Surface emitting semiconductor laser system

Abstract

A fiber laser pump module includes one or more laser clusters including a plurality of laser units disposed in a common plane. The plurality of laser units are optically decoupled such that light emitted by one laser unit does not interfere with light of another laser unit. The plurality of laser units includes at least some coherent laser units, each coherent laser unit including a plurality of semiconductor surface emitting laser elements optically coupled to one another such that light emitted by one emitting element interferes with light emitted by the other emitting element. Also included is one or more phase correctors for manipulating light emitted by the plurality of coherent laser units to output a plurality of corrected beams propagating in a single direction and having a far field pattern dominated by a single main lobe. The focusing optical assembly is used for focusing the plurality of correction light beams to a focused light beam. The optical fiber is used for receiving and outputting the focused light beam.

Description

Technical Field

[0001] The present disclosure generally relates to the field of high-power laser sources and, more particularly, to laser diode pump modules for fiber lasers. Background Art

[0002] High-power fiber lasers require optical pumping using fiber-coupled pump modules based on laser diodes, also known as semiconductor lasers. Various pump modules for fiber lasers are described in the prior art and are generally based on edge-emitting semiconductor laser emitters.

[0003] For example, edge emitter-based modules are described in U.S. Patent Nos. 7,773,655, 8,000,360, 7,733,932, 7,764,723, 6,898,222, 8,437,086, 8,427,749, 8,711,894, 6,124,973, and 7,751,458.

[0004] Alternative pump module implementations are disclosed in US Pat. Nos. 8,576,885 and 8,929,407 and utilize a class of surface-emitting semiconductor lasers known as vertical-cavity surface-emitting lasers (VCSELs). Summary of the Invention

[0005] Pump modules based on edge-emitting semiconductor lasers suffer from the complexity of non-planar arrangements of semiconductor laser chips, as shown, for example, in U.S. Patent No. 7,773,655. This non-planar arrangement compromises waste heat removal while increasing volume and weight. Furthermore, the optical architecture of such modules involves a large number of micro-optical elements (primarily lenses and mirrors), each of which requires active optical alignment.

[0006] In contrast, pump modules based on semiconductor lasers or surface-emitting lasers (SELs) in a surface-emitting geometry are largely unaffected by the aforementioned issues, but face additional technical challenges. A common type of SEL is the vertical-cavity surface-emitting laser (VCSEL), in which laser oscillation occurs between multiple epitaxially grown mirrors and the vertical cavity, which is only a few microns long. Consequently, the individual VCSEL sources emit low milliwatts of power, necessitating a large number (thousands) of VCSEL elements to achieve the required multi-watt pump powers, which necessitates a large emitting area. The large emitting area occupied by thousands of individual VCSEL elements and their high divergence pose fundamental problems. The angular divergence of the VCSEL emission is typically greater than 5 degrees, requiring collimation of each element with a lens (typically a microlens) so that the resulting array of collimated beams emitted by the VCSEL array can be focused to a single point and coupled into an optical fiber. However, the addition of multiple collimating lenses, even in the form of a compact microlens array, significantly increases the element spacing within the array and the area occupied by the array. The larger the diameter of each collimating lens, the better the collimation (lower the divergence), but the larger the total area. The combined array beam diameter becomes too large and exceeds the etendue (also expressed as the beam parameter product) of the receiving fiber. In other words, the product of the fiber's acceptance angle and its receiving cross-section (core diameter) limits the product of the combined VCSEL source's emission angle and its combined beam diameter. Therefore, the combined VCSEL's emission area is limited, and so is the maximum achievable power. Expressed in terms of brightness (also called radiance), the brightness of the source can equal or exceed the brightness of the fiber into which it is coupled. This limitation is a fundamental physical property and cannot be overcome by engineering improvements to the VCSEL layout, collimation, or focusing optics.

[0007] In other words, existing VCSELs and their arrays lack sufficient scalability to achieve the high output wattage and low beam parameter product required for fiber laser pumping. Consequently, despite their architectural simplicity and low-cost manufacturability, these current high-power surface-emitting laser diode technologies cannot compete with edge-emitting pump modules.

[0008] Coherent surface emitting laser (coherent SEL) components can potentially provide significantly higher brightness than incoherent SEL components, such as the multiple incoherent VCSEL arrays used in U.S. Patent Nos. 8,576,885 and 8,929,407. Here, the term "coherent" means that a fixed optical phase relationship (or phase) spans all or part of the emitting area. To achieve coherence, multiple individual emitting elements in an SEL can be optically coupled so that the collective lasing of the SEL ensemble occurs predominantly in a single collective mode with a narrow spectral linewidth. The collective mode can be referred to as a "supermode" that spans or interlocks all or most of the individual emitting elements in the SEL. Through optical interference throughout the propagation of the emitted coherent field, the angular divergence of the source can be reduced as more elements are added to the coherent SEL. Therefore, the increase in the coherent source area is offset by the reduction in its collective divergence. Therefore, coherent power scaling can be achieved without increasing the optical etendue or the beam parameter product of the source. The aperture of an extended coherent source scales its brightness as the fourth power of the transmit aperture size D: First, the total power is proportional to the aperture area, i.e., ~D 2 Second, the beam divergence from the aperture is proportional to D -1 , whose solid angle is proportional to D -2 , the total overall brightness scales to D4. When the coherence aperture D is large enough, the fiber laser pump brightness requirement can be met and even exceeded.

[0009] The methods for achieving coherence in SELs (hereinafter also referred to as coherence between SEL emitting elements) vary in the technical field and generally involve placing the multiple emitting elements in close proximity to exert strong optical coupling. These strongly coupled elements can still be distinguished as emitters (e.g., multiple elements of a surface-emitting array) or can be grouped together into a generally periodic structure, such as a photonic crystal or diffraction grating. In the latter case, a single unit cell of a photonic crystal, a period of a grating, or an element of a photonic lattice can be defined as a surface-emitting element.

[0010] Coherent SELs can use multiple photonic crystals (e.g., as disclosed in WO2023110203, U.S. Patent No. 7,009,216, WO2021220276, and U.S. Patent No. 7,535,943). Examples of photonic crystal SELs (PCSELs) include waveguide-integrated PCSELs, topological SELs, and active photonic crystal lattice PCSELs.

[0011] Coherent SELs can also include vertical cavities to operate as multiple coupled VCSEL arrays (e.g., as disclosed in U.S. Patent Nos. 6,507,595, 5,086,430, 6,608,849, 5,903,590, and JP2022043541), where the dominant lasing occurs between the epitaxially grown mirrors, but lateral (in-plane) phase locking is provided by various techniques such as reflectivity modulation, anti-waveguide coupling, and slow-light modes.

[0012] Most coherent SELs rely on strong optical coupling between multiple emitting elements, unit cells, or grating periods to achieve surface emission characterized by a fixed optical phase relationship between them. In most cases, the multiple emitting elements are arranged in a two-dimensional array on the surface of the SEL (e.g., as a 2D array), but one-dimensional SELs (e.g., as a 1D or linear array) have also been reported. The device design generally enhances the output of most of the optical power passing through the top or bottom surface of the SEL. However, prior art coherent SELs are subject to three limitations. The first limitation is the coherence length, expressed as the lateral range of the SEL over which coherence is maintained, which is limited by the laser linewidth and process uniformity. Other effects, such as electrical pumping variations and thermal lensing, may further reduce the degree of coherence. This coherence length limits the power emitted by the aperture to be insufficient for fiber laser pumping. The second limitation is the multi-lobe far-field emission pattern, which is not suitable for fiber coupling. Although each individual lobe or beam in the far field can be very narrow and have a near-diffraction-limited angular divergence, the angular coverage of the overall emission pattern is too broad to satisfy the beam parameter product of the receive fiber. The third limitation is that even if most of the emission is concentrated in the central (on-axis) lobe, significant energy can still be in the multiple parasitic side lobes (sometimes called grating lobes) due to incomplete filling of the SEL's transmit aperture.

[0013] The present disclosure is directed to a high-brightness surface-emitting laser diode module that is advantageously used as a fiber laser pump device, with significant benefits in terms of reduced system complexity, size, weight, assembly time, and cost. Furthermore, the present disclosure is not limited to fiber laser pumping and can encompass numerous other applications where the disclosed high-brightness laser module can provide significant benefits, such as laser cutting, optical marking, material processing, LiDAR (Light Detection and Ranging), pumping of erbium-doped fiber amplifiers (EDFAs) and other erbium-doped gain media, second harmonic generation, and the like.

[0014] According to the presently disclosed subject matter, a laser module (e.g., a fiber laser pump module) is provided. The laser module includes one or more laser clusters. The laser cluster(s) include multiple laser units. The multiple laser units are arranged in a common plane. The multiple laser units are optically decoupled. The optical decoupling causes multiple light waves emitted by one laser unit to not interfere with multiple light waves emitted by another laser unit. The multiple laser units include at least some coherent laser units. Each coherent laser unit includes multiple semiconductor surface-emitting laser elements. The multiple semiconductor surface-emitting laser elements are optically coupled to each other. The optical coupling causes multiple light waves emitted by a surface-emitting element to interfere with multiple light waves emitted by another surface-emitting element. The laser module includes one or more phase correctors configured to receive emitted light from the one or more laser clusters. The phase correctors include at least some optical phase correction elements. The optical phase correction elements are configured to manipulate the light emitted by the at least some coherent laser units to produce interference to output multiple corrected light beams. The multiple correction beams propagate substantially in a single direction and have a far-field pattern that is predominantly formed by a single main lobe. The laser module includes a focusing optical assembly. The focusing optical assembly is disposed downstream of the one or more phase correctors. The focusing optical assembly is configured to focus the multiple correction beams into a focused beam. The laser module includes an optical fiber for receiving and outputting the focused beam. The input end of the optical fiber is disposed within the focal plane of the focusing optical assembly.

[0015] In addition to the above features, a laser module according to the presently disclosed subject matter may optionally include one or more of the following features (i) to (xxxii), in any technically possible combination or permutation:

[0016] i. The plurality of laser units are arranged in a first proximity. The first proximity is at least a predefined threshold to prevent mutual optical proximity coupling. The plurality of surface-emitting elements in each coherent laser unit are arranged in a second proximity. The second proximity is shorter than the predefined threshold to induce mutual optical proximity coupling.

[0017] ii. The predefined threshold is less than 10 times the wavelength emitted by the plurality of surface-emitting elements, wherein the wavelength is defined according to light propagation in free space.

[0018] iii. The predefined threshold is 10 microns.

[0019] iv. The single main lobe carries at least 50% of the optical power carried by the far-field pattern, preferably at least 75%, more preferably at least 90%, even more preferably at least 99%.

[0020] v. The divergence of the plurality of correction beams is at most 3 times the diffraction limit of the laser unit.

[0021] vi. Each laser unit is configured to emit a power of at least 100 mW and a spectral linewidth of less than 1 nm, preferably less than 0.5 nm.

[0022] vii. Includes multiple laser clusters, each laser cluster is formed from a separate semiconductor die and includes one or more laser units.

[0023] viii. The plurality of laser clusters are electrically connected in series, wherein the cathode of one laser cluster is electrically connected to the anode of the next laser cluster.

[0024] ix. All laser units in at least one laser cluster are electrically connected in parallel.

[0025] x. The plurality of surface-emitting elements include any of the following: a photonic crystal, a photonic lattice, an optical grating, a distributed Bragg reflector (DBR), a distributed feedback (DFB) region, an etched region, a metal region, a dielectric region, a regrown semiconductor region, and a reflectivity-modulated region.

[0026] xi. The plurality of surface-emitting elements included in at least one of the at least some coherent laser units are arranged in an array with a period of less than 10 microns.

[0027] xii. The one or more phase correctors are configured to provide amplitude-to-phase conversion for increasing optical power propagating along the single direction.

[0028] xiii. The one or more phase correctors include any one of a phase plate, a phase mask, a phase shift mask, a phase delay plate, a wavefront corrector, a metasurface, a Fourier hologram, a transmission grating, a phase grating, a Dammann grating, and a diffractive optical element.

[0029] xiv. The one or more phase correctors include any of a phase stage, a rod, a block, a slit, a nanorod, a nanoblock, and a nanoslit.

[0030] xv. having an output brightness of at least 2 MW / (sq.cm×srad).

[0031] xvi. The emission wavelengths of the plurality of surface-emitting elements range from 770 nm to 1070 nm, preferably one of 915 nm and 976 nm.

[0032] xvii. One or more first laser clusters configured to emit a plurality of light waves in a first polarization, one or more second laser clusters configured to emit a plurality of light waves in a second polarization, and a polarization-sensitive reflector configured to combine the light emitted by the one or more first laser clusters and the one or more second laser clusters.

[0033] xviii. A dichroic module is included, wherein the dichroic module is configured to block back propagation of a plurality of wavelengths different from the wavelengths emitted by the one or more laser clusters, the dichroic module being positioned between the one or more phase correctors and the focusing optical assembly.

[0034] xix. The dichroic module is tilted relative to the single direction of the plurality of correction beams.

[0035] xx. The apparatus comprises a microlens array disposed between the plurality of laser units and the one or more phase correctors. The microlens array is configured to perform Fourier imaging of a plurality of light waves emitted by at least some of the plurality of laser units. At least some of the microlenses correspond to at least some of the plurality of laser units.

[0036] xxi. A phase corrector is integrated into the laser cluster.

[0037] xxii. The focusing optical assembly includes two cylindrical lenses along different axes.

[0038] xxiii. The focusing optical assembly comprises a single lens.

[0039] xxiv. The light emitted by the plurality of coherent laser units forms a plurality of far-field lobes, preferably four lobes.

[0040] xxv. The plurality of laser units include any one of semiconductor materials of gallium arsenide, aluminum arsenide, aluminum gallium arsenide, gallium indium arsenide, gallium indium arsenide phosphide, indium phosphide, and gallium nitride.

[0041] xxvi. The plurality of laser units include a plurality of tunnel contacts or a plurality of buried tunnel contacts.

[0042] xxvii. The emitted light is emitted from the substrate side of the plurality of laser units.

[0043] xxviii. configured to receive power from a power supply unit configured to supply power to a plurality of edge-emitting laser modules.

[0044] xxix. The current supplied by the power supply unit ranges from 10A to 30A.

[0045] xxx. A first portion of the optical fiber is surrounded by a first packaging medium, and a second portion of the optical fiber is surrounded by a second packaging medium in a ferrule, wherein the first and second packaging media have a refractive index that is close to but higher than the refractive index of the optical fiber.

[0046] xxxi. The refractive index ranges from 1.45 to 1.6.

[0047] Applications that may be beneficially combined with the laser modules disclosed herein include fiber laser pump modules and fiber laser systems.

[0048] In this disclosure, the following terms and their derivatives are to be understood as follows:

[0049] The term "optical power" may refer to the power (energy per time) carried by optical radiation.

[0050] The term "intensity" may refer to the power density (power per area) carried by the optical radiation.

[0051] The term "light waves" may be used to refer to an optical radiation.

[0052] The term "brightness" may refer to the physical quantity of power per area per solid angle. The unit of brightness may be, for example, watts per square centimeter per steradian (W / (cm 2 The term "radiance" may be a synonym for the term "brightness".

[0053] The term "coherence" may refer to the degree of phase correlation between individual emitting elements in a laser array or collection. Coherence determines the degree to which the emitted light waves from different laser elements are in phase with each other and can interfere with each other to produce far-field radiation patterns that are substantially different from those produced by the individual elements in isolation.

[0054] The term "optically coupled" may refer to an arrangement where two or more emitting elements operate in a synchronized manner such that the two elements emit light with a time-invariant phase relationship.

[0055] The term "mutual optical proximity coupling" can refer to the physical or spatial proximity of two or more wave sources, such as light or electromagnetic radiation. When two or more emitting elements are positioned within a distance equivalent to the wavelength of the waves they emit, the electromagnetic fields they generate can interact. This interaction can lead to phase correlations in the emitted waves, affecting the overall coherence of the multiple sources. The term "wavelength" is most commonly interpreted here to refer to the wavelength of the emitted radiation. However, in the case of photonic crystal SELs, optical interactions in the plane of the photonic crystal lattice can occur with very low group velocities of so-called "slow light," as disclosed, for example, in European Patent No. EP3425755 and Japanese Patent Application No. JP2022 / 043541. Due to the extremely low modal effective refractive index associated with in-plane propagation, this "slow light" can have a characteristic wavelength and proximity coupling distance that can be significantly greater (e.g., 20 times longer) than the free-space wavelength of the emitted radiation.

[0056] The term "optically decoupled" or "optically decoupled" means the lack of "mutual optical proximity coupling" as described above but may include coupling or merging (e.g., beam merging) into a common container (e.g., an optical fiber or a phase corrector), wherein this coupling or merging does not produce optical feedback and does not have an effect on the behavior or characteristics of the multiple sources (e.g., multiple laser units or emitting elements), in particular, with respect to their coherence. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to better understand the subject matter disclosed herein and to illustrate how it may be implemented in practice, embodiments will now be described, however by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0058] Figures 1A to 1B A fiber laser pump module according to an embodiment of the present disclosure is schematically shown.

[0059] Figures 2A to 2B Another fiber laser pump module according to an embodiment of the present disclosure is schematically shown.

[0060] Figures 3A to 3B A fiber laser pump module including an amplitude-to-phase converter according to an embodiment of the present disclosure is schematically shown.

[0061] Figures 4A to 4B Schematically illustrates a plurality of fiber laser pump modules including polarization beam combining according to an embodiment of the present disclosure.

[0062] Figures 5A to 5B A laser cluster including a plurality of coherent laser units according to an embodiment of the present disclosure is schematically shown.

[0063] Figures 6A to 6BA laser cluster according to an embodiment of the present disclosure is schematically shown ( Figure 6A ) spatial arrangement and a corresponding mounting base ( Figure 6B ).

[0064] Figure 7 An optical fiber cable coupling assembly according to an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0065] This disclosure describes several specific examples of laser modules that are particularly advantageous for fiber laser pumping but also have numerous applications. In the following detailed description, numerous specific details are provided to provide a thorough understanding of the subject matter. However, those skilled in the art will appreciate that some examples of the subject matter can be practiced without these specific details. In other instances, common methods, procedures, and components have not been described in detail to avoid obscuring the description.

[0066] As used herein, the terms "for example," "such as," "for example," and variations thereof describe non-limiting examples of the subject matter.

[0067] References in the specification to "an example," "some examples," "another example," "another example," "an instance," "some examples," "another example," "another example," "a case," "some cases," "another case," "another case," or variations thereof, indicate that the specifically described features, structures, or characteristics are included in at least one example, but the appearance of the same term does not necessarily refer to the same example. The term "each" should not be understood as meaning only each and every one, but may also mean "at least some" when technically relevant.

[0068] It should be understood that certain features, structures, and / or characteristics disclosed herein, which for clarity are described in separate examples, may also be provided in combination in a single example. Conversely, various features, structures, and / or characteristics disclosed herein, which for brevity are described in a single example, may also be provided separately or in any suitable subcombination.

[0069] Figures 1A to 1B A fiber laser pump module 100 according to an embodiment of the present disclosure is schematically shown. Figure 1A shows a perspective view of the fiber laser pump module 100, and Figure 1B A top (plan) view of the fiber laser pump module 100 is shown.

[0070] The fiber laser pump module 100 may include one or more laser clusters 112. The one or more laser clusters 112 may include one or more surface-emitting laser units disposed on a common surface, such as a base plate 101. The laser units may have their emission surfaces aligned on a common emission plane, for example, at the same height from the base plate 101, which can significantly simplify the optical architecture of the module.

[0071] The base plate 101 can provide both electrical connections and waste heat removal for the one or more laser clusters 112. For example, the base plate 101 can be mounted to a thermoelectric cooler or other cooling device, such as a water-cooled or microchannel cooled carrier.

[0072] Depending on the characteristics of the laser units, such as power and thermal requirements, the laser units can be arranged in many different ways to achieve a high total optical wattage (optical power). For example, such a plurality of laser units can be obtained by a plurality of clusters, each containing several laser units, or each cluster containing only one laser unit, or by a single large cluster containing many laser units.

[0073] In some embodiments, the multiple laser units can be optically decoupled, i.e., the multiple laser units are mutually incoherent. In other words, the multiple light waves emitted by one laser unit may not interfere with the multiple light waves of another laser unit. Optical decoupling can be achieved by separating the multiple laser units by at least several times the wavelength, for example, 10 wavelengths or more, to avoid optical interaction or proximity coupling between adjacent laser units. In other words, the distance between one laser unit and another laser unit can be greater than a predefined threshold (for example, greater than 9 microns in some embodiments). In some embodiments, optical decoupling can be enhanced by structural perturbations between adjacent laser units, such as etching, cutting, sawing, or depositing optically opaque or reflective materials. Thus, the multiple laser units can emit light as multiple independent sources, such that their incoherent combination in the far field results in a total intensity that is substantially equivalent to the sum of the intensities of the multiple individual laser units.

[0074] The multiple laser units may include at least some coherent laser units. Preferably, all laser units may be multiple coherent laser units. In some embodiments, the coherent laser unit may be formed by a coherent semiconductor surface-emitting laser having multiple surface-emitting elements. In other embodiments, the coherent laser unit may be formed by a coherent semiconductor surface-emitting laser array, wherein the multiple surface-emitting elements are formed by individual surface-emitting lasers (SEL). In some embodiments, the SEL may be a VCSEL. In some embodiments, the laser unit may be formed by a vertical-cavity surface-emitting laser (VCSEL) or a VCSEL array.

[0075] The plurality of surface-emitting elements may be optically coupled to one another such that the plurality of light waves emitted by one surface-emitting element interfere with the plurality of light waves emitted by another surface-emitting element. The coherent laser unit may preferably be formed from a coherent semiconductor laser source comprising a plurality of surface-emitting elements optically coupled to one another in proximity. Here, proximity coupling may refer to mutual coupling (e.g., nearest neighbor coupling, evanescent coupling, or diffraction) between the plurality of surface-emitting elements and may be enabled by their physical proximity or spatial proximity. When the plurality of surface-emitting elements are positioned at a distance corresponding to the wavelengths of the plurality of light waves they emit, the plurality of electromagnetic fields they generate may interact. This interaction occurs when the distance from one surface-emitting element to another surface-emitting element may be less than a predefined threshold (e.g., less than 5 microns in some embodiments). This interaction may result in consistent correlation in the phases of the plurality of emitted waves, leading to overall coherence of the coherent laser unit.

[0076] The separation between the plurality of surface-emitting elements and the separation between the plurality of laser units can be summarized as follows: the plurality of laser units can be arranged according to a first proximity, wherein the first proximity is at least a predefined threshold to avoid mutual optical proximity coupling. The plurality of surface-emitting elements, within each coherent laser unit, can be arranged according to a second proximity, wherein the second proximity is shorter than the predefined threshold to induce mutual optical proximity coupling. In some embodiments, the predefined threshold can be less than 10 times the wavelength emitted by the plurality of surface-emitting elements. The wavelength can be defined based on the propagation of light in free space, i.e., not based on the wavelength of "slow light". In some embodiments, the predefined threshold can be 10 micrometers.

[0077] In some embodiments, the plurality of surface-emitting elements may include (or may be formed from) any of the following: a photonic crystal, a photonic lattice, an optical grating, a distributed Bragg reflector (DBR), a distributed feedback (DFB) region, an etched region, a metal region, a dielectric region, a regrown semiconductor region, and / or a reflectivity-modulated region. In some embodiments, the plurality of surface-emitting elements may be arranged in a periodic array with a period less than 10 microns (i.e., may be periodically arrayed). In some embodiments, the surface-emitting elements may be formed from any of the following: a unit cell of a photonic crystal, a period of a grating, and an element of a photonic lattice.

[0078] Because the phase correlation is limited to a single coherent laser unit, the multiple surface-emitting elements of one laser unit can interfere with each other in free space, while they may not interfere with the multiple surface-emitting elements of another laser unit. In some embodiments, the emitted light from each laser unit can form multiple far-field lobes. Preferably, the emitted light forms one or four lobes.

[0079] Examples of laser clusters and laser units that can be used in the fiber laser pump module according to the present disclosure are further described below with reference to Figures 5A to 5B and Figures 6A to 6B discuss.

[0080] The fiber laser pump module 100 may include a phase corrector 120. The phase corrector 120 may be configured to receive emission light from the one or more laser clusters, i.e., emission light from some or all of the plurality of laser units. In some embodiments, the fiber laser pump module 100 may include more than one phase corrector.

[0081] The phase corrector 120 may include at least a plurality of phase correction elements. The plurality of phase correction elements may be configured to manipulate a plurality of light waves emitted by one or more coherent laser units. In some embodiments, each phase correction element may correspond to a coherent laser unit. The plurality of phase correction elements may be configured to manipulate the light emitted by the coherent laser units to generate interference and output a plurality of corrected light beams 190.

[0082] The plurality of correction beams 190 may propagate in substantially a single direction. In some embodiments, the term "substantially" may mean a divergence angle that is not significantly greater than the diffraction limit of the laser unit. In some embodiments, the divergence of the plurality of correction beams 190 may be up to three times the diffraction limit of the laser unit. For reference, the diffraction limit is the minimum physically achievable divergence of a Gaussian beam. The diffraction limit may be given by a full-angle value of 4λ / πD, where λ is the emission wavelength and D may be the beam diameter or its lateral extent.

[0083] The plurality of correction beams may have a far-field pattern predominantly formed by a single main lobe. In some embodiments, the optical power (i.e., the power carried by the optical radiation) of the single main lobe may be at least 50% of the optical power of the far-field pattern. Preferably, the optical power of the single main lobe may be at least 75% of the optical power of the far-field pattern. More preferably, the optical power of the single main lobe may be at least 90% of the optical power of the far-field pattern. Even more preferably, the optical power of the single main lobe may be at least 99% of the optical power of the far-field pattern.

[0084] It is noteworthy that having a single main lobe allows for efficient coupling of the main (on-axis) lobe into the fiber. The coupling of the multiple side lobes can be low or even unnecessary. If the area emission fill factor of the laser unit is high enough, the multiple side lobes can contain very low power. This avoids the need for any additional phase correction.

[0085] It is worth noting that, in general, ray tracing in the near-to-far field transition region (e.g., the Fresnel to Fraunhofer region) may not follow geometric optics. Therefore, the traced ray paths upstream of the plurality of correction beams 190 may not convey complex coherent field propagation.

[0086] The fiber laser pump module 100 may include a focusing optical assembly 140 disposed downstream of the phase corrector. The focusing optical assembly 140 may be configured to focus the multiple corrected beams into a focused beam. The focused beam may be received by an output end of an optical fiber 150. The input end of the optical fiber 150 may be disposed in a focal plane of the focusing optical assembly 140. The optical fiber 150 may output the focused beam. The optical fiber may be mounted on a fiber block 153.

[0087] Optional features of the fiber laser pump module 100 are further described below.

[0088] In some embodiments, the phase corrector 120 can be placed in the near-field region. The phase corrector 120 can provide an appropriate phase delay across the aperture to convert the source fixed phase relationship into a constant (uniform) phase distribution. This uniform phase distribution and near-uniform or Gaussian intensity profile can facilitate coupling into optical fibers.

[0089] In some embodiments, the phase corrector 120 can be placed in the far-field region. The phase corrector 120 can operate as a diffractive optical element, for example, as a Dammann grating. The phase corrector 120 can combine multiple mutually coherent far-field lobes to form the multiple corrected beams 190.

[0090] In some embodiments, the phase corrector 120 can be integrated into the laser cluster 112 or into the laser unit itself. In other words, the phase corrector 120 can be inseparable from the laser cluster 112 or the laser unit without damaging them. For example, during the manufacturing process of the fiber laser pump module 100, the stage of manufacturing the phase corrector 120 can include a vapor deposition technique, in which material can be deposited on the laser cluster 112. Alternatively, the phase corrector 120 can be manufactured by patterning and etching the material of the laser cluster 112 or the material comprising the laser unit. In another example, the phase corrector 120 can be attached to the laser cluster 112, for example, by an adhesive outside the emission area.

[0091] The phase corrector 120 can be made of a transparent material, such as glass or silicon dioxide. The phase corrector 120 can be manufactured using photolithography or nanoimprinting techniques. In some embodiments, the phase corrector 120 can include any of the following features: phase steps, pillars, blocks, slits, nanopillars, nanoblocks, and nanoslits.

[0092] In some embodiments, the phase corrector 120 may include any of the following optical elements: a phase plate, a phase mask, a phase shift mask, a phase delay plate, a wavefront corrector, a metasurface, a Fourier hologram, a transmission grating, a phase grating, a Dammann grating, and / or a diffractive optical element.

[0093] In some embodiments, the phase corrector 120 may be configured to correct only emissions from coherent sources. For example, all of the plurality of phase correction elements may be configured to correct only emissions from a plurality of coherent sources.

[0094] The fiber laser pump module 100 can provide high optical power and high brightness. In some embodiments, the optical power provided by the fiber laser pump module 100 can be at least 30W. In other words, the optical power coupled to the optical fiber 150 can be at least 30 watts (W). In some embodiments, each coherent laser unit can be configured to emit at least 100 milliwatts (mW) of power. In some embodiments, the fiber laser pump module 100 can have a power of at least 2 MW / (sq.cm×srad) (i.e., 2·10 6 W / (cm 2 ×sr))’s output brightness.

[0095] In some embodiments, the fiber laser pump module 100 may have an output brightness of at least 2 MW / sq.cm×srad, and the optical power provided by the fiber laser pump module 100 may be at least 30 W. The optical fiber 150 may have a diameter of 105 μm and a numerical aperture (NA) of 0.22.

[0096] The plurality of semiconductor surface-emitting elements can be configured to emit light comprising a plurality of specific wavelengths. In some embodiments, the emission wavelengths of the plurality of semiconductor surface-emitting elements can range from 770 nanometers (nm) to 1070 nm. Preferably, the emission wavelength of the plurality of semiconductor surface-emitting elements can be any one of 915 nm and 976 nm.

[0097] In some embodiments, the plurality of laser units can be configured to provide specific wavelengths. In other words, the wavelength range (i.e., the linewidth) emitted by the plurality of laser units can be narrower than a predefined threshold. In some embodiments, the linewidth of the plurality of laser units can be less than 1 nanometer. Preferably, the linewidth of the plurality of laser units can be less than 0.5 nanometers.

[0098] In some embodiments, the plurality of laser units may include any one of semiconductor materials of gallium arsenide, aluminum arsenide, aluminum gallium arsenide, gallium indium arsenide, gallium indium arsenide phosphide, indium phosphide, and / or gallium nitride.

[0099] In some embodiments, the plurality of laser units may include a plurality of tunnel contacts and / or a plurality of buried tunnel contacts.

[0100] In some embodiments, the plurality of laser units may be configured to emit light from the semiconductor substrate side. This configuration may be referred to as "bottom emission."

[0101] In some embodiments, the fiber laser pump module 100 can be configured to receive power from a power supply unit configured to supply power to a plurality of edge-emitting laser modules. This can provide a simplification advantage when replacing edge-emitting laser pump modules with the fiber laser pump module 100. In some embodiments, the current of the power supply unit can range from 10 amps (A) to 30 amps (A).

[0102] In some embodiments, the fiber laser pump module 100 may include a lens disposed between the laser unit and the phase corrector 120. The lens may be configured to Fourier image the light emitted from the laser unit. In some embodiments, the lens may include a Fourier lens. In some embodiments, the lens may be configured to Fourier image the light emitted from multiple laser units, or the light emitted from the entire laser cluster 112, or the light emitted from multiple laser clusters. In some embodiments, the lens may include a microlens array, where some of the microlenses may correspond to some of the multiple laser units.

[0103] In some embodiments, the focusing optical component 140 may include two cylindrical lenses along different axes. In other embodiments, the focusing optical component 140 may be composed of a single lens.

[0104] In some embodiments, the fiber laser pump module 100 may include multiple laser clusters. Each laser cluster may be formed on a separate semiconductor die. In some embodiments, each laser cluster may include one or more laser units.

[0105] In some embodiments, the multiple laser clusters may be electrically connected in series. In other words, the cathode of one laser cluster may be electrically connected to the anode of another laser cluster. In other words, the anode of one laser cluster may be electrically connected to the cathode of another laser cluster. In some embodiments, all laser units in at least one laser cluster may be electrically connected in parallel. In other words, the cathodes of all laser units (in at least one laser cluster) may be connected to one another, and their anodes may be connected to one another.

[0106] Figures 2A to 2B A fiber laser pump module 200 according to an embodiment of the present disclosure is schematically shown. Figure 2A shows a perspective view of the fiber laser pump module 200, and Figure 2B A side view of the fiber laser pump module 200 is shown.

[0107] The fiber laser pump module 200 may include one or more laser clusters 212 . The one or more laser clusters 212 may include a plurality of laser units disposed on a common emitting surface, such as a base plate 201 .

[0108] The multiple laser units may be optically decoupled as described above with respect to Figures 1A to 1B A fiber laser pump module 100 is schematically shown and illustrated.

[0109] The plurality of laser units may include at least some coherent laser units. The plurality of coherent laser units may include a plurality of optically coupleable semiconductor surface emitting elements, as described above with respect to the fiber laser pump module 100.

[0110] The fiber laser pump module 200 may include two phase correctors 220a and 220b. The two phase correctors 220a and 220b may function as an amplitude-to-phase converter 230. The amplitude-to-phase converter 230 may be configured to provide amplitude-to-phase conversion to increase optical power propagating in a single direction. In some embodiments, the amplitude-to-phase converter 230 may include multiple lenses. In some embodiments, the amplitude-to-phase converter 230 may be configured to increase the density of optical power propagating in the single direction.

[0111] In some embodiments, the fiber laser pump module 200 may include an amplitude-to-phase converter (APC) distinct from the plurality of phase correctors. In other words, the APC 230 may be configured to operate in conjunction with one or more phase correctors to provide a plurality of corrected beams 290 that are substantially uniform in phase and have a substantially Gaussian intensity profile, which facilitates fiber coupling.

[0112] The phase correctors 220a, 220b may have an input plane that is substantially parallel to the common emission plane and configured to receive light emitted from one or more laser clusters, ie, light emitted from one or more laser units.

[0113] The phase correctors 220a and 220b may include at least a plurality of phase correction elements. The plurality of phase correction elements may be configured to manipulate light emitted by the at least a plurality of coherent laser units. Each phase correction element may correspond to one or more coherent laser units. The plurality of phase correction elements may be configured to generate a specific interference pattern to output at least a plurality of individual corrected light beams 290.

[0114] The plurality of correction beams 290 may propagate substantially in a single direction, as explained above with reference to the plurality of correction beams 190 (ie, with respect to the fiber laser pump module 100).

[0115] It is worth noting that, in general, ray tracing in the near-to-far field transition region (e.g., the Fresnel to Fraunhofer region) may not follow geometric optics. Thus, the traced ray paths upstream of the plurality of correction beams 290 may not convey complex coherent field propagation.

[0116] The fiber laser pump module 200 may include a focusing optical assembly 240 disposed downstream of the phase corrector. The focusing optical assembly 240 may be configured to focus at least some of the corrected beam onto an input portion of an optical fiber 250, with the optical fiber input portion disposed at a focal plane of the focusing optical assembly 240. The optical fiber 250 may be mounted on a fiber block 253.

[0117] In some embodiments, the focusing optics 240 may include a rectangular lens to conform to the shape of the emission area of the laser cluster 212. In some embodiments, the focusing optics 240 may include two cylindrical lenses, each oriented along a different axis. If the multiple correction beams 290 may have different characteristics or sizes along these axes, the two cylindrical lenses may provide high power coupling efficiency for the multiple correction beams 290 into the optical fiber 250.

[0118] The fiber laser pump module 200 may include a dichroism module 260 (i.e., a wavelength-selective reflector). The dichroism module 260 may be configured to block counter-propagating light waves, which may have wavelengths different from the wavelengths emitted by the plurality of laser units. The dichroism module 260 may protect the laser cluster 212 from counter-propagating power that may arrive from an external source (e.g., a fiber laser) through the optical fiber 250. The dichroism module 260 may be positioned between the plurality of phase correctors 220a, 220b and the focusing optics assembly 240.

[0119] The dichroic module 260 may be a transparent optical blank having a dielectric coating that is highly reflective at the fiber laser wavelength (eg, 1064 nm) but highly transmissive at the laser unit wavelength (eg, 976 nm).

[0120] In some embodiments, the dichroic module 260 can be tilted relative to the single direction 290 of the plurality of correction beams. In other words, the normal vector on the surface of the dichroic module 260 can be non-parallel to the Poynting vectors of the plurality of correction beams 290. The dichroic module 260 can be tilted to avoid on-axis back reflections of the incident fiber laser power.

[0121] For the sake of brevity, optional features associated with the fiber laser pump module 200 that also appear in the embodiment of FIG. 1 and have been described above will not be repeated.

[0122] Figure 3A A fiber laser pump module 300 according to an embodiment of the present disclosure is schematically shown.

[0123] The fiber laser pump module 300 may include one or more laser clusters 312. The one or more laser clusters 312 may include multiple laser units disposed on a common emitting surface, such as a base plate 301.

[0124] The multiple laser units may be optically decoupled as described above with respect to the fiber laser pump module 100 .

[0125] The plurality of laser units may include at least some coherent laser units. The plurality of coherent laser units may include a plurality of optically coupleable semiconductor surface emitting elements, as described above with respect to the fiber laser pump module 100.

[0126] The fiber laser pump module 300 may include a first phase corrector 320a and a second phase corrector 320b. The phase correctors 320a and 320b may have an input plane substantially parallel to the common emission plane and configured to receive emission light from the one or more laser clusters, i.e., emission light from one or more laser units.

[0127] The phase correctors 320a, 320b may include at least a plurality of phase correction elements that may be configured to generate a specific interference pattern to output at least a plurality of individual corrected beams 390.

[0128] The plurality of correction beams 390 may propagate substantially in a single direction, as described above with reference to the plurality of correction beams 190. It is noteworthy that, in general, ray tracing in the near-to-far field transition region (e.g., the Fresnel to Fraunhofer region) may not follow geometric optics. Therefore, the traced ray paths upstream of the plurality of correction beams 390 may not convey complex coherent field propagation.

[0129] The fiber laser pump module 300 may include an amplitude phase corrector 330. The amplitude phase corrector 330 may include two phase correctors 320a and 320b, a first lens 331a, and a second lens 331b. The first lens 331a may be positioned upstream of the first phase corrector 320a. The second lens 331b may be positioned between the first and second phase correctors 320a and 320b. The first and second lenses 331a and 331b may include a plurality of microlens elements.

[0130] The amplitude-to-phase converter 330 may be configured to provide amplitude-to-phase conversion for increasing optical power propagating in a single direction. The amplitude-to-phase converter 330 may further be configured to increase the density of optical power propagating in a single direction.

[0131] The amplitude-to-phase converter 330 can receive coherent radiation from one or more coherent laser units in the one or more laser clusters 312. The first lens 331a can Fourier image the received coherent radiation to the first phase corrector 320a. The first phase corrector 320a can apply a first phase transform to the received coherent radiation to obtain phase-transformed coherent radiation. The second lens 331b can Fourier image the phase-transformed coherent radiation to the second phase corrector 320b. The function of the second lens 331b can be described as inverting the Fourier imaging performed by the first lens 331a, but with any amplitude and / or phase changes caused by the transform applied by the first phase corrector 320a.

[0132] The second lens 331b may output light with residual phase non-uniformity. The residual phase non-uniformity may be corrected by the second phase corrector 320b. The second phase corrector 320b may apply a second phase transformation to output the plurality of corrected light beams 390.

[0133] The plurality of correction beams 390 may have a near-Gaussian intensity profile and a substantially uniform phase profile. High efficiency coupling into the optical fiber may be achieved if the plurality of correction beams 390 have only slight intensity and phase deviations from the plurality of ideal profiles 392. The divergence may be no greater than three times the diffraction limit.

[0134] In some embodiments, more Fourier imaging stages and more phase correctors may be employed to improve the characteristics of the plurality of corrected beams 390 .

[0135] The lenses 331a and 331b can be selected to collect radiation across the lateral extent of the one or more laser clusters 312. In some embodiments, the lenses 331a and 331b can be fabricated as a monolithic microlens array. The plurality of microlenses can correspond to the plurality of coherent laser units in the one or more laser clusters 312. In some embodiments, a third phase corrector can be integrated with the plurality of laser units to limit the divergence of the emitted radiation.

[0136] The fiber laser pump module 300 may include a focusing optical assembly (not shown) disposed downstream of the phase corrector. The focusing optical assembly may be configured to focus the plurality of correction beams 390 onto an input end of an optical fiber.

[0137] For the sake of brevity, optional features associated with the fiber laser pump module 300 that also appear in the embodiments of Figures 1 and 2 and have been described above will not be repeated.

[0138] Figure 3BA fiber laser pump module 3300 according to an embodiment of the present disclosure is schematically shown. The fiber laser pump module 3300 may be a variant of the fiber laser pump module 300 .

[0139] The fiber laser pump module 3300 may include an amplitude-to-phase converter 3330. The amplitude-to-phase converter 3330 may include two phase correctors 3320a and 3320b, a first lens 3331a, and a second lens 3331b. The first lens 3331a may be positioned upstream of the first phase corrector 3320a. The second lens 3331b may be positioned between the first phase corrector 3320a and the second phase corrector 3320b. In some embodiments, the first lens 3331a and / or the second lens 3331b may include a plurality of microlens elements.

[0140] The second lens 3331b may include a Fourier lens. The Fourier lens may be a single lens or an array of lens elements. The second lens 3331b may have fewer lens elements than the first lens 331b of the fiber laser pump module 300.

[0141] Having a large lens with a large focal length can benefit the fiber laser pump module 3300 by improving Fourier imaging and by reducing aberrations. Such advantages can require that the multiple coherent laser units can be identical and can require substantially identical phase corrections by the second phase corrector 3320b.

[0142] In some embodiments, if the first phase corrector 3320a is integrated with the multiple laser units in one or more laser clusters 3312 (e.g., directly defined on the emission surface), the first lens 3331a may be unnecessary. The amplitude-to-phase converter 3330 may include only one lens (the second lens 3331b) followed by a single phase corrector (the second phase corrector 3320b).

[0143] For the sake of brevity, at least some details regarding optional features and regarding elements downstream of the phase corrector 3320b that are similar to the elements downstream of the phase corrector 220b described above with reference to Figures 1 and 2 are not repeated.

[0144] The various APC embodiments given above can be selected to suit the characteristics of a particular plurality of laser units, such as area fill factor and lateral extent, to select from a variety of ideal profiles (e.g., Figure 3A The ideal profile 392 shown results in multiple corrected beams with minimal intensity and phase deviation.

[0145] Figures 4A to 4BA fiber laser pump module 400 including beam combining is schematically shown according to an embodiment of the present disclosure. Figure 4A shows a perspective view of the fiber laser pump module 400, and Figure 4B A top view of the fiber laser pump module 400 is shown.

[0146] The fiber laser pump module 400 can include one or more first laser clusters 412a and one or more second laser clusters 412b. The one or more first laser clusters 412a can be configured to emit a plurality of light waves with a first polarization. The one or more second laser clusters 412b can be configured to emit a plurality of light waves with a second polarization. In some embodiments, the first polarization can be orthogonal to the second polarization. For example, the first polarization can be linearly polarized along the x-axis, and the second polarization can be linearly polarized along the y-axis. It is worth noting that upstream of the polarization-sensitive reflector 470 (described in further detail below), the z-axis can be defined as the direction of light propagation (i.e., according to the Poynting vector).

[0147] Each of the one or more first laser clusters 412a and the one or more second laser clusters 412b may include multiple laser units. In each of the multiple laser clusters 412a, 412b, the multiple laser units may be disposed on a (corresponding) common surface, such as the base plates 401a, 401b.

[0148] In each of the plurality of laser clusters 412a, 412b, the plurality of laser units may be optically decoupled, as described above with respect to the fiber laser pump module 100.

[0149] In each of the plurality of laser clusters 412a, 412b, the plurality of laser units may include at least some coherent laser units. The plurality of coherent laser units may include a plurality of optically coupleable semiconductor surface emitters, as described above with respect to the fiber laser pump module 100.

[0150] The fiber laser pump module 400 may include one or more first phase correctors and one or more second phase correctors. The one or more first phase correctors may correspond to the one or more first laser clusters 412a, and the one or more second phase correctors may correspond to the one or more second laser clusters 412b. Each of the plurality of phase correctors may have an input plane substantially parallel to the common emission plane and configured to receive emission light from the plurality of laser units.

[0151] Each of the plurality of phase correctors may include at least a number of phase correction elements. The plurality of phase correction elements may be configured to manipulate the plurality of optical phases of radiation emitted by one or more coherent laser units. In some embodiments, each phase correction element may correspond to a coherent laser unit. The plurality of phase correction elements may be configured to manipulate the light emitted by the coherent laser units to produce a specific interference pattern, thereby outputting a plurality of corrected light beams.

[0152] The plurality of correction beams may propagate substantially in a single direction. In some embodiments, the term "substantially" may mean a divergence angle that is not significantly greater than the diffraction limit of the laser unit.

[0153] The plurality of correction beams may have a far-field pattern dominated by a single main lobe. In some embodiments, the optical power of the single main lobe (i.e., the power carried by the optical radiation) may be at least 50% of the optical power contained in (i.e., carried by) the far-field pattern.

[0154] It is worth noting that, in general, ray tracing in the near-to-far field transition region (e.g., the Fresnel to Fraunhofer region) may not follow geometric optics. Therefore, the traced ray paths upstream of the multiple correction beams may not convey complex coherent field propagation.

[0155] In some embodiments, the laser pump module 400 may include one or more amplitude-to-phase converters. The one or more amplitude-to-phase converters may correspond only to the one or more first laser clusters 412a, may correspond only to the one or more second laser clusters 412b, or may correspond to both the first and second laser clusters 412a and 412b. The one or more amplitude-to-phase converters may be as described above with respect to Figures 2A to 3B For example, the laser pump module 400 may include a first amplitude-to-phase converter 430a corresponding to the first laser cluster 412a and a second amplitude-to-phase converter 430b corresponding to the second laser cluster 412b. The first amplitude-to-phase converter 430a may include the first one or more phase correctors, and the second amplitude-to-phase converter 430b may include the second one or more phase correctors.

[0156] The fiber laser pump module 400 can include a polarization-sensitive reflector 470. The polarization-sensitive reflector 470 can be configured to combine the light emitted by the one or more first laser clusters 412a and the one or more second laser clusters 412b. Thus, the polarization-sensitive reflector 470 can provide combined light 491. For example, the polarization-sensitive reflector 470 can be a beam splitter. The beam splitter can be configured to have a high reflectivity for polarization along the y-axis and a high transmittance for polarization along the x-axis. In some embodiments, the polarization-sensitive reflector 470 can be based on the principle of total internal reflection or the Brewster angle.

[0157] In some embodiments, the polarization-sensitive reflector 470 may not include a polarization rotator, such as a wave plate. Not having a polarization rotator may have the advantage of reducing manufacturing costs.

[0158] The fiber laser pump module 400 can include a focusing optical assembly 440 disposed downstream of the polarization-sensitive reflector 470 . The focusing optical assembly 440 can be configured to focus the combined light 491 (having multiple corrected beams) to an input of an optical fiber 450 .

[0159] In some embodiments, the optical fiber 450 may be mounted on a fiber optic block 453 .

[0160] The combined light 491 can have mixed polarizations. The optical fiber 450 can be multimode and non-polarization-maintaining. Therefore, the efficiency of coupling light (the combined light 491) into the optical fiber can be unaffected. Thus, according to the present disclosure, the brightness of the light provided by the fiber laser pump module can be doubled by using polarization beam combining. Using polarization beam combining can double the provided optical power, but the light-emitting area of the focusing optical assembly 440 remains unchanged.

[0161] The polarization of the plurality of laser clusters can be determined by introducing asymmetry in the lateral structure of the plurality of laser units and / or the lateral structure of their surface-emitting elements, for example, by imparting a rectangular or elliptical shape. In some embodiments, the optical coupling among the plurality of coherent laser units can be configured to selectively enhance one polarization over another.

[0162] In some embodiments, the one or more laser clusters 412a, 412b may be disposed on a single surface. The one or more laser clusters 412a, 412b may emit light in the same direction. A reflective element (e.g., a mirror or prism) may redirect light provided by one of the plurality of laser clusters by 90° toward the polarization-sensitive reflector 470.

[0163] In some embodiments, the one or more laser clusters 412a, 412b may be identical. The different polarizations of each laser cluster may be determined based on the assembly process of the fiber laser pump module 400. For example, the one or more second laser clusters 412b may be rotated relative to the one or more first laser clusters 412a to provide the second polarization.

[0164] It is worth noting that the one or more laser clusters 412a, 412b, the phase correctors, and the amplitude-to-phase converters 430a, 430b do not need to be identical.

[0165] The fiber laser pump module 400 may include a dichroism module 460 (i.e., a wavelength-selective reflector). The dichroism module 460 may be configured to block reverse propagation of radiation, which may have a wavelength different from the wavelength emitted by the plurality of laser units. The dichroism module 460 may protect the one or more laser clusters 412a, 412b from reverse propagation power that may arrive from an external source (e.g., a fiber laser) through the optical fiber 450. The dichroism module may be disposed (positioned) downstream of the polarization-sensitive reflector 470.

[0166] For the sake of brevity, optional features associated with the fiber laser pump module 400 that also appear in the embodiments of Figures 1 to 3 and have been described above will not be repeated.

[0167] Figures 5A to 5B A laser cluster 512 according to an embodiment of the present disclosure is schematically shown. Figure 5A A top view of the laser cluster 512 is shown in a perspective view, and Figure 5B A cross section of the laser cluster 512 is shown.

[0168] The laser cluster 512 may have a plurality of coherent laser units 511a, 511b, 511c. Each coherent laser unit may have a plurality of surface-emitting elements, such as surface-emitting element 510. In some embodiments, the plurality of surface-emitting elements may be VCSEL emitting elements. The plurality of surface-emitting elements may be arranged in a small-pitch array. The lateral extent of the coherent laser unit may be represented as D. The lateral extent D may characterize the emission size of the coherent laser unit. For example, the lateral extent D may be a characteristic diameter of one or more light beams emitted by the coherent laser unit. In various examples, when the lateral extent D is square, a characteristic emission area may be provided.

[0169] In some embodiments, the spacing between any two adjacent surface-emitting elements can range from 0.5 to 5 microns. In some embodiments, the length scale of a surface-emitting element can range from 2 to 9 microns. In some embodiments, the plurality of surface-emitting elements 510 can form a hexagonal, square, or rectangular array.

[0170] The plurality of coherent laser units 511a, 511b, 511c may be constructed from a single semiconductor die and may be optically separated from each other (eg, by etching and / or by a sufficient separation distance) to avoid any optical crosstalk.

[0171] The separation of the plurality of coherent laser units 511a, 511b, 511c from one another may result in a non-emitting area therebetween. An electronic contact may be located in the non-emitting area (eg, an electronic wire).

[0172] In some embodiments, the plurality of coherent laser units 511a, 511b, and 511c may include VCSELs and / or a plurality of VCSEL arrays designed based on a reflectivity modulation layer 599 (represented by a block chain), in a manner similar to columns 3 and 4 of the specification of U.S. Patent No. 5,086,430. The die 512 may include a semiconductor substrate 517a (e.g., gallium arsenide) and may include a plurality of repeating epitaxial layers (e.g., made of gallium arsenide, aluminum gallium arsenide, aluminum arsenide, or other compound semiconductors) grown thereon. The plurality of epitaxial layers may include P-doped layers 514a and 514b and N-doped layers 515a and 515b.

[0173] The P-doped layers 514a, 514b and the N-doped layers 515a, 515b may form a plurality of PN junctions. Active regions 513a, 513b may be formed in the plurality of forward-biased PN junctions.

[0174] The active regions 513a and 513b may include multiple quantum wells (e.g., multilayer undoped gallium indium arsenide) separated by multiple barrier layers (e.g., gallium arsenide phosphide). The multiple quantum wells may generate photons through recombination of charge carriers.

[0175] The plurality of active regions 513a, 513b may be stacked using one or more tunnel diode junction regions 516 to provide charge carrier type conversion (eg, from electrons to holes) between the active regions 513a, 513b.

[0176] The P-doped layers 514a, 514b and the N-doped layers 515a, 515b may include multiple reflective mirror regions. The reflective mirror regions may be fabricated, for example, from alternating aluminum arsenide / gallium arsenide layers. The reflective mirror regions may be configured to partially reflect light. Thus, the reflective mirror regions may form laser resonators. The P-doped layers 514a, 514b and the N-doped layers 515a, 515b may include multiple spacer regions. The spacer regions may provide a distance between the reflective mirror regions, thereby determining the resonant wavelength of the coherent laser elements 511a, 511b, 511c.

[0177] The reflectivity-modulating layer 599 can be fabricated from a layer of material that periodically alternates between multiple materials with different reflectivity properties. For example, titanium and gold, or titanium and a gold-coated dielectric layer. The reflectivity-modulating layer 599 can partially serve as a contact layer to the P-doped layer 514b, for example, by providing electrical injection through the multiple titanium-coated portions of the reflectivity-modulating layer 599. The reflectivity-modulating layer 599 can provide a specific mutual optical coupling pattern, such as an array supermode, between the multiple surface-emitting elements in each of the coherent laser units 511a, 511b, and 511c. As a result, the multiple surface-emitting elements of each coherent laser unit can be adjacently coupled and substantially coherent. Furthermore, the multiple surface-emitting elements of a given laser unit do not interfere with the multiple surface-emitting elements of another adjacent laser unit (i.e., the multiple laser units 511a, 511b, and 511c are mutually incoherent).

[0178] The semiconductor die may be mounted on its epitaxial side down to metallized contact pads 502a, 502b above the base plate 501. The contact pad 502a may be electrically connected to the semiconductor substrate 517a via an electrode 518a.

[0179] The plurality of coherent laser units 511a, 511b, 511c may be electrically connected in parallel. For example, the cathodes of the plurality of coherent laser units may be electrically connected via the contact pads 502b, and the anodes of the plurality of coherent laser units may be electrically connected via the semiconductor substrate 517a.

[0180] The base plate 501 can serve as a bare die carrier. The base plate 501 can be made of an electrically insulating material with high thermal conductivity. As described above, the phase corrector 520 can be integrated with the multiple coherent laser units 511a, 511b, and 511c and / or with the entire laser cluster 512. The phase corrector 520 can be integrated with the semiconductor substrate 517a, for example, by etching or depositing it thereon.

[0181] The laser cluster 512 established on a single semiconductor die can provide several watts of optical power. To further scale power, more dies can be excited simultaneously, preferably as a series circuit. To this end, contact pad 502b can be further connected to the cathode electrode 518b of another laser cluster established on another die with a semiconductor substrate 517b. As more laser clusters / dies are added, they can be excited with the same current, and additional drive voltage can be added for each die.

[0182] In some embodiments, semiconductor substrates 517a and 517b may be formed of insulating or semi-insulating materials, and some or all of the plurality of laser units 511a, 511b, and 511c may be connected in series. In some embodiments, the semiconductor die may include only a single coherent laser unit (one of 511a, 511b, and 511c), and the laser cluster 512 may include multiple semiconductor dies.

[0183] It should be noted that the types and parameters of the multiple coherent laser units and surface emitting elements used in this embodiment are not limited. Different embodiments may use different types of SELs, as in the prior art.

[0184] Figure 6A A laser system 666 according to an embodiment of the present disclosure is schematically shown, comprising a plurality of laser clusters established on a corresponding plurality of dies 612 . Figure 6B Showing a Figure 6A The electrical connection arrangement of the laser system.

[0185] Each laser cluster built on a die 612 may include multiple coherent laser units 611 (e.g., nine). The multiple coherent laser units 611 may be incoherent with each other. Multiple coherent laser units in different dies may also be incoherent with each other, for example, optically decoupled.

[0186] The plurality of laser clusters may be electrically connected in series. The cathode electrode 618 may be routed along the perimeter of each die, except for the opening portion (where the substrate 617 may be used to establish electrical connections). In the process, if the plurality of dies are flip-chip bonded to a base plate 601 (e.g., Figure 6B ), the open portion may allow adjacent die to connect without shorting in an area where the contact pad may extend to an adjacent electrode (e.g., as shown in FIG. Figure 5B The plurality of dies may be excited by the series circuit by applying electric drive power to the plurality of terminals marked as “GND” and “+”.

[0187] The plurality of laser clusters of the system are configured such that the current supplied to each laser cluster is in the range of 10 A to 30 A. For example, the number of coherent laser units per laser cluster on a die may be selected to meet the current supply requirement.

[0188] A combination of parallel electrical connections (of the multiple coherent laser units) and series electrical connections (of multiple dies / clusters) can provide flexibility in engineering the laser system 666 according to the present disclosure. Examples include meeting specific heat density, heat distribution, voltage, current, current density, and / or other electrical pumping requirements.

[0189] Figure 7 A fiber coupling assembly 777 according to an embodiment of the present disclosure is schematically shown. The present disclosure allows light from the focusing optical assembly (e.g., Figure 1A to 140 in B) are efficiently coupled into the optical fiber while providing safe handling of stray light due to phase correction or focusing errors.

[0190] The fiber coupling assembly 777 may have a proximal portion 755 and a distal portion 756. In the proximal portion 755, the optical fiber 750 may be surrounded by a first encapsulating medium 751 (e.g., an adhesive) and supported by a block 753. In the distal portion 756, the optical fiber 750 may be surrounded by a second encapsulating medium 752 (e.g., a sealant) and may enter a ferrule 754. The first encapsulating medium 751 may have a refractive index that is close to but higher than the refractive index of the optical fiber. The second encapsulating medium 752 may have a refractive index that is between the refractive index of the optical fiber 750 and the refractive index of the first encapsulating medium 751. In some embodiments, the refractive indices of the first encapsulating medium 751 and the second encapsulating medium 752 may range from 1.45 to 1.6.

[0191] The end of the optical fiber can extend into free space. This allows any incident stray light that propagates entirely outside the fiber to dissipate. Thus, the parasitic power carried by the stray light can escape over a large area. The optical fiber 750 can be surrounded by the first encapsulating medium 751.

[0192] As described above, the first packaging medium 751 may have a refractive index that is close to but higher than the refractive index of the optical fiber 750. This may allow the first packaging medium 751 to extract parasitic light from the optical fiber cladding.

[0193] The first packaging medium 751 and the second packaging medium 752 can firmly lock the position of the optical fiber 750 and ensure its stability. The packaging media 751 and 752 can have low outgassing properties to ensure that the precision optical components within the laser pump module are not contaminated throughout the operating life of the laser pump module.

[0194] The fiber block 753 can be constructed from a material selected to have a high thermal conductivity to allow waste heat generated by absorbing the extracted parasitic optical power to escape through the bottom of the block. The fiber block 753 can thus function as a heat sink. The fiber block 753 can have a refractive index that is higher than the refractive index of the first encapsulating medium 751 to allow the parasitic optical power to be extracted into the fiber block 753. Thus, the fiber block 753 can function as a light sink. Thus, the fiber block 753 can achieve the dual functions of dissipating both light and heat by converting the extracted light into heat and safely dissipating the heat.

[0195] The first portion 755 can remove parasitic light and dissipate several watts of wasted optical power without causing a significant absorption-induced temperature increase. However, residual parasitic power may still remain. This residual parasitic power may pass through high-angle optical elements in the optical fiber 750 or through free-space light that extracts power from the first encapsulating medium 751. This residual parasitic power can be removed by the second portion 756.

[0196] The second portion 756 may include a collar 754 that can accommodate the optical fiber 750 and can be made of a material with high mechanical strength to support and fix the optical fiber 750. The front portion of the collar 754 can serve as a tight aperture to block the free-space light extracted by the first portion 755.

[0197] The inner tube of the ferrule 754 can be filled with the second encapsulating medium 752 (e.g., sealant), which can have a refractive index between the refractive index of the optical fiber and the refractive index of the first encapsulating medium 751. By having a refractive index closer to the refractive index of the optical fiber than the encapsulating medium 751, the encapsulating medium 752 can extract residual low-angle parasitic light from the optical fiber cladding.

[0198] The second portion 756 being longer than the first portion 755 can facilitate extraction of residual low-angle parasitic light, allowing for an extended "modal stripping" length. Thus, the combined cascade of the first and second portions 755, 756, can provide a total modal stripping length sufficient to remove most, or even all, parasitic light from the fiber cladding. This can be used to safely deliver the high-power optical output of the fiber pump module through an extended outer portion of uncooled fiber.

[0199] The second encapsulating medium 752 can provide an impermeable environmental barrier to prevent moisture from entering the fiber optic pump module through the collar 754 .

[0200] The fiber laser pump module described herein can be integrated into applications requiring a high-power laser source. For example, a fiber laser system can include the fiber laser pump module described above.

[0201] Having described and illustrated the principles of the disclosed technology with reference to the illustrated embodiments, it will be appreciated that the illustrated embodiments may be modified in arrangement and detail without departing from such principles. The technology from any example may be combined with the technology described in one or more other examples.

[0202] Thus, in the language of the clauses, the present disclosure provides methods, systems, and circuits according to, but not limited to, the following clauses:

[0203] Item 1. A fiber laser pump module comprising:

[0204] (a) one or more laser clusters, comprising a plurality of laser units arranged in a common plane;

[0205] (i) wherein the plurality of laser units are optically decoupled so that the plurality of light waves emitted by one laser unit do not interfere with the plurality of light waves emitted by another laser unit;

[0206] (ii) wherein the plurality of laser units include at least some coherent laser units, each coherent laser unit including a plurality of semiconductor surface-emitting laser elements optically coupled to one another such that a plurality of light waves emitted by a surface-emitting element interfere with a plurality of light waves emitted by another surface-emitting element;

[0207] (b) one or more phase correctors configured to receive light emitted from the one or more laser clusters; wherein the one or more phase correctors include at least some optical phase correction elements configured to manipulate light emitted by the at least some coherent laser units to generate interference to output a plurality of corrected light beams, the corrected light beams propagating substantially in a single direction and having a far-field pattern, the far-field pattern being predominantly formed by a single main lobe;

[0208] (c) a focusing optical assembly disposed downstream of the one or more phase correctors for focusing the plurality of corrected beams into a focused beam; and

[0209] (d) an optical fiber for receiving and outputting the focused light beam, wherein the input end of the optical fiber is arranged in the focal plane of the focusing optical component.

[0210] Item 2. As described in Item 1, wherein the multiple laser units are arranged according to a first proximity, the first proximity being at least a predefined threshold to avoid mutual optical proximity coupling; and wherein the multiple surface-emitting elements in each coherent laser unit are arranged according to a second proximity, the second proximity being shorter than the predefined threshold to induce mutual optical proximity coupling.

[0211] Clause 3. As described in clause 2, wherein the predefined threshold is less than 10 times a wavelength emitted by the plurality of surface-emitting elements, wherein the wavelength is defined according to light propagation in free space.

[0212] Clause 4. Any of clauses 2 to 3, wherein the predefined threshold is 10 microns.

[0213] Clause 5. As described in any preceding clause, wherein the single main lobe carries at least 50% of the optical power carried by the far-field pattern, preferably at least 75%, more preferably at least 90%, even more preferably at least 99%.

[0214] Clause 6. As described in any preceding clause, wherein the divergence of the plurality of correction beams is at most 3 times the diffraction limit of the laser unit.

[0215] Clause 7. As described in any preceding clause, wherein each laser unit is configured to emit a power of at least 100 milliwatts and a spectral linewidth of less than 1 nanometer, preferably less than 0.5 nanometers.

[0216] Item 8. Any of the preceding items, comprising a plurality of laser clusters, each laser cluster being formed from a separate semiconductor die and comprising one or more laser units.

[0217] Item 9, as described in Item 8, wherein the plurality of laser clusters are electrically connected in series, wherein the cathode of a laser cluster is electrically connected to the anode of a laser cluster.

[0218] Item 10. As described in any preceding item, wherein all laser units in at least one laser cluster are electrically connected in parallel.

[0219] Item 11. As described in any of the preceding items, wherein the plurality of surface-emitting elements include any of the following: a photonic crystal, a photonic lattice, an optical grating, a distributed Bragg reflector (DBR), a distributed feedback (DFB) region, an etched region, a metal region, a dielectric region, a regrown semiconductor region, and a reflectivity modulation region.

[0220] Clause 12. As described in any preceding clause, wherein the plurality of surface emitting elements included in at least one of the at least some coherent laser units are arranged in an array with a periodicity of less than 10 microns.

[0221] Clause 13. As described in any preceding clause, wherein the one or more phase correctors are configured to provide amplitude-to-phase conversion for increasing optical power propagating along the single direction.

[0222] Item 14. As described in any of the preceding items, wherein the one or more phase correctors include any of a phase plate, a phase mask, a phase shift mask, a phase delay plate, a wavefront corrector, a metasurface, a Fourier hologram, a transmission grating, a phase grating, a Dammann grating, and a diffractive optical element.

[0223] Clause 15. As described in any preceding clause, wherein the one or more phase correctors include any of phase stages, pillars, blocks, slits, nanopillars, nanoblocks, and nanoslits.

[0224] Item 16. Any preceding item, having an output brightness of at least 2 MW / (sq.cm×srad).

[0225] Item 17. As described in any preceding item, wherein the emission wavelength of the plurality of surface-emitting elements ranges from 770 nm to 1070 nm, preferably one of 915 nm and 976 nm.

[0226] Clause 18. As set out in any of the preceding clauses, including:

[0227] (a) one or more first laser clusters configured to emit a plurality of light waves in a first polarization;

[0228] (b) one or more second laser clusters configured to emit a plurality of light waves in a second polarization; and

[0229] (c) a polarization-sensitive reflector configured to combine the emission lights emitted by the one or more first laser clusters and the one or more second laser clusters.

[0230] Item 19. As described in any of the preceding items, comprising a dichroic module configured to block reverse propagation of multiple wavelengths, the wavelengths being different from the wavelengths emitted by the one or more laser clusters, wherein the dichroic module is positioned between the one or more phase correctors and the focusing optical component.

[0231] Clause 20. The method of clause 19, wherein the dichroic module is tilted relative to the single direction of the plurality of correction beams.

[0232] Clause 21. Any of the preceding clauses, comprising a microlens array disposed between the plurality of laser units and the one or more phase correctors, the microlens array being configured for Fourier imaging of a plurality of light waves emitted by at least some of the plurality of laser units, wherein at least some of the microlenses correspond to at least some of the plurality of laser units.

[0233] Clause 22. Any preceding clause, wherein the phase corrector is integrated into the laser cluster.

[0234] Clause 23. As described in any preceding clause, wherein the focusing optical assembly includes two cylindrical lenses along different axes.

[0235] Clause 24. As described in any preceding clause, wherein the focusing optical component includes a single lens.

[0236] Clause 25. Any preceding clause, wherein light emitted by the plurality of coherent laser units forms a plurality of far-field lobes, preferably four lobes.

[0237] Clause 26. As described in any preceding clause, wherein the plurality of laser units comprise any of the semiconductor materials of gallium arsenide, aluminum arsenide, aluminum gallium arsenide, gallium indium arsenide, gallium indium arsenide phosphide, indium phosphide, and gallium nitride.

[0238] Clause 27. Any preceding clause, wherein the plurality of laser units comprises a plurality of tunnel contacts or a plurality of buried tunnel contacts.

[0239] Item 28. Any preceding item, wherein the emitted light is emitted from a substrate side of the plurality of laser units.

[0240] Clause 29. The fiber laser pump module according to any preceding clause, configured to receive power from a power supply unit configured to supply power to a plurality of edge-emitting laser modules.

[0241] Clause 30. Any preceding clause, wherein the current supplied by the power supply unit is in the range of 10A to 30A.

[0242] Clause 31. As described in any preceding clause, wherein a first portion of the optical fiber is surrounded by a first packaging medium and a second portion of the optical fiber is surrounded by a second packaging medium in a ring, wherein the first and second packaging media have a refractive index that is close to but higher than the refractive index of the optical fiber.

[0243] Item 32. As described in Item 31, wherein the refractive index is in the range of 1.45 to 1.6.

[0244] Clause 33. A fiber laser system comprising a fiber laser pump module as described in any preceding clause.

[0245] Item 34. A solid-state optical gain medium comprising either erbium and ytterbium and excited by the optical power of a fiber laser pump module as described in any preceding item.

Claims

1. A fiber laser pump module, characterized in that include: (a) one or more laser clusters comprising a plurality of laser units arranged in a common plane; i) wherein the plurality of laser units are optically decoupled such that the plurality of light waves emitted by one laser unit do not interfere with the plurality of light waves of another laser unit; ii) wherein the plurality of laser units include at least some coherent laser units, each coherent laser unit including a plurality of semiconductor surface-emitting laser elements optically coupled to one another such that a plurality of light waves emitted by a surface-emitting element interfere with a plurality of light waves emitted by another surface-emitting element; (b) one or more phase correctors configured to receive light emitted from the one or more laser clusters; wherein the one or more phase correctors include at least some optical phase correction elements configured to manipulate light emitted by the at least some coherent laser units to generate interference to output a plurality of corrected light beams, the corrected light beams propagating substantially in a single direction and having a far-field pattern, the far-field pattern being predominantly formed by a single main lobe; (c) a focusing optical assembly disposed downstream of the one or more phase correctors for focusing the plurality of corrected beams into a focused beam; as well as (d) an optical fiber for receiving and outputting the focused light beam, wherein the input end of the optical fiber is arranged in the focal plane of the focusing optical component.

2. The fiber laser pump module of claim 1 , wherein the plurality of laser units are arranged in a first proximity that is at least a predefined threshold to avoid mutual optical proximity coupling; and wherein the plurality of surface-emitting elements in each coherent laser unit are arranged in a second proximity that is shorter than the predefined threshold to induce mutual optical proximity coupling.

3. The fiber laser pump module of claim 2, wherein the predefined threshold is less than 10 times a wavelength emitted by the plurality of surface-emitting elements, wherein the wavelength is defined according to light propagation in free space. The fiber laser pump module according to claim 2 , wherein the predefined threshold is 10 μm.

5. The fiber laser pump module of claim 1 , wherein the single main lobe carries at least 50% of the optical power carried by the far-field pattern, preferably at least 75%, more preferably at least 90%, even more preferably at least 99%.

6. The fiber laser pump module of claim 1, wherein the divergence of the plurality of correction beams is at most 3 times the diffraction limit of the laser unit.

7. The fiber laser pump module of claim 1, wherein each laser unit is configured to emit a power of at least 100 mW and a spectral linewidth of less than 1 nm, preferably less than 0.5 nm.

8. The fiber laser pump module according to claim 1, comprising a plurality of laser clusters, each laser cluster being formed by a separate semiconductor die and comprising one or more laser units.

9. The fiber laser pump module according to claim 8, wherein the plurality of laser clusters are electrically connected in series, wherein the cathode of one laser cluster is electrically connected to the anode of the next laser cluster.

10. The fiber laser pump module according to claim 1, wherein all laser units in at least one laser cluster are electrically connected in parallel.

11. The fiber laser pump module of claim 1 , wherein the plurality of surface-emitting elements comprises any one of the following: a photonic crystal, a photonic lattice, an optical grating, a distributed Bragg reflector, a distributed feedback region, an etched region, a metal region, a dielectric region, a regrown semiconductor region, and a reflectivity-modulated region.

12. The fiber laser pump module of claim 1, wherein at least one of said at least some coherent laser units comprises said plurality of surface emitting elements arranged in an array with a period of less than 10 microns.

13. The fiber laser pump module of claim 1, wherein the one or more phase correctors are configured to provide amplitude-to-phase conversion for increasing optical power propagating along the single direction.

14. The fiber laser pump module of claim 1 , wherein the one or more phase correctors comprise any one of a phase plate, a phase mask, a phase shift mask, a phase retardation plate, a wavefront corrector, a metasurface, a Fourier hologram, a transmission grating, a phase grating, a Dammann grating, and a diffractive optical element.

15. The fiber laser pump module of claim 1, wherein the one or more phase correctors comprise any of a phase stage, a rod, a block, a slit, a nanorod, a nanoblock, and a nanoslit.

16. The fiber laser pump module of claim 1, having an output brightness of at least 2 MW / (sq.cm×srad).

17. The fiber laser pump module according to claim 1, wherein the emission wavelengths of the plurality of surface-emitting elements range from 770 nm to 1070 nm, preferably one of 915 nm and 976 nm.

18. The fiber laser pump module according to claim 1, comprising: (a) one or more first laser clusters configured to emit a plurality of light waves in a first polarization; (b) one or more second laser clusters configured to emit a plurality of light waves in a second polarization; as well as (c) a polarization-sensitive reflector configured to combine the emission lights emitted by the one or more first laser clusters and the one or more second laser clusters.

19. The fiber laser pump module of claim 1 , comprising a dichroic module configured to block counter-propagation of a plurality of wavelengths different from wavelengths emitted by the one or more laser clusters, wherein the dichroic module is positioned between the one or more phase correctors and the focusing optics.

20. The fiber laser pump module of claim 19, wherein the dichroic module is tilted relative to the single direction of the plurality of correction beams.

21. The fiber laser pump module of claim 1 , comprising a microlens array disposed between the plurality of laser units and the one or more phase correctors, the microlens array being configured for Fourier imaging of a plurality of light waves emitted by at least some of the plurality of laser units, wherein at least some of the microlenses correspond to at least some of the plurality of laser units.

22. The fiber laser pump module of claim 1, wherein the phase corrector is integrated into the laser cluster.

23. The fiber laser pump module of claim 1, wherein the focusing optics comprises two cylindrical lenses along different axes.

24. The fiber laser pump module of claim 1, wherein the focusing optics assembly comprises an Einzel lens.

25. The fiber laser pump module of claim 1, wherein light emitted by the plurality of coherent laser units forms a plurality of far-field lobes, preferably four lobes.

26. The fiber laser pump module of claim 1, wherein the plurality of laser units comprise any one of semiconductor materials of gallium arsenide, aluminum arsenide, aluminum gallium arsenide, gallium indium arsenide, gallium indium arsenide phosphide, indium phosphide, and gallium nitride.

27. The fiber laser pump module of claim 1, wherein the plurality of laser units comprise a plurality of tunnel junctions or a plurality of buried tunnel junctions.

28. The fiber laser pump module of claim 1, wherein the emission light is emitted from a substrate side of the plurality of laser units.

29. The fiber laser pump module of claim 1, configured to receive power from a power supply unit configured to supply power to a plurality of edge emitting laser modules. 30 . The fiber laser pump module according to claim 1 , wherein the current supplied by the power supply unit is in a range of 10 A to 30 A.

31. The fiber laser pump module of Claim 1, wherein a first portion of the optical fiber is surrounded by a first encapsulating medium and a second portion of the optical fiber is surrounded by a second encapsulating medium in a ferrule, wherein the first and second encapsulating media have a refractive index that is close to but higher than a refractive index of the optical fiber.

32. The fiber laser pump module of claim 31 , wherein the refractive index is in the range of 1.45 to 1.

6.

33. A fiber laser system, characterized in that Comprising a fiber laser pump module according to any preceding claim.

34. A solid-state optical gain medium, characterized in that The optical fiber laser comprises any one of erbium and ytterbium, and is excited by the optical power of the fiber laser pump module according to any one of claims 1 to 32.

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