) of claim 1, wherein said optical reflector means (M1-M6) comprises a plurality of total internal reflection reflective optics.

10. The beam (B) exiting the amplifier system (12) ｏ 10. The laser device (10) of claim 1, wherein the return optical path (14) of the laser includes optical elements configured to shape the transverse power distribution of the beam.

11. The laser device (10) of any of claims 1 to 10, wherein the optically resonant structure includes an optical isolator (26) configured to allow propagation of the beam in a single predetermined direction.

12. The laser device (10) according to any one of claims 1 to 11, wherein the optical lengths of the amplification arms (20a) and the amplification-free propagation arms (20b) of each interference light amplification arrangement (20) are equivalent.

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