Master oscillator power amplifier laser system and method - Patents.com

Abstract

A merged master oscillator power amplifier (MOPA) laser module and method of manufacture thereof, the MOPA including a prefabricated chassis including a plurality of surfaces, a master oscillator laser (MO) permanently affixed to at least a first surface of the plurality of surfaces, a power amplifier (PA) permanently affixed to at least a second surface of the plurality of surfaces, and a beam delivery system (BTS) permanently affixed to the prefabricated chassis, wherein a spatial relationship between the at least one first surface and the at least one second surface determines alignment between the MO and the PA, and the BTS includes a plurality of optical elements for delivering light output from the MO to the PA for amplification.

Description

Detailed Description of the Invention

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application is related to and claims priority to U.S. Provisional Patent Application No. 63 / 303,136, filed January 26, 2022, which is incorporated herein by reference in its entirety.

[0002] [Field] This disclosure relates to photonic systems, methods, and articles of manufacture, and more particularly to systems and methods for Master Oscillator Power Amplifier (MOPA) lasers used in infrared (IR) photonics.

[0003] 〔background〕 Lasers operating in the short-wave infrared (SWIR) portion of the electromagnetic spectrum can be difficult to mass-produce, especially when low production costs are required. Therefore, there is a need in the art for MOPA laser systems, including passively Q-switched (P-QS) SWIR lasers that can be mass-produced at low cost. Current solutions for producing and assembling MOPA laser systems can require a large number of components, the use of multiple alignment tools, test tools, and highly complex system assembly processes. For example, master oscillator fiber amplifiers (MOFAs) require precise and highly efficient coupling, for example, from solid-state lasers to single- or multimode fibers. For high-power sources, coupling is extremely challenging because the spatial geometry of the laser can be complex, which can require complex beam-shaping optics, precise micropositioning, and active and passive stabilizers.

[0004] There is a need for fast and simple alignment between and within various modules, which could have advantages over current solutions for reducing costs, assembly time, qualification phases, and validation phases.

[0005] 〔overview〕 In various exemplary embodiments, a merged master oscillator power amplifier (MOPA) laser module is provided, the merged MOPA laser module including: a prefabricated chassis including a plurality of surfaces; a master oscillator laser (MO) enduringly affixed to a first surface of at least one of the plurality of surfaces; a power amplifier (PA) permanently affixed to a second surface of at least one of the plurality of surfaces; and a beam delivery system (BTS) permanently affixed to the prefabricated chassis, wherein a spatial relationship between at least one of the first surface and at least one of the second surfaces determines alignment between the MO and the PA, and the BTS includes a plurality of optical elements for delivering light output from the MO to the PA for amplification.

[0006] In some embodiments, the MO is a passively Q-switched laser.

[0007] In some embodiments, the MO includes a crystalline saturable absorber rigidly coupled to a crystalline gain medium of the MO, and in some such embodiments, the MO further includes a high-reflectivity mirror and an output coupler rigidly coupled to the gain medium and the saturable absorber, such that the MO is a monolithic microchip P-QS laser.

[0008] In some embodiments, at least one of the first surface and at least one of the second surface are polished surfaces that are parallel to one another.

[0009] In some embodiments, the amplifier includes at least one pump and a flat crystal having an average thickness of less than 20 millimeters that is pumped by the pump, the MO light passes through the flat crystal in multiple passes and is amplified in each of the passes, and the chassis includes at least one polished surface that acts as a mirror to reflect the light from the flat crystal back into the flat crystal at least once.

[0010] In some embodiments, the merged MOPA further includes at least one lens and folding optics, wherein the optical axis of the light output by the MOPA continues to a position on an incident position on the side of the PA so that light incident on the PA along the optical axis is amplified and emitted at the output optical axis of the amplifier, and the position of the BTS relative to the chassis is such that light enters the BTS along the optical axis, is deflected by the folding optics and manipulated by at least one of the lenses, and then exits the BTS along the optical axis.

[0011] In some embodiments, the frequency of a pump source of the MO is between 750 nanometers (nm) and 850 nm, and the frequency of light emitted by the MO is between 1,300 nm and 1,400 nm; the frequency of a pump source of the PA is between 750 nm and 850 nm, and the frequency of light emitted by the PA is between 1,300 nm and 1,400 nm; the gain medium of the MO comprises a crystalline material that is neodymium-doped yttrium aluminum garnet (Nd:YAG); and the saturable absorber of the MO is (a) Trivalent vanadium-doped yttrium aluminum garnet (V 3+ :YAG) and (b) Divalent cobalt-doped crystalline material and the PA comprises a Nd:YAG flat crystal.

[0012] In some embodiments, at least a portion of the chassis is part of a thermoelectric cooler (TEC) operable to cool at least one of the MO and the PA.

[0013] In some embodiments, the combined MOPA further includes an intermediate mechanical coupling permanently affixed between the MO or a component of the PA and a corresponding surface of the chassis, and the degree of dislocation caused by the intermediate mechanical coupling and the corresponding surface is determined based on optical measurements of light emitted by the MO.

[0014] In some embodiments, the merged MOPA further includes an internal optical sensor for measuring a sensed intensity indicative of an intensity of an internal light beam emitted by at least one of the MO and the PA, and a controller operable to trigger movement of at least one optical component of the MOPA laser module to increase the intensity of the internal light beam.

[0015] In some embodiments, the merged MOPA further includes an internal temperature sensor for measuring a temperature sensed within the MOPA laser module, and a controller operable to trigger movement of at least one optical component of the MOPA laser module based on the measured temperature.

[0016] In some embodiments, the merged MOPA further includes an internal optical sensor for measuring a sensed intensity indicative of an intensity of an internal light beam emitted by at least one of the MO and the PA, and a controller operable to trigger a change in the electric magnitude of a controlled component of the MOPA laser module to increase the intensity of the internal light beam.

[0017] In some embodiments, the merged MOPA further includes an internal temperature sensor for measuring a temperature sensed within the MOPA laser module, and a controller operable to trigger changes in electrical magnitudes of controlled components of the MOPA laser module based on the measured temperature and temperature compensation information in a tangible memory module accessible by the controller.

[0018] In some embodiments, the BTS includes an optical entrance for receiving an optical beam from an MO laser module along an input optical axis, an optical exit for emitting the steered optical beam toward a PA along an output optical axis, a plurality of lenses, at least one of which is shaped to steer the optical beam and is shaped to fit into at least one customized three-dimensional (3D) structure of a chassis, and a plurality of flex optical components, including at least one component selected from the group consisting of mirrors and prisms, operable to deflect light entering the BTS along the input optical axis toward at least one of the plurality of lenses and to deflect light coming from at least one other of the plurality of lenses toward the output optical axis, at least one of which is shaped to steer the optical beam and is shaped to fit into at least one customized 3D structure of the chassis. In some embodiments, the chassis has at least a portion including at least one customized 3D structure and at least one customized 3D structure. In some embodiments, at least one of the plurality of bent optical components is controllably movable by at least one other component of the BTS to adjust the position of the respective bent optical component relative to the respective customized 3D structure. In some embodiments, at least one of the plurality of bent optical components is a pentaprism having four active surfaces, the pentaprism operable to internally reflect the light beam twice within the pentaprism before emitting the light beam out of the pentaprism. In some embodiments, at least one of the plurality of bent optical components is a retroreflector having at least three active surfaces, the retroreflector operable to internally reflect the light beam twice within the retroreflector before emitting the light beam out of the retroreflector.In some embodiments, the exit optical axis is a continuation of the entrance optical axis.

[0019] In various exemplary embodiments, a method for manufacturing a MOPA laser module is provided, comprising: permanently bonding at least one component of an MO and at least one component of a PA to different surfaces of a prefabricated chassis; and permanently coupling a BTS to the prefabricated chassis after the bonding of the at least one component of the MO and the at least one component of the PA, wherein the bonding of the at least one component of the MO and the at least one component of the PA to the prefabricated chassis determines alignment between the MO and the PA, and the BTS includes a plurality of optical elements for transmitting light output from the MO to the PA for amplification.

[0020] In some embodiments, the bonding step includes the steps of directing the MO directly toward the PA, sensing an output of the PA resulting from irradiation, adjusting an alignment between the MO and the PA based on the results of the sensing step, and bonding at least one component of at least one of the MO and the PA based on the adjusted alignment.

[0021] In some embodiments, the method further includes measuring the output of the PA at two or more different temperatures and two or more different states of at least one controllable optical component (COC) of the BTS, calculating temperature compensation information for at least one of the COCs, and storing the temperature compensation information in a tangible memory module readable by a controller operable to change the state of at least one of the COCs.

[0022] In some embodiments, the method further includes measuring the output power of at least one thermoelectric cooler (TEC) of the MOPA laser module at two or more different temperatures and two or more different states of the PA, calculating temperature compensation information for the at least one TEC, and storing the temperature compensation information in a tangible memory module readable by a controller operable to change the state of the at least one TEC.

[0023] In some embodiments, the method further includes measuring the output of at least one pump of the MO or the PA at two or more different temperatures and two or more different states, calculating temperature compensation information for at least one of the pumps, and storing the temperature compensation information in a tangible memory module readable by a controller operable to change the state of at least one of the pumps.

[0024] In some embodiments, the permanently bonding step is preceded by a step of polishing at least one first surface and at least one second surface of the chassis so that they are parallel to one another, and the permanently bonding step includes a step of permanently bonding at least one of the components of the MO to the first surface and a step of permanently bonding at least one of the components of the PA to the second surface.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS In order that the present disclosure may be understood and how it may be carried out in practice, several embodiments will now be described, by way of non-limiting example only, by way of example of the subject matter of the present disclosure, with reference to the accompanying drawings, in which: FIG. 1 is a schematic functional block diagram illustrating an example of a short-wave infrared (SWIR) optical system; 2A, 2B, and 2C are schematic functional block diagrams illustrating examples of P-QS lasers; FIG. 3 is a schematic functional diagram illustrating one exemplary implementation of a SWIR optical system; FIG. 4 is a schematic functional diagram illustrating another exemplary implementation of a SWIR optical system; FIG. 5 is a schematic functional block diagram illustrating an example of a SWIR optical system; FIG. 6A is a flow chart illustrating an example of a method for manufacturing components for a P-QS laser; 6B and 6C include some conceptual timelines for carrying out the methods described above; 7 and 8 show exemplary exploded perspective projections of a gain medium amplifier (GMA) according to an embodiment of the disclosed subject matter; 9 and 10 show exemplary exploded perspective projections of a gain medium amplifier (GMA) and an amplified laser radiation source according to an embodiment of the presently disclosed subject matter; 11A, 11B, and 11C are schematic functional block diagrams illustrating an exemplary MOPA system in accordance with the subject matter of the present disclosure; FIG. 12 is a side view illustrating exemplary components and a chassis of a MOPA laser module in accordance with the subject matter of the present disclosure; 13A, 13B, 13C, 13D, and 13E show exemplary beam delivery systems in accordance with the subject matter of the present disclosure; FIG. 14 is a flowchart of an exemplary process for a method of manufacturing a merged MOPA laser module according to some embodiments of the presently disclosed subject matter.

[0026] Detailed Description In order that the present disclosure may be understood and how it may be carried out in practice, several embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings. It will be understood that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Furthermore, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or similar elements.

[0027] In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the present disclosure. However, it will be understood by those skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present disclosure.

[0028] In the drawings and descriptions set forth, identical reference numbers indicate components that are common to different embodiments or configurations.

[0029] The terms "computer," "processor," and "controller" should be interpreted broadly to encompass any type of electronic device having data processing capabilities, including, by way of non-limiting example, a personal computer, a server, a computing system, a communication device, a processor (e.g., a digital signal processor (DSP), a microcontroller, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), etc.), any other electronic computing device, and / or any combination thereof.

[0030] The operations of the teachings herein may be performed by a computer specially created for the desired purpose, or may be performed by a general-purpose computer specially configured for the desired purpose by a computer program stored on a computer-readable storage medium, particularly a non-transitory computer-readable storage medium.

[0031] As used herein, the phrases "for example," "such," "for instance," and variations thereof describe non-limiting embodiments of the subject matter disclosed herein. As used herein, reference to "one case," "some cases," "other case," or variations thereof means that a particular configuration, structure, or characteristic described in connection with one or more embodiments is included in at least one embodiment of the subject matter disclosed herein. Thus, appearances of the phrases "one case," "some cases," "other case," or variations thereof do not necessarily refer to the same embodiment(s).

[0032] It will be understood that certain features of the subject matter disclosed herein, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the subject matter disclosed herein, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

[0033] In embodiments of the presently disclosed subject matter, one or more of the stages shown may be performed in a different order and / or one or more groups of the stages may be performed simultaneously, or vice versa. Each figure shows a general schematic of a system architecture according to embodiments of the presently disclosed subject matter. Each module in the figure may be configured by any combination of software, hardware, and / or firmware that performs the functions as defined and described herein. Each module in the figure may be centrally located in one location or may be distributed across two or more locations.

[0034] Any reference herein to a method shall apply mutatis mutandis (i) to a system capable of carrying out that method, and (ii) to a non-transitory computer-readable medium storing instructions that, once executed by a computer, produce the result of carrying out that method.

[0035] Any reference herein to a system shall also apply mutatis mutandis to (i) a method that may be performed by the system, and (ii) a non-transitory computer-readable medium storing instructions that may be executed by the system.

[0036] 1 is a schematic functional block diagram illustrating one embodiment of a SWIR optical system 100 in accordance with an embodiment of the disclosed subject matter. System 100 includes at least a passively Q-switched (P-QS) laser 200. However, as shown in FIG. 5, system 100 may further include additional components, such as: a. Sensor 102 operative to sense reflected light from the FOV of system 100, particularly reflected illumination of laser 200 reflected from external object 500. With reference to other examples, sensor 102 may be implemented as an imaging receiver, PDA, or light detection device as discussed in this disclosure. b. A processor 104 that operates to process the sensing results of the sensor 102. The output of the processing may be an image of the FOV, a depth model of the FOV, a spectral analysis of one or more portions of the FOV, information about identified objects within the FOV, light statistics about the FOV, or any other type of output. In reference to other examples, the processor 104 may be implemented as any of the processors discussed in this disclosure. c. Controller 106, which operates to control the behavior of laser 200 and / or processor 104. For example, controller 106 may include control of timing, synchronization, and other operating parameters of processor 104 and / or laser 200.

[0037] Optionally, system 100 may include a SWIR PDA 108 that is sensitive to the wavelength of the laser. The SWIR optical system may then function as an active SWIR camera, a SWIR time of flight (ToF) sensor, a SWIR light detection and ranging (LIDAR) sensor, etc. The ToF sensor may be sensitive to the wavelength of the laser. Optionally, the PDA may be a CMOS-based PDA that is sensitive to the SWIR frequencies emitted by laser 200, such as a CMOS-based PDA designed and manufactured by TriEye, Inc. (Tel Aviv, Israel).

[0038] The processor 104 may be used to process detection data from the SWIR PDA (or any other light-sensitive sensor of the system 100). For example, the processor may process the detection information to provide a SWIR image of the field-of-view (FOV) of the system 100, detect objects within the FOV, etc. Optionally, the SWIR optical system may include a time-of-flight (ToF) SWIR sensor sensitive to the wavelength of the laser and a controller operative to synchronize operation of the ToF SWIR sensor and the P-QS SWIR laser to detect the distance to at least one object within the field-of-view of the SWIR optical system. Optionally, the system 100 may include a controller 106 operative to control one or more aspects of operation of the laser 200 or other components of the system, such as a photodetector array (e.g., a focal plane array (FPA)). For example, some parameters of the laser that may be controlled by the controller include timing, duration, intensity, focusing, etc. Although not required, the controller may control operation of the laser based on the PDA's detection results (either directly or based on processing by a processor). Optionally, the controller may operate to control a laser pump or other type of light source to affect activation parameters of the laser. Optionally, the controller may operate to dynamically change the pulse repetition rate. Optionally, the controller may operate to control dynamic modification of the light-shaping optics, for example, to improve the signal-to-noise ratio (SNR) in a particular region of the field of view. Optionally, the controller may operate to control the illumination module to dynamically change pulse energy and / or duration (e.g., in the same manner as is possible for other P-QS lasers, such as by changing the focusing of the pump laser).

[0039] Further optionally, system 100 may include a temperature control (e.g., a passive temperature control, an active temperature control) for controlling the temperature of the laser generally or one or more of its components (e.g., of the pump diode). Such a temperature control may include, for example, a thermoelectric cooler (TEC), a fan, a heat sink, a resistive heater under the pump diode, etc.

[0040] Further optionally, system 100 may include another laser used to bleach at least one of gain medium (GM) 202 and saturable absorber (SA) 204. Optionally, system 100 may include an internal photosensitive detector (e.g., one or more PDs such as PDA 108) operative to measure the time at which laser 200 generates a pulse (e.g., as PD 226 described above). In such a case, controller 106 may operate, based on timing information obtained from the internal photosensitive detector, to issue a trigger signal to PDA 108 (or other type of camera or sensor 102) that detects reflection of the laser light from an object within the field of view of system 100.

[0041] The primary industry requiring large quantities of lasers in the aforementioned spectral range (1.3-1.5 μm) is the electronics industry for optical data storage. This industry has driven down the cost of diode lasers to less than a few dollars per watt per device. However, these lasers are not suitable for other industries, such as the automotive industry, which require lasers with significantly higher peak powers and beam brightness and operate under harsh environmental conditions.

[0042] It should be noted that there is no scientific consensus regarding the range of wavelengths that are considered part of the SWIR spectrum, however, for purposes of this disclosure, the SWIR spectrum includes electromagnetic radiation with wavelengths longer than those in the visible spectrum and encompassing at least the spectral range of 1,300 nm to 1,500 nm.

[0043] While not limited to such applications, one or more P-QS lasers 200 may be used as an illumination source in any imaging system. Laser 200 may also be used in any other electro-optical (EO) system operating in the SWIR range that requires pulsed illumination, such as lidar, spectroscopy, communication systems, etc. It should be noted that the proposed laser 200, and the method for manufacturing such a laser, enable mass manufacturing of lasers operating in the SWIR spectral range at relatively low production costs.

[0044] Referring again to FIG. 1 , P-QS laser 200 includes at least a crystalline GM 202, a crystalline SA 204, and an optical cavity 206 in which the aforementioned crystalline materials are confined so that light propagating within gain medium 202 can be enhanced toward generating a laser light beam 212 (e.g., as shown in FIG. 3 ). The optical cavity, also known by the terms “optical resonator” and “resonating cavity,” includes a high-reflectivity mirror 208 (also referred to as a “high reflector” or “HR”) and an output coupler 210. Described below are several unique and novel combinations of various types of crystalline materials and the use of various manufacturing techniques to fabricate the lasers that enable the mass production of affordable lasers in the SWIR spectral range. General details generally known in the art regarding P-QS lasers are not provided here for the sake of brevity of this disclosure, but are readily available from a variety of resources. A saturable absorber in a laser functions as a Q-switch for the laser, as is known in the art. The term "crystalline material" broadly includes any material in either single-crystal or polycrystalline form.

[0045] The dimensions of the coupled crystalline gain medium and crystalline SA can depend on the design objectives of a particular P-QS laser 200. In one non-limiting example, the combined length of the SA and GM is between 5 and 15 millimeters. In one non-limiting example, the combined length of the SA and GM is between 2 and 40 millimeters. In one non-limiting example, the diameter of the combined SA and GM (e.g., when a round cylinder or when confined within an imaginary such cylinder) is between 2 and 5 millimeters. In one non-limiting example, the diameter of the combined SA and GM is between 0.5 and 10 millimeters.

[0046] The P-QS laser 200 includes a gain medium crystalline material (GMC) rigidly connected to an SA crystalline material (SAC). Rigid coupling may be achieved by any method known in the art, such as using adhesives, diffusion bonding, composite crystal bonding, or growing one on top of the other. However, as described below, rigid coupling of ceramic forms of crystalline material can be achieved using simple and inexpensive means. Note that the GMC and SAC materials may be rigidly connected to each other directly, or, optionally, via an intermediate object (e.g., another crystal). In some implementations, both the gain medium and the SA are connected by doping different portions of a single piece of crystalline material with different dopants (e.g., as described below for SAC and GMC materials) or by co-doping a single piece of crystalline material, doping the same volume of the crystalline material with two dopants (e.g., N 3+ and V 3+ The gain medium may be implemented in a single piece of crystalline material (ceramic YAG co-doped with GMC). Optionally, the gain medium may be grown on a single crystal saturable absorbing substrate (e.g., using liquid phase epitaxy (LPE)). It should be noted that separate GMC and SA crystalline materials are discussed extensively in the following disclosure, and a single piece of ceramic crystalline material doped with two dopants may also be used mutatis mutandis in any of the following implementations.

[0047] 2A, 2B, and 2C are schematic functional block diagrams illustrating an example of a P-QS laser 200 in accordance with the subject matter of the present disclosure. In FIG. 2A, two dopants are implemented in two portions of a common crystalline material 214 (which serves as both the GM and the SA). In contrast, in FIG. 2B, the two dopants are interchangeably implemented in a common block of the common crystalline material 214 (in the illustrated case, the entire common crystal). Optionally, the GM and SA may be implemented in a single piece of crystalline material doped with neodymium and at least one other material. Optionally (e.g., as illustrated in FIG. 2C), either or both of the output coupler 210 and the high-reflectivity mirror 208 may be glued directly to one of the crystalline materials (e.g., a crystal combining the GM or the SA, or both).

[0048] At least one of the SAC and the GMC is a ceramic crystalline material that is a related crystalline material (e.g., doped yttrium aluminum garnet, vanadium-doped YAG) in ceramic form (e.g., polycrystalline form). Having the crystalline materials (e.g., both crystalline materials) in ceramic form allows for higher volume and lower cost production. For example, instead of growing separate single crystalline materials in a slow and limited process, polycrystalline materials may be produced by powder sintering (i.e., compressing and optionally heating powder to form a solid mass), low-temperature sintering, vacuum sintering, etc. Sintering one crystalline material (SAC or GMC) onto the other may eliminate complex and costly processes such as grinding, diffusion bonding, surface activated bonding, etc. Optionally, at least one of the GMC and the SAC is polycrystalline. Optionally, both the GMC and the SAC are polycrystalline.

[0049] Referring to the combinations of crystalline materials from which the GMC and SAC may be made, such combinations may include: a. GMC is ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG), and SAC is (a) ceramic three-valence vanadium-doped yttrium aluminum garnet (V 3+ :YAG), or (b) a ceramic cobalt-doped crystalline material. Optionally, the ceramic cobalt-doped crystalline material may be a ceramic divalent cobalt-doped crystalline material. In these alternatives, both the Nd:YAG and the SAC selected from the aforementioned group are in ceramic form. The cobalt-doped crystalline material is a crystalline material doped with cobalt. Examples include cobalt-doped spinel (Co:Spinel, or Co 2+ :MgAl2O4), cobalt-doped zinc selenide (Co 2+ :ZnSe), cobalt-doped YAG (Co 2+ Although not necessarily so, the high reflectivity mirror and SA in this option may optionally be rigidly connected to the gain medium and SA such that the P-QS laser is a monolithic microchip P-QS laser (e.g., as illustrated in Figures 3 and 5). b. GMC is ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG), and SAC is (a) trivalent vanadium-doped yttrium aluminum garnet (V 3+ The P-QS laser 200 is a non-ceramic SAC selected from the group of doped ceramic materials consisting of (a) YAG (YAG), and (b) cobalt-doped crystalline material. Optionally, the cobalt-doped crystalline material may be a divalent cobalt-doped crystalline material. In such a case, the high-reflectivity mirror 208 and output coupler 210 are rigidly connected to the gain medium and SA such that the P-QS laser 200 is a monolithic microchip P-QS laser. c. Ceramic neodymium-doped rare earth element crystalline material, GMC, and SAC are (a) trivalent vanadium-doped yttrium aluminum garnet (V 3+ Optionally, the cobalt-doped crystalline material may be a divalent cobalt-doped crystalline material. Optionally, but not necessarily, the high-reflectivity mirror 208 and output coupler 210 in this option may be rigidly connected to the gain medium and SA, such that the P-QS laser 200 is a monolithic microchip P-QS laser.

[0050] It should be noted that in any of these implementations, the doped crystalline material may be doped with two or more dopants. For example, SAC may be doped with the primary dopant disclosed above and at least one other doping material (e.g., in a relatively small amount). A neodymium-doped rare earth crystalline material is a crystalline material whose unit cell includes a rare earth element (one of a well-defined group consisting of 15 chemical elements, including the 15 lanthanides, as well as scandium and yttrium) doped with neodymium (e.g., triply ionized neodymium) replacing the rare earth element in a portion of the unit cell. A few non-limiting examples of neodymium-doped rare earth crystalline materials that can be used in the present disclosure are as follows: a. Nd:YAG (mentioned above), neodymium-doped tungstic acid yttrium potassium (Nd:KYW), neodymium-doped yttrium lithium fluoride (Nd:YLF), neodymium-doped yttrium orthovanadate (YVO4). In each of these cases, the rear earth element is neodymium; b. neodymium-doped gadolinium orthovanadate (Nd:GdVO4), neodymium-doped gadolinium gallium garnet (Nd:GGG), neodymium-doped potassium-gadolinium tungstate (Nd:KGW). In each of these cases, the rear earth element is gadolinium, Gd; c. neodymium-doped lanthanum scandium borate (Nd:LSB), where the rare earth element is scandium; d. Other neodymium-doped rare earth crystalline materials may be used, in which case the rare earth may be yttrium, gadolinium, scandium, or any other rare earth element.

[0051] The following discussion applies to any of the optional combinations of GMC and SAC.

[0052] Optionally, the GMC is directly and rigidly connected to the SAC. Alternatively, the GMC and SAC may be indirectly connected (e.g., the SAC and GMC are each connected through one or more intermediate crystalline materials and / or through one or more other solid materials transparent to the relevant wavelengths). Optionally, one or both of the SAC and GMC are transparent to the relevant wavelengths.

[0053] Optionally, the SAC is a cobalt-doped spinel (CoCo 2+ Optionally, the SAC may be cobalt-doped YAG (Co:YAG). Optionally, this may allow the same YAG to be co-doped with cobalt and neodymium (Nd). Optionally, the SAC may be cobalt-doped zinc selenide (Co 2+ :ZnSe). Optionally, the GMC may be a ceramic cobalt-doped crystalline material.

[0054] Optionally, the initial transmittance (T0) of the SA is between 75% and 90%. Optionally, the initial transmittance of the SA is between 78% and 82%.

[0055] The wavelength emitted by the laser depends on the materials used in its construction, particularly the GMC and SAC materials and dopants. Example output wavelengths include wavelengths in the range of 1,300 nm and 1,500 nm. More specific examples include 1.32 μm or approximately 1.32 μm (e.g., 1.32 μm±3 nm), 1.34 μm or approximately 1.34 μm (e.g., 1.34 μm±3 nm), and 1.44 μm or approximately 1.44 μm (e.g., 1.44 μm±3 nm). A corresponding imager sensitive to one or more of these optical frequency ranges may be included in the SWIR optical system 100 (e.g., as illustrated in FIG. 5).

[0056] 3 and 4 are schematic functional diagrams illustrating a SWIR optical system 100, in accordance with an embodiment of the disclosed subject matter. As illustrated in these figures, the laser 200 may include additional components in addition to those described above, such as, but not limited to, the following: a. A light source, such as a flash lamp 216 or laser diode 218, that acts as a pump for the laser; b. focusing optics 220 (e.g., lens) for focusing light from a light source (e.g., photodiode 218) onto the optical axis of the laser 200; c. A diffuser or other optics 222 for manipulating the laser beam 212 after it exits the optical cavity 206.

[0057] Optionally, as shown in Figure 5, SWIR optical system 100 may include optics 110 for spreading the laser over a wider FOV to improve eye safety hazards in the FOV. Optionally, SWIR optical system 100 may include optics 112 for collecting reflected laser light from the FOV and directing it onto sensor 102, for example, onto photodetector array (PDA) 108. Optionally, P-QS laser 200 is a diode pumped solid state laser (DPSSL).

[0058] Optionally, P-QS laser 200 includes at least one diode-pumped light source 218 and optics 220 for focusing light from the diode-pumped light source into an optical resonator (optical cavity). Optionally, the light source is positioned on the optical axis (as an end pump). Optionally, the light source may be rigidly coupled to high-reflectivity mirror 208 or SA 204 so that the light source is part of a monolithic microchip P-QS laser. Optionally, the laser's light source may include one or more vertical-cavity surface-emitting laser (VCSEL) arrays. Optionally, P-QS laser 200 includes at least one VCSEL array and optics for focusing light from the VCSEL array into the optical cavity. The wavelength emitted by the light source (e.g., laser pump) may depend on the crystalline material and / or dopants used in the laser. Some exemplary excitation wavelengths that can be emitted by the pump include 808 nm or about 808 nm, 869 nm or about 869 nm.

[0059] The power of a laser may depend on the application for which the laser is designed. For example, the laser output power may be between 1 W and 5 W. For example, the laser output power may be between 5 W and 15 W. For example, the laser output power may be between 15 W and 50 W. For example, the laser output power may be between 50 W and 200 W. For example, the laser output power may be greater than 200 W.

[0060] The P-QS laser 200 is a pulsed laser and may have various frequencies (repetition rates), various pulse energies, and various pulse durations. These may depend on the application for which the laser is designed. For example, the repetition rate of the laser may be 10 Hz to 50 Hz. For example, the repetition rate of the laser may be 50 Hz to 150 Hz. For example, the pulse energy of the laser may be 0.1 mJ to 1 mJ. For example, the pulse energy of the laser may be 1 mJ to 2 mJ. For example, the pulse energy of the laser may be 2 mJ to 5 mJ. For example, the pulse energy of the laser may be greater than 5 mJ. For example, the pulse duration of the laser may be 10 ns to 100 ns. For example, the pulse duration of the laser may be 0.1 μs to 100 μs. For example, the pulse width of the laser may be 100 μs to 1 ms. The size of the laser may also vary, for example, depending on the size of its components. For example, the dimensions of the laser may be X1 x X2 x X3, with each of the dimensions (X1, X2, and X3) being 10 mm to 100 mm, 20 mm to 200 mm, etc. The output coupling mirror may be flat, curved, or slightly curved.

[0061] Optionally, laser 200 may further include undoped YAG in addition to the gain medium and SA to prevent heat buildup in the absorbing regions of the gain medium. The undoped YAG may optionally be formed as a cylinder (e.g., a concentric cylinder) surrounding the gain medium and SA.

[0062] 6A is a flowchart illustrating an example of a method 600 in accordance with the presently disclosed subject matter. Method 600 is a method for fabricating components for a P-QS laser, such as, but not limited to, P-QS laser 200 described above. Referring to the set of examples described with respect to the previous figures, the P-QS laser may be laser 200. It should be noted that any variations discussed with respect to laser 200, or components thereof, may also be implemented with respect to a P-QS laser, or its corresponding components, whose components are fabricated with method 600, and vice versa.

[0063] Method 600 begins at step 602 with inserting at least one first powder into a first mold. In method 600, the at least one first powder is then processed to obtain a first crystalline material. The first crystalline material functions as either the GM or SA of the P-QS laser. In some embodiments, the gain medium of the laser is fabricated first (e.g., by sintering), and the SA is subsequently fabricated (e.g., by sintering) on ​​top of the previously fabricated GM. In other embodiments, the SA of the laser is fabricated first, and the GM is subsequently fabricated on top of the previously fabricated SA. In still other embodiments, the SA and GM are fabricated independently of each other and then bonded to form a single rigid body. Bonding may occur as part of the heating, sintering, or subsequent steps.

[0064] Step 604 of method 600 includes inserting at least one second powder, different from the at least one first powder, into a second mold. In method 600, the at least one second powder is then processed to obtain a second crystalline material. The second crystalline material functions as either the GM or SA of the P-QS laser (such that one of the SA and GM is made from the first crystalline material and the other functional portion is made from the second crystalline material).

[0065] The second mold may be different from the first mold. Alternatively, the second mold may be the same as the first mold. In such a case, the at least one second powder may be inserted, for example, above the at least one first powder (or above the first green body if it has already been made), next to the at least one first powder, or around the at least one first powder. The step of inserting the at least one second powder into the same mold as the at least one first powder (if performed) may be performed before processing the at least one first powder into the first green body, after processing the at least one first powder into the first green body, or while processing the at least one first powder into the first green body.

[0066] The first and / or second powders may be milled YAG (or any of the other previously mentioned materials, such as spinel, MgAl2O4, ZnSe, etc.) and a doping material (e.g., N 3+ , V 3+ The first powder and / or the second powder may include a raw material of YAG (or any of the other aforementioned materials, such as spinel, MgAl2O4, ZnSe, etc.) and a doping material (e.g., N 3+ , V 3+ , Co).

[0067] Step 606 is performed after step 602 and includes compressing at least one first powder in a first mold to obtain a first green body. Step 604 is performed after step 608 and includes compressing at least one second powder in a second mold to obtain a second green body. If the at least one first powder and the at least one second powder are inserted into the same mold in steps 602 and 604, the powder compression steps in steps 606 and 608 may be performed simultaneously (e.g., pressing the at least one second powder, thereby compressing the at least one first powder toward the mold), but this is not necessarily the case. For example, step 604 (and therefore step 608) may optionally be performed after the compression step of step 606.

[0068] Step 610 includes heating the first green body to obtain a first crystalline material. Step 612 includes heating the second green body to obtain a second crystalline material. In various embodiments, heating of the first crystalline material may be performed before each of steps 606 and 610, simultaneously with each of steps 606 and 610, partially simultaneously with each of steps 606 and 610, or after each of steps 606 and 610. Step 614 includes bonding a second crystalline material to the first crystalline material.

[0069] Optionally, heating the first green body in step 610 precedes compressing at least one second powder in step 608 (and possibly also inserting at least one second powder in step 604). The first and second green bodies may be heated separately (e.g., at different times, at different temperatures, for different durations). The first and second green bodies may be heated together (e.g., in the same furnace) and may or may not be connected to each other during heating. The first and second green bodies may be subjected to different heating regimes. These heating regimes may include partial co-heating and other portions of the heating regime where the bodies are heated separately. For example, one or both of the first and second green bodies may be heated separately from the other, and then the two green bodies may be heated together (e.g., after the bonding step, but this is not required). Optionally, heating the first green body and heating the second green body include simultaneously heating the first green body and the second green body in a single furnace. Note that, optionally, the bonding step of Step 614 is a result of simultaneously heating both green bodies in a single furnace. Also, note that, optionally, the bonding step of Step 614 is performed by co-sintering both green bodies after they are physically connected to each other.

[0070] Step 614 includes bonding the second crystalline material to the first crystalline material. The bonding step may be performed by any bonding method known in the art, some non-limiting examples of which are described above with respect to P-QS laser 200. Note that the bonding step may have multiple substeps, some of which may be associated with various of steps 606, 608, 610, and 612 in various ways in different embodiments. The bonding step results in a single rigid crystalline body containing both the GM and the SA.

[0071] It should be noted that method 600 may include additional steps used in the production of crystals (particularly in the production of ceramic or non-ceramic polycrystalline crystalline compounds of bounded polycrystalline materials), a few non-limiting examples of which include powder preparation, binder burn-out, densification, annealing, polishing (if necessary, as described below), etc.

[0072] The GM of the P-QS laser in method 600 (which, as previously described, can be either the first crystalline material or the second crystalline material) is a neodymium-doped crystalline material. The SA of the P-QS laser in method 600 (which, as previously described, can be either the first crystalline material or the second crystalline material) is (a) a neodymium-doped crystalline material; and (b) Trivalent vanadium-doped yttrium aluminum garnet (V 3+ a doped crystalline material selected from the group of doped crystalline materials consisting of: YAG) and cobalt-doped crystalline materials; At least one of the GM and SA is a ceramic crystalline material. Optionally, both the GM and SA are ceramic crystalline materials. Optionally, at least one of the GM and SA is a polycrystalline material. Optionally, both the GM and SA are polycrystalline materials.

[0073] Additional steps in the manufacturing process may occur during various stages of method 600, but in particular, polishing the first material before joining the second material in a sintering process is not required in at least some of these implementations.

[0074] Referring to the combinations of crystalline materials from which the GMC and SAC may be made in method 600, such combinations may include: a. GMC is ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG), and SAC is (a) ceramic trivalent vanadium-doped yttrium aluminum garnet (V 3+ In this alternative, both the Nd:YAG and the SAC selected from the group mentioned above are in ceramic form. The cobalt-doped crystalline material is a crystalline material doped with cobalt. Examples include cobalt-doped spinel (Co:Spinel, or Co 2+ :MgAl2O4), cobalt-doped zinc selenide (Co 2+ :ZnSe). Although not necessarily, the high reflectivity mirror and output coupler in this option may optionally be rigidly connected to the GM and SA such that the P-QS laser is a monolithic microchip P-QS laser. b. GMC is ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG), and SAC is (a) trivalent vanadium-doped yttrium aluminum garnet (V 3+ and (b) a non-ceramic SAC selected from the group of doped ceramic materials consisting of (Ir: YAG) and (C: YAG) and cobalt-doped crystalline materials. In such a case, a high-reflectivity mirror and output coupler are rigidly connected to the GM and SA such that the P-QS laser becomes a monolithic microchip P-QS laser. c. Ceramic neodymium-doped rare earth element crystalline material, GMC, and SAC are (a) trivalent vanadium-doped yttrium aluminum garnet (V3+ (b) a ceramic crystalline material selected from the group of doped crystalline materials consisting of (a) YAG (YAG), and (b) cobalt-doped crystalline materials. Although not required, the high reflectivity mirror and output coupler in this option may optionally be rigidly connected to the GM and SA such that the P-QS laser is a monolithic microchip P-QS laser.

[0075] It should be noted that, referring to method 600 as a whole, optionally, one or both of the SAC and GMC (and optionally, one or more intermediate connector crystalline materials, if any) are transparent to the relevant wavelengths (e.g., SWIR radiation).

[0076] 6B and 6C include some conceptual timelines for the performance of method 600, according to embodiments of the presently disclosed subject matter. To simplify the drawings, it is assumed that the SA is the result of processing at least one first powder, and the gain medium is the result of processing at least one second powder. As mentioned above, these roles may be reversed.

[0077] 7 and 8 are exploded perspective projections of a gain medium amplifier (GMA) 700 and a gain medium amplifier 800, according to embodiments of the presently disclosed subject matter. GMA 700 includes at least a neodymium-doped yttrium aluminum garnet (Nd:YAG) flat crystal 702. Crystal 702 has an average thickness of less than 5 millimeters (e.g., about 1 millimeter; further examples are provided below), but at least one of the other dimensions of crystal 702 is longer (e.g., at least 5 times longer), and in some cases, both of the dimensions perpendicular (to the average thickness) are at least 5 times longer than the average thickness of crystal 702.

[0078] The Nd:YAG flat crystal 702 includes at least the following: Top surface 704. Pump light having a first frequency (also referred to as the "pump frequency") is incident on the Nd:YAG flat crystal 702 through the top surface 704 (eg, from an optional pump light source 706). Bottom surface 708. The bottom surface 708 faces the top surface 704. First side 710. Incident laser light having a second frequency (eg, coming from optional seed laser 902) enters the Nd:YAG flat crystal through first side 710. Second side surface 712. The outgoing laser light having the second frequency is emitted from the Nd:YAG flat crystal through the second side surface 712 after being reflected by a plurality of different side surfaces of the Nd:YAG flat crystal.

[0079] According to some embodiments of the present disclosure, the power of the output laser light, after amplification with pump light, is at least 4 times stronger than the power of the input laser light. Amplification levels of at least 5, at least 7, at least 10, at least 15, at least 20, at least 30, etc. may also be implemented.

[0080] The Nd:YAG flat crystal may include additional sides in addition to the surfaces described above. Some or all of the surfaces of the Nd:YAG flat crystal (optionally including one or both of the first and second sides) may be flat or substantially flat, but this is not necessarily so, and curved surfaces may also be implemented. Light may be internally reflected from one or both of the first and second sides within the Nd:YAG flat crystal, but this is not necessarily so. Light may also be internally reflected from one or more surfaces within the Nd:YAG flat crystal other than the first and second sides, but this is not necessarily so. The first and second sides may be parallel to each other, but this is not necessarily so.

[0081] It should be noted that the terms "top" and "bottom" are arbitrary terms used to distinguish between opposing surfaces, and that these surfaces may be oriented in various ways in various embodiments of the present disclosure. The top surface may be parallel to the bottom surface (e.g., as shown in the figures), but this is not necessarily so. The first side surface may share at least one edge with the top surface and / or the bottom surface, but this is not necessarily so. Additionally, the second side surface may share at least one edge with the top surface and / or the bottom surface, but this is not necessarily so. It should be noted that any combination of the above optional implementations may be implemented, even if not explicitly stated for the sake of brevity.

[0082] The number of internal reflections that light undergoes within the Nd:YAG flat crystal 702 before being emitted as output laser light affects the gain of the GMA 700. This is exponentially related to the distance the light travels within the doped crystal. Optionally, similar to GMA 800, the optical path of the incident laser light before being emitted as output laser light includes at least 10 internal reflections 802. Various numbers of internal reflections may be implemented, such as between 10 and 15, between 15 and 20, between 20 and 25, between 25 and 35, or more. Optionally, the optical path of the incident laser light before being emitted as output laser light is at least 50 times the average thickness of the Nd:YAG flat crystal. Various ratios between the optical path and the average thickness may be implemented, such as between 50 and 100, between 100 and 200, or more than 200.

[0083] It should be noted that, optionally, GMA 700 may include one or more mirrors disposed adjacent to part (or all) of at least one side of Nd:YAG flat crystal 702, in which case the aforementioned internal reflections may include reflections from each of the one or more mirrors associated with each side of Nd:YAG flat crystal 702 instead of (or in addition to) internal reflections from each side within Nd:YAG flat crystal 702 itself. Examples of such additional mirrors are provided in FIGS. 11A-11C. For example, such mirrors may be disposed adjacent to first side 710 and / or second side 712. Although not required, the mirrors that reflect (at different angles) light coming from the Nd:YAG flat crystal 702 back into the Nd:YAG flat crystal 702 may be parallel to the respective side to which they are placed, or may be slightly angled (e.g., less than 1°) relative to the respective side. Such an angle between the mirrors may reduce undesirable effects such as parasitic lasing.

[0084] Nd:YAG flat crystals can be used to amplify specific frequencies. The pump light may have one or more pump frequencies (or pump frequency ranges). For example, the pump frequency may be 750 nanometers (nm) to 850 nm. For example, the pump frequency may be 780 nm to 830 nm. For example, the pump frequency may be 800 nm to 850 nm. For example, the pump frequency may be 800 nm to 820 nm. For example, the pump frequency may be 808 nm ± 2 nm. However, other frequency ranges may be implemented. The pump light may be laser light (e.g., a vertical cavity surface emitting laser or any other type of laser), light emitting diode (LED) light, or light from any other suitable source.

[0085] The emitted laser light may have one or more emitted light frequencies (or emitter frequency ranges). For example, the emitted light frequency may be between 1,300 nm and 1,400 nm. For example, the emitted light frequency may be between 1,310 nm and 1,370 nm. For example, the emitted light frequency may be between 1,330 nm and 1,350 nm. For example, the emitted light frequency may be 1,340 nm ±2 nm.

[0086] The second laser frequency (also referred to as the "incident laser frequency") may be the same frequency as the output laser frequency. For example, the second optical frequency may be 1,300 nm to 1,400 nm. For example, the second optical frequency may be 1,310 nm to 1,370 nm. For example, the second optical frequency may be 1,330 nm to 1,350 nm. For example, the second optical frequency may be 1,340 nm ± 2 nm.

[0087] The top surface 704 has a first dimension (e.g., length) and a second dimension (e.g., width) orthogonal to the first dimension. The first dimension is at least five times the average thickness of the Nd:YAG flat crystal. For example, if the average thickness of the Nd:YAG flat crystal is 1 mm, the first dimension may be any length greater than or equal to 5 mm (e.g., 5 mm, 10 mm, between 5 and 15 mm, between 15 and 25 mm, etc.). The average thickness may vary depending on the application, e.g., less than 0.5 mm, between 0.5 and 1 mm, between 1 and 1.5 mm, between 1.5 and 2 mm, between 2 and 5 mm, etc. The length of the Nd:YAG flat crystal is its largest measurement along the first dimension. Optionally, the average length along the first dimension may be at least several times longer than the average thickness of the Nd:YAG flat crystal.

[0088] Optionally, the Nd:YAG flat crystal 702 is a prism. Optionally, the Nd:YAG flat crystal 702 is a right prism. Optionally, the Nd:YAG flat crystal 702 is a right rectangular prism. Any other shape or configuration may be possible. One or more of any of the aforementioned surfaces of the Nd:YAG flat crystal 702 may be facets. In the example of FIG. 7 , the thickness of the Nd:YAG flat crystal 702 is substantially constant and is indicated as “H.” In the example of FIG. 7 , internal reflections within the Nd:YAG flat crystal 702 are reflected only from the first side 710 and the second side 712, but this need not necessarily be the case; light may be internally reflected from any surface of the Nd:YAG flat crystal 702 before being emitted as output laser light.

[0089] In addition to the Nd:YAG flat crystal 702, the GMA 700 may also optionally include an optional pump light source 706. The optional pump light source 706 emits pump light having at least the first frequency. The optional pump light source 706 may be implemented as any suitable type of light source, such as an LED, a vertical cavity surface emitting laser (VCSEL), or other type of laser.

[0090] It should be noted that the use of a VCSEL as a pump source (enabled by the novel geometric format of the Nd:YAG flat crystal 702 of the present disclosure) can be used to reduce the cost of the crystal amplifier compared to prior art solutions, as well as facilitate easier and higher volume manufacturing compared to prior art solutions.

[0091] The novel geometry of the present disclosure, in which pump light is delivered over a large top surface, means that the brightness per unit area of ​​the light source can be relatively low.

[0092] Optionally, GMA 700 (or GMA 800) is operated at a low duty cycle (e.g., less than 3%, between 3% and 5%, between 5% and 10%) to allow GMA 700 to cool (which is facilitated by the relative thinness of GMA 700). Optionally, GMA 700 may include a cooling module 720 (whether an active cooling module or a passive cooling module that may be connected to a heat sink) for cooling Nd:YAG flat crystal 702 or any other portion of GMA 700. Optionally, a surface of cooling module 720 may contact a corresponding surface of Nd:YAG flat crystal 702 (e.g., bottom surface 708 as shown, or any other surface of the crystal). Additionally, the relative thinness of Nd:YAG flat crystal 702 allows for doping of the crystal at a relatively high doping density (e.g., greater than 1%, between 1 and 2%, between 2 and 3%).

[0093] Optionally, GMA 700 may be a side-pumped GMA that is activated in a multimode mode, optionally in dozens of different modes of illumination.

[0094] Referring to the GMA700 (or GMA800) as a whole, better extraction efficiency can be achieved in the GMA700 by combining an Nd:YAG ceramic crystal and multiple passes of light within the Nd:YAG ceramic crystal (which extends the effective path).

[0095] Optionally, a doping concentration of neodymium in the Nd:YAG flat crystal is less than 4%. Optionally, a doping concentration of neodymium in the Nd:YAG flat crystal is between 1% and 2%. Optionally, the top surface is anti-reflective coated for at least one of the first frequency, the second frequency, and the emitted light frequency.

[0096] Optionally, the top surface is anti-reflective coated for at least two of the first frequency, the second frequency, and the emitted optical frequency. Optionally, at least one of the first side surface and the second side surface is anti-reflective coated for at least one of the first frequency, the second frequency, and the emitted optical frequency.

[0097] Optionally, at least one of the first and second sides is anti-reflective coated for at least two of the first frequency, the second frequency, and the emitted light frequency, and optionally, the at least one of the first and second sides is further anti-reflective coated for the amplified spontaneous emission (ASE) frequency of the Nd:YAG flat crystal 702 (e.g., 1,064 nm).

[0098] Optionally, light entering the Nd:YAG flat crystal through a first side is emitted along at least 80% of its optical path before being emitted through a second side.

[0099] 9 and 10 show exemplary exploded perspective projections of a gain medium amplifier and amplified laser radiation source according to embodiments of the presently disclosed subject matter. The amplified laser radiation source of FIGS. 9 and 10 may include a gain medium amplifier 700 and a seed laser 902. Optionally, the seed laser may be a Nd:YAG-based laser that emits light incident on a first side of an Nd:YAG flat crystal. Optionally, any of the lasers previously described (e.g., the lasers discussed with respect to FIGS. 1-6) may be used as the seed laser 902.

[0100] Optionally, the Nd:YAG flat crystal 702 may be a co-doped crystal in which the YAG crystal (or at least one or more portions thereof) is doped with neodymium and further doped with an additional material. The additional material may be a material that, when doped with the YAG crystal, suppresses light at at least one ASE frequency of the Nd:YAG flat crystal 702. For example, chromium (Cr), and particularly chromium ions (e.g., Cr 4+ ) may be used to suppress the 1,064 nm emission. Further doping of the Nd:YAG flat crystal 702 with chromium can improve the amplifier yield. Also, other materials (e.g., Co 3+ ) may also be used.

[0101] It should be noted that when referring to implementations in which some or all of the side surfaces are not perpendicular to the top surface, an angle between the side surfaces and the top surface (and / or bottom surface) can be selected that reduces the effect of ASE and the degree to which ASE is amplified within the Nd:YAG flat crystal 702.

[0102] 11A, 11B, and 11C are schematic functional block diagrams illustrating an exemplary MOPA system in accordance with the subject matter of this disclosure. Laser module 1100′, laser module 1100″, and laser module 1100′″ may be considered “consolidated” MOPA laser modules in that they are assembled from multiple components that may be attached to a single chassis, frame, skeleton, base, or structure and combined into a single rigid unit.

[0103] A MOPA laser module such as module 1100', module 1100'', or module 1100''' includes at least the following components: a. Prefabricated Chassis 1110. The prefabricated chassis 1110 includes multiple surfaces (e.g., holes, grooves, indentations, pins, ridges, bulges, etc.) to which other components of the MOPA laser module may be attached, connected, secured, or fastened. The prefabricated chassis 1110 may be manufactured as a single monolithic unit (e.g., using casting, milling, or any other suitable process) or as multiple parts or elements permanently affixed to each other (e.g., using gluing, welding, bonding, or any other suitable process). The prefabricated chassis 1110 may also be considered a rigid frame to which other components may be affixed when manufactured in a frame-like shape. The chassis 1110 (also referred to as a "monolithic assembly") may be composed of one or more machined pieces of material in contact with each other with high precision. Optionally, the chassis 1110 may be made of high-grade materials. Optionally, chassis 1110 may be made of one or more materials with low thermal expansion. Optionally, chassis 1110 may be made of suitable material(s) and may optionally have a shape designed to reduce and compensate for acoustic or vibration noise. The monolithic assembly may consist of multiple polishing surfaces, providing multiple parallel polishing surfaces, including at least a first polishing surface and a second polishing surface. This allows all additional elements to be aligned with each other such that angular shifts (e.g., parallelism, squareness), displacements, or any other dimensional tolerances are determined by monolith accuracy, where possible, to reduce or avoid the use of alignment tools and test equipment. In this way, the monolithic assembly may reduce costs, assembly time, qualification phases, and validation phases; b. Master oscillator (MO) laser (or simply "MO") 1120. The MO laser 1120 is permanently affixed to a first surface of at least one of a plurality of surfaces, places, spaces, locations, spots, or positions of the chassis 1110. Optionally, the MO 1120 may be a passive Q-switched laser, such as any of the Q-switched lasers discussed above (e.g., Q-switched laser 200 of FIG. 1), or any other suitable laser. The MO laser 1120 may be a SWIR laser, although this is not required. The MO laser 1120 may include, for example, a pump 1106, a GM 1108, an SA 1109, an output coupler (OC) 1112, a focusing lens 1114, a mirror 1116, one or more heat sinks 1118, and one or more thermoelectric coolers (TECs) 1122. The MO laser 1120 may include any other elements, modules, or objects; c. Power amplifier (PA) 1130. The PA 1130 is permanently affixed to at least one second surface of the plurality of surfaces, locations, spaces, positions, spots, or arrangements of the chassis 1110. Optionally, the PA 1130 may be a GMA, such as any of the gain medium amplifiers described above, or any other suitable PA. Although not necessarily, the PA 1130 may be a SWIR PA. Various amplification levels (e.g., ×2, ×5, ×10, ×25 amplification, or any other amplification level) may be implemented based on the particular application for which the MOPA laser module is designed. The PA 1130 includes at least one pump 1132, a flat crystal 1134, a mirror 1136, a TEC 1128, and a heat sink 1139. The PA 1130 may include any other elements, modules, or objects; d. Beam transfer system (BTS) 1140. The BTS 1140 is permanently affixed to the prefabricated chassis 1110 (e.g., to at least a third surface of the surfaces of the chassis 1110). The BTS 1140 includes at least a number of optical elements cooperatively operable to transfer light output from the MO 1120 (possibly after beam steering or any other optical manipulation of the transferred light) to the PA 1130 for amplification.

[0104] Although not required, the MOPA laser module may include a beam shaper 1150 for shaping the beam of light output by the PA 1130 .

[0105] In the context of this disclosure, "enduring affixing" refers to a affixing, fixing, mounting, fastening, or pinning that continues for an extended period of time without significant change. The permanent affixing can be a direct affixing (e.g., by pressing one of two objects toward the other without an intermediate component), an affixing using an affixing medium (e.g., adhesive, screws, etc.), an indirect affixing (e.g., via a spacer or bracket), etc. The permanent affixing can be a rigid affixing, but optionally, a controllably alterable affixing. For example, two objects of a MOPA laser module can be permanently affixed to each other by an intermediate mechanical coupler, the dimensions and / or position of which can be controllably altered by a controller (e.g., by changing the magnitude of the current supplied to the intermediate mechanical coupler).

[0106] Alignment between the components of the MOPA laser module 1100′, the MOPA laser module 1100″, or the MOPA laser module 1100′″ is primarily determined by the spatial relationship between the surfaces of the prefabricated chassis 1110 and / or the spatial relationship between elements or objects affixed to the surfaces. For example, the spatial relationship between at least one first surface and at least one second surface determines the alignment between the MO 1120 and the PA 1130. For example, as shown in FIG. 11C , the MOPA laser module 1100′″ may include multiple portions or surfaces of a chassis (designated 1160), each of which may extend outside the plane of the chassis next to it, may be a recess or groove deeper than the plane of the chassis surrounding it, or may be flush with the plane of the chassis surrounding it. Those skilled in the art will understand that the height of each portion or surface of the chassis 1160 may be the same height or a different height than the height of another portion or surface of the chassis 1160. It should be noted that, for example, some of the first, second, and third surfaces may be portions of a flat surface of the chassis. For example, during the assembly process, the position of some components of the MOPA laser module 1100''' may be determined by pressing each component against a protrusion and adhering it to a flat surface of the chassis 1110 that is underneath the object.

[0107] FIG. 12 is a side view illustrating example components of a MOPA laser module and chassis in accordance with the subject matter of this disclosure. The MOPA laser module may be, for example, module 1100′, module 1100″, or module 1100′″. The side view of FIG. 12 illustrates how various components of the MOPA laser module may be connected to chassis 1110. It should be understood that any element, component, or device may be connected or affixed to chassis 1110. In the illustrated example, the pump (e.g., pump 1106 in FIG. 11C ) is positioned within a dedicated hole or groove, and the OC (e.g., OC 1112 in FIG. 11C ) and lens (e.g., lens of BTS 1140 in FIG. 11C ) are positioned to abut protrusions on the surface of chassis 1110. According to an embodiment, one or more elements or components may be integrally formed with chassis 1110. For example, a mirror of PA 1130 (eg, one of mirrors 1136) is made from a protruding portion of chassis 1110 that has been polished to include a highly reflective surface that can function as mirror 1136.

[0108] For example, if PA 1130 includes at least one pump and a flat crystal 1134 (e.g., having an average thickness of less than 20 millimeters) that is excited by the pump such that MO 1120 light passing through the crystal 1134 in multiple passes is amplified in each of the multiple passes with the energy of the pump, chassis 1110 may optionally include at least one polished surface that acts as a mirror 1136 that reflects light from the flat crystal at least once back into crystal 1134. Such a mirror surface may be integral with chassis 1110, made from the same material, cast together, etc.

[0109] Optionally, affixing both the MO 1120 and PA 1130 to the same chassis 1110 (e.g., the same rigid plate) can be used to align critical surfaces so that multiple surfaces can be aligned with one another with minimal tolerance. Crucial surfaces are surfaces of components of the MOPA laser module whose spatial relationships require high precision to produce high-quality light output. Such critical surfaces can include, for example, mirror flats, lens axes, prism placement, etc. Permanently affixing such components to the chassis 1110 (e.g., directly or indirectly, as described in further detail below) can also be used to maintain alignment between these components over time in harsh environments and / or under various conditions (e.g., temperature, humidity).

[0110] The inclusion of such multiple surfaces as part of the chassis 1110 (particularly when polished prior to the process of attaching the components to the chassis) can be utilized to align such additional components with one another, where possible, such that angular shift (e.g., parallelism, squareness), displacement, or any other dimensional tolerance is dictated by the precision with which the chassis can be manufactured and machined.

[0111] In some embodiments of the present disclosure, the MOPA laser module may include one or more TECs (e.g., TEC 1122, TEC 1128 in FIG. 11A ) located where cooling is required (e.g., as illustrated in the figures). Optionally, such one or more TECs may be embedded in the chassis 1110 to allow active temperature control of the entire chassis 1110 or separate areas or modules within the chassis 1110. Optionally, at least a portion of the chassis 1110 is part of a TEC operable to cool at least one of the MO 1120 and the PA 1130.

[0112] Optionally, a MOPA laser module such as 1100′, 1100″, or 1100′″ may include at least one lens and bending optics (e.g., as part of the BTS 1140). The optical axis of light output by the MO 1120 continues to a position on the entrance position on the side of the PA 1130, such that light incident on the optical axis into the PA 1130 is amplified and emitted at the output optical axis of the PA 1130. That is, even when the BTS 1140 is not assembled, the alignment between the MO 1120 and the PA 1130 can be verified (at least to some extent) by measuring the output of the PA 1130 when its optical entrance window is directly illuminated by the MO 1120. Optionally, the BTS 1140 maintains this optical axis. Optionally, the BTS 1140 is positioned relative to the chassis 1110 such that light enters the BTS 1140 along the optical axis described above, is deflected by the bending optics and manipulated by at least one lens, and then exits the BTS 1140 along the optical axis. Optionally, the BTS 1140 may be part of the chassis 1110, for example, integrated with the chassis 1110, such that all optical elements of the BTS 1140 are attached, glued, or fixed directly to the chassis 1110 with no additional intermediate components. This increases tolerances and reduces costs.

[0113] Optionally, the MOPA laser module, such as 1100', 1100" or 1100'" is a SWIR MOPA laser module, a. The frequency of the MO pump source is 750 nanometers (nm) to 850 nm; b. The frequency of light emitted by MO is 1,300 nm to 1,400 nm; c. The frequency of the pump source of the PA is 750 nanometers (nm) to 850 nm; d. The frequency of the light emitted by the PA is 1,300 nm to 1,400 nm; The gain medium of the e.MO comprises a crystalline material (ceramic or not) that is neodymium-doped yttrium aluminum garnet (Nd:YAG); f.MO saturable absorber is (a) Trivalent vanadium-doped yttrium aluminum garnet (V 3+ :YAG) and (b) Divalent cobalt-doped crystalline material a crystalline material (ceramic or not) selected from the group of doped ceramic materials consisting of: g. PA includes a Nd:YAG flat crystal; It may also be a SWIR MOPA laser module.

[0114] The disclosed design of a MOPA laser module such as 1100', 1100", or 1100'" may be preferable to various prior art solutions (e.g., fiber-coupled power amplifiers) in that it requires a minimal number of elements, alignment tools, and test equipment, thereby reducing costs, assembly time, and qualification and verification phases. For example, a master oscillator fiber amplifier (MOFA) requires precise and highly efficient coupling from a (solid-state) laser to a single / multimode fiber. For high-power sources, the spatial shape of the laser is not a simple TEM00 mode, making coupling very challenging and requiring complex beam-shaping optics, precise micropositioning, and active / passive stabilizers. In contrast, the presented design is less sensitive (e.g., unaffected) by these aspects and is inherently precise, thereby reducing costs, assembly time, qualification, and verification phases.

[0115] The MO 1120 may include any combination of one or more of the following components: a. A pump source (e.g., at 808 nm); b. Pump beam shaping lens; c. an active material (e.g., Nd:YAG); d. A saturable absorber (e.g., made of V:YAG); e. Output coupler (OC); f. Heat sink; g.TEC.

[0116] The beam delivery system (BTS) 1140 may include any combination of one or more of the following components: a. Lens; b. Folding elements (mirrors, prisms).

[0117] The power amplifier (PA) 1130 may include any combination of one or more of the following components: a. Mirror 1 (e.g., M1 in Figure 11B); b. Mirror 2 (e.g., M2 in Figure 11B); c. Active material (slab) (e.g., made of Nd:YAG); d. A pump source (e.g., at 808 nm); e. Pump beam shaping lens; f. Heat sink; g.TEC.

[0118] It should be noted that when referring to any pump of a MOPA laser module such as 1100', 1100" or 1100'", either end pumping or side pumping may be implemented for the MO 1120 and / or PA 1130, and the pump may be positioned in any suitable orientation relative to the associated crystal.

[0119] Reference is now made to Figures 13A-13E, which illustrate BTSs such as BTS 1140, according to embodiments of the presently disclosed subject matter. For convenience, these exemplary BTSs are numbered 1300a, 1300b, 1300c, 1300d, and 1300e. The BTSs of Figures 13A-13E may be used as BTS 1140 for a MOPA laser module, but are not limited to use in such a MOPA laser module and may be used in any suitable MOPA laser module. The BTS may include a chassis 1320, such as any of the chassis of Figures 11A-11C.

[0120] 13A-13D, by way of example only, a BTS for a MOPA laser module is disclosed, which BTS includes at least the following: a. an optical inlet 1302 for receiving the optical beam of the MO laser module 1120 along an incident optical axis 1304; b. an optical exit, or outlet, 1306 for emitting the steered light beam along an output optical axis 1308 towards the PA 1130; c. A plurality of lenses 1310 (e.g., aspheric lens, cylindrical lens), at least one of which is shaped to manipulate a light beam and to fit into at least one dedicated three-dimensional (3D) structure of the chassis. The fit of the at least one lens to each dedicated 3D structure may be a direct fit or may be a fit using one or more dedicated intermediate mechanical components (e.g., spacers, brackets). d. Folded Optical System 1312, Folded Optical System 1314. The folded optical system 1312, 1314 includes multiple folded optical components including at least one component selected from the group consisting of a mirror (e.g., mirror 1312) and a prism (e.g., prism 1314). The folded optical system (1312, 1314) may be operable to deflect light entering the BTS along the incident optical axis 1304 toward at least one lens of the multiple lenses 1310 and to deflect light coming from at least one other lens of the multiple lenses 1310 toward the exit optical axis 1308. Here, at least one of the folded optical components has a shape to manipulate the light beam and to fit into at least one customized 3D structure of the chassis 1320. The fit of the at least one folded optical component to each customized 3D structure may be a direct fit or may be a fit using one or more dedicated intermediate mechanical components (e.g., spacers, brackets). It should be noted that the term "customized 3D structure" is intended to have the same meaning as "dedicated 3D structure," and these different terms are used to distinguish between 3D structures intended for lenses and 3D structures intended for folded optical components (e.g., mirrors, prisms).

[0121] Optionally, the BTS may further include at least a portion of a chassis 1320 that includes at least one dedicated 3D structure and at least one customized 3D structure. Optionally, the BTS may further include mechanical connectors (e.g., spacers, brackets, adhesives, screws, bolts, pins, welds) that connect components (e.g., lenses, mirrors, prisms) to the respective 3D structures of the chassis such that all of the lens and folded optical components of the BTS are aligned and operable to transmit the light beam from the inlet to the outlet through the multiple lenses.

[0122] In such a case, the chassis may be made from a single material with a single, machined, precise surface. Multiple, highly precise, predefined areas 1318 on the surface may include grooves, slits, slots, protrusions, ridges, trenches, or any other shape or structure in the chassis 1320. The areas or regions 1318 may be used as alignment base 3D structures for all optical elements. Other types of 3D structures may also be used.

[0123] Optionally, at least one of the folded optical components (e.g., 1312, 1314) is controllably movable by at least one other component of the BTS to adjust the position of each folded optical component (e.g., 1312, 1314) relative to each customized 3D structure.

[0124] 13B, optionally, at least one of the folded optical components is a pentaprism 1322 having four active surfaces, the pentaprism 1322 operable to internally reflect the light beam twice within the pentaprism 1322 before emitting the light beam out of the pentaprism 1322.

[0125] Optionally, at least one of the folded optical components is a retroreflector (e.g., 1314) having at least three active surfaces. The retroreflector is operable to internally reflect the light beam twice within the retroreflector before emitting the light beam out of the retroreflector. The retroreflector (e.g., 1314), pentaprism 1322, and other components can be used to align the beam, for example, angularly by rotating the retroreflector in multiple directions, or linearly by translating it in multiple directions.

[0126] The use of pentaprism 1322 and / or retroreflector 1314 as in Figures 13B-13D allows for a wider tolerance range for the angular placement of the BTS because elements 1322 and 1314 do not introduce beam angle shifts when rotated about their axes.

[0127] In some embodiments, the output optical axis may be a continuation of the input optical axis, since BTSs such as 1300a, 1300b, 1300c, 1300d, and 1300e may not affect the optical axis of the beam from MO 1120 to PA 1130. Optionally, the direction of the light beam output from the BTS may be controllably rotated so that the light beam enters PA 1130 at an optimal angle that allows maximum gain. In such cases, the angle of the output light beam may be controllably changed using any combination of one or more of the following steps: a. Rotating the entire BTS (e.g., only possible in some of the illustrated examples, but not in others); b. Rotating some or one of the elements, such as the rotating mirror 1324 in the example of Figure 13B and the parallelogram 1326 in the example of Figure 13D; or c. Rotating either the MO 1120 or the PA 1130. Rotation of the PA 1130 can be done through introducing an angle with respect to the surface or surfaces to which the MO 1120 and / or PA 1130 are aligned.

[0128] Referring to the example of Figure 13C, two pentaprisms 1322 may be used as the entrance and exit deflection optical components, and optional retroreflectors may be used for 180-degree rotation (more complex optical paths within the BTS, in which the beam direction is changed five or more times, may also be implemented). By using two pentaprisms, angular rotation of the BTS may be minimized while components of the BTS may be rotated during the assembly process. In the example of Figure 13C, the orientation of the pentaprism 1322 may be positioned in a specific orientation, although any other orientation may be used; for example, the pentaprism 1322 may be oriented vertically, which allows for high-tolerance passive maintenance or alignment.

[0129] 13D, parallelogram 1326 may be provided with a reflective coating. Parallelogram 1326 is positioned in a fixed position to allow optimal angular positioning and abuts entrance pentaprism 1322. The angle of one of the faces of parallelogram 1326 (or the entire parallelogram) may determine the rotation angle (of the output beam).

[0130] 13E , a focusing lens 1330 may be positioned at the entrance 1332 of the BTS to focus the light beam 1334 entering the BTS from the MO 1120. A plate 1336 may be positioned after the focusing lens 1330, i.e., along the path of the light beam 1334 from the MO 1120 to the PA 1130. A predetermined angle of the plate 1336 may cause a shift in the position of the beam 1334, which may be used to direct and align the beam 1334 to the PA 1130 with maximum transmission. Additionally, a wedge prism pair 1338 positioned after 1336 (along the path of the light beam 1334 from the MO 1120 to the PA 1130) may control the titling of the beam 1334 in two directions relative to the original direction of the beam 1334, for example, from the MO 1120. 13E, all elements, including MO 1120, PA 1130, focusing lens 1330, plate 1336, and prism pair 1338, are linearly positioned relative to a common wall of chassis 1340, thereby minimizing degrees of freedom and significantly reducing tolerance stackup. Any other lenses, prisms, plates, or other optical elements may be linearly positioned relative to a common wall of chassis 1340 and used to minimize degrees of freedom and reduce tolerance stackup.

[0131] 14 is a flowchart of an exemplary process for a method of fabricating a merged MOPA laser module according to some embodiments of the presently disclosed subject matter. Referring to the examples described with respect to the previous figures, method 1400 may be used to fabricate, for example, the MOPA laser module of FIGS. 11A-11C. All elements depicted in FIG. 14 may be elements described with reference to, for example, the MOPA laser module of FIGS. 11A-11C.

[0132] The method 1400 includes at least the following steps: Step 1410 permanently affixes or attaches at least one component of an MO (e.g., MO 1120 of FIG. 11A ) and at least one component of a PA (e.g., MO 1120 of FIG. 11A ) to different surfaces of a prefabricated chassis, such that a predetermined alignment between the MO and PA is determined by affixing the at least one MO component and the at least one PA component to the prefabricated chassis. For example, MO 1120 may be permanently affixed to at least one first surface of the plurality of surfaces of chassis 1110 of FIG. 11C . PA 1130 may be permanently affixed to at least one second surface of the plurality of surfaces of chassis 1110 of FIG. 11C . The alignment between the MO and PA may be determined by the spatial relationship between the at least one first surface and the at least one second surface. Step 1420, which may be performed after step 1410, may include permanently coupling or affixing a BTS to the prefabricated chassis. The BTS may be attached or affixed to at least a third surface of the plurality of surfaces of the chassis 1110. The BTS may include a plurality of optical elements for transmitting light output from the MO to the PA for amplification. Referring to the embodiments described with respect to previous figures, the BTS of step 1420 may be the BTS 1140 of FIGS. 11A-11C and / or any variation of the BTS 1320 discussed with respect to FIGS. 13A-13E.

[0133] It should be noted that fine tuning and / or further alignment of the MO components and / or PA components may be performed after some or all of the BTS components have been placed and secured to the chassis.

[0134] Optionally, the bonding step may include the steps of directing or illuminating the MO directly toward the PA, sensing an output of the PA resulting from the illumination, adjusting an alignment between the MO and the PA based on a result of the sensing step, and bonding at least one component of at least one of the MO and the PA based on the adjusted alignment.

[0135] Optionally, method 1400 may further include measuring the output of the PA at two or more different temperatures and two or more different states of at least one controllable optical component (COC) of the BTS, calculating temperature compensation information for the at least one COC, and storing the temperature compensation information in a tangible memory module readable by the controller operable to change the state of the at least one COC.

[0136] Optionally, method 1400 may further include measuring the output of the PA at two or more different temperatures and two or more different states of at least one thermoelectric cooler (TEC) of the MOPA laser module, calculating temperature compensation information for the at least one TEC, and storing the temperature compensation information in a tangible memory module readable by the controller operable to change the state of the at least one TEC.

[0137] Optionally, method 1400 may further include measuring the output of the PA at two or more different temperatures and two or more different states of at least one pump of the MO or PA, calculating temperature compensation information for the at least one pump, and storing the temperature compensation information in a tangible memory module readable by the controller operable to change the state of the at least one pump.

[0138] Optionally, the permanently bonding step may be preceded by a step of polishing at least one first surface and at least one second surface of the chassis so that they are parallel to one another, and the permanently bonding step includes a step of permanently bonding at least one component of the MO to the first surface and a step of permanently bonding at least one component of the PA to the second surface.

[0139] For step 1420, and for some optional implementations of the MOPA laser module, assembly of the BTS is separate and occurs only after the MO and PA have already been aligned (down to the angle of incidence to the PA). Several methods for precisely positioning the various elements can be used. These methods can be used for any example of positioning and / or securing members described in this disclosure: a. Rotational Alignment Invariance - Using precision prisms (e.g., pentaprisms, doves, retroreflectors) instead of regular mirrors allows for precise assembly without changing angular tolerances. b. The placement of subassemblies such as BTS does not affect the alignment of the system. c. The assembly procedure (eg, in FIG. 13A) is similar to the assembly process described for the entire MOPA laser module.

[0140] After the above steps are completed, a final testing and alignment process may optionally be initiated. The purpose of this process may be to achieve at least one of the following: a. Alignment and testing of MOPA laser modules for optimal output gain and output beam shape. b. Testing performance over the full temperature range and full TEC range. Measurements taken at various temperatures can be used, for example, by a controller to control the operation of various components of the MOPA laser module over its lifetime, as discussed elsewhere in this disclosure.

[0141] Method 1400 may optionally include any one or more of the following optional steps: a. At least one MO component (e.g., output coupler) is attached (e.g., glued) to one polished surface of the chassis so that they are parallel to each other. This attachment may be a direct connection or an indirect connection (e.g., via a chassis, bracket, spacer, etc.). b. Attaching at least one PA component (e.g., a mirror) to at least one MO component so that they are also parallel. This attachment may be a direct connection or an indirect connection (e.g., via a chassis, bracket, spacer, etc.). c. As an alternative to (a) and (b), or in conjunction with (a) and / or (b) to achieve high precision alignment (angular and / or positional), the assembly may include using assembly tools (e.g., spacers, brackets, micropositioners, autocollimators, etc.) for alignment of the surfaces or various surfaces in (a) and (b). d. Additional elements may be assembled in a manner similar to steps a-c until the MO submodule and PA submodule are assembled. Note that some components of the MO and / or PA may be connected to each other before being connected to the cassis (e.g., as described with respect to fabricating the P-QS laser of FIG. 1). e. After all elements are in place, optical alignment and testing may be performed to ensure the assembly is within specifications. Optional goals of these tests may be to achieve one or more of the following: Optimal beam quality at the i.MO exit (energy, beam and pulse shape, etc.). ii. Optimal alignment of MO to PA - entrance angle and position. f. Following stage 1420, alignment of the PA entrance angle and other parameters may be performed to optimize the gain of the MOPA laser module.

[0142] In the event that one or more of the tests performed during manufacturing (or later in the life of the MOPA laser) fails, the system may include a controller that can correct itself by modifying the TEC current, pump power, etc.

[0143] Returning to the discussion of a MOPA laser module such as module 1100′, module 1100″, or module 1100′″ (e.g., according to FIGS. 11A-11C ), it should be noted that, optionally, the MOPA laser module may include at least one intermediate mechanical coupling permanently affixed between a component of the MO or PA and a corresponding surface of the chassis, the degree of displacement caused by the intermediate mechanical coupling and the corresponding surface being determined based on optical measurements of light emitted by the MO. While such mechanical coupling may be controlled by a controller during operation of the MOPA laser module, this is not necessarily the case; optionally, the degree of displacement may be determined during manufacture of the MOPA laser module in a manner that is not alterable by the controller. For example, as a result of measurements of light intensity (or other optical parameters) performed during manufacture of the MOPA laser module, method 1400 may include selecting one of a plurality of optional mechanical couplings of various dimensions (e.g., spacers of various widths, brackets with various angles, etc.).

[0144] See Figure 1 IB. MOPA laser module 1100" may optionally include one or more internal optical sensors, e.g., sensor 1162 and / or sensor 1164, for measuring a sensed intensity indicative of the intensity of the internal light beam emitted by at least one of MO 1120 and PA 1130, and a controller 1166 operable to trigger movement of at least one optical component of the MOPA laser module to increase the intensity of the internal light beam. One or more beam splitters 1168, 1170 may be included to direct light of the light beam toward an associated internal optical sensor (which may be, for example, a photodiode).

[0145] Optionally, MOPA laser module 1100" may include one or more internal temperature sensors 1172 for measuring a temperature sensed within the MOPA laser module. According to some embodiments of the present disclosure, controller 1166 may be operable to trigger movement of at least one optical component of the MOPA laser module based on the measured temperature, for example, based on the temperature measured by temperature sensor 1172 and / or based on temperature compensation information stored in a tangible memory module accessible (directly or indirectly) by the controller.

[0146] Optionally, MOPA laser module 1100" may include one or more internal optical sensors (e.g., 1162 and 1164) for measuring a sensed intensity indicative of the intensity of the internal light beam emitted by at least one of the MO and PA, and a controller (e.g., 1166) operable to trigger electrical magnitude changes in controlled components (e.g., TEC, pump) of the MOPA laser module to increase the intensity of the internal light beam. Beam splitters (e.g., 1168, 1170) may be included to direct light of the light beam toward an associated internal optical sensor (which may be, for example, a photodiode).

[0147] Optionally, MOPA laser module 1100″ may include one or more internal temperature sensors 1172 for measuring a temperature sensed within the MOPA laser module, and a controller (e.g., 1166) operable to trigger changes in electrical magnitudes of controlled components of the MOPA laser module based on the measured temperature, e.g., a temperature measured by sensor 1172. In some embodiments, the controller (e.g., 1166) may be operable to trigger changes in electrical magnitudes of controlled components of the MOPA laser module based on the measured temperature and / or based on temperature compensation information stored in a tangible memory module accessible (directly or indirectly) by the controller.

[0148] In the claims, any reference signs placed between parentheses shall not be construed as limiting the scope of the claim. The word "comprising" does not exclude the presence of other elements or steps than those recited in a claim. Furthermore, as used herein, the words "a" or "an" are defined as one or more than one. Also, the use of introductory phrases such as "at least one" and "one or more" in the claims shall not be construed as implying that the introduction of another claim element with the indefinite article "a" or "an" limits any particular claim containing such introduced claim element to a disclosure containing only one such element, even if the same claim also contains the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "an." The same applies to the use of definite articles. Unless otherwise specified, the terms "first" and "second", etc. are used to arbitrarily distinguish between the elements designated by such terms. As such, these terms are not intended to necessarily indicate a chronological or other priority between such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

[0149] While particular configurations for the present disclosure have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all modifications and variations that fall within the true spirit of the present disclosure. It will be understood that the above-described embodiments are given by way of example, and that various configurations and combinations of these configurations are susceptible to change and modification. While various embodiments have been shown and described, there is no intention to limit the present disclosure by such disclosure. Rather, it will be understood that the intention is to cover all modifications and alternative configurations that fall within the scope of the present disclosure, as defined by the appended claims. [Brief explanation of the drawings]

[0150] [Figure 1] FIG. 1 is a schematic functional block diagram illustrating an example of a short-wave infrared (SWIR) optical system. [Figure 2A] FIG. 1 is a schematic functional block diagram illustrating an example of a P-QS laser. [Figure 2B] FIG. 1 is a schematic functional block diagram illustrating an example of a P-QS laser. [Figure 2C] FIG. 1 is a schematic functional block diagram illustrating an example of a P-QS laser. [Figure 3] FIG. 1 is a schematic functional diagram illustrating an exemplary implementation of a SWIR optical system. [Figure 4] FIG. 1 is a schematic functional diagram illustrating another exemplary implementation of a SWIR optical system. [Figure 5] FIG. 1 is a schematic functional block diagram illustrating an example of a SWIR optical system. [Figure 6A] 1 is a flowchart illustrating an example of a method for manufacturing components for a P-QS laser. [Figure 6B] Included are some conceptual timelines for carrying out the methods described above. [Figure 6C] Included are some conceptual timelines for carrying out the methods described above. [Figure 7]1 illustrates an exemplary exploded perspective view of a gain medium amplifier (GMA), according to an embodiment of the disclosed subject matter. [Figure 8] 1 illustrates an exemplary exploded perspective view of a gain medium amplifier (GMA), according to an embodiment of the disclosed subject matter. [Figure 9] 1 illustrates an exemplary exploded perspective projection of a gain medium amplifier (GMA) and amplified laser radiation source, according to an embodiment of the disclosed subject matter. [Figure 10] 1 illustrates an exemplary exploded perspective projection of a gain medium amplifier (GMA) and amplified laser radiation source, according to an embodiment of the disclosed subject matter. [Figure 11A] FIG. 1 is a schematic functional block diagram illustrating an exemplary MOPA system in accordance with the subject matter of the present disclosure. [Figure 11B] FIG. 1 is a schematic functional block diagram illustrating an exemplary MOPA system in accordance with the subject matter of the present disclosure. [Figure 11C] FIG. 1 is a schematic functional block diagram illustrating an exemplary MOPA system in accordance with the subject matter of the present disclosure. [Figure 12] 1 is a side view illustrating exemplary components and a chassis of a MOPA laser module in accordance with the subject matter of the present disclosure. [Figure 13A] 1 illustrates an exemplary beam delivery system in accordance with the subject matter of this disclosure. [Figure 13B] 1 illustrates an exemplary beam delivery system in accordance with the subject matter of this disclosure. [Figure 13C] 1 illustrates an exemplary beam delivery system in accordance with the subject matter of this disclosure. [Figure 13D] 1 illustrates an exemplary beam delivery system in accordance with the subject matter of this disclosure. [Figure 13E] 1 illustrates an exemplary beam delivery system in accordance with the subject matter of this disclosure. [Figure 14] 1 is a flowchart of an exemplary process for a method of manufacturing a merged MOPA laser module, according to some embodiments of the presently disclosed subject matter.

Claims

1. 1. A merged master oscillator power amplifier (MOPA) laser module, comprising: a prefabricated chassis including a plurality of surfaces; a master oscillator laser (MO) affixed to a first surface of at least one of said plurality of surfaces; a power amplifier (PA) affixed to a second surface of at least one of said plurality of surfaces; a beam delivery system (BTS) secured to the prefabricated chassis; Including, a spatial relationship between the at least one first surface and the at least one second surface determines an alignment between the MO and the PA; The BTS includes a combined MOPA laser module including a plurality of optical elements for transmitting light output from the MO to the PA for amplification.

2. The merged MOPA laser module of claim 1, wherein the MO is a passively Q-switched (P-QS) laser.

3. 10. The merged MOPA laser module of claim 1, wherein the MO includes a crystalline saturable absorber rigidly coupled to a crystalline gain medium of the MO.

4. 4. The merged MOPA laser module of claim 3, wherein the MO further comprises a high-reflectivity mirror and an output coupler rigidly coupled to the crystalline gain medium and the crystalline saturable absorber, such that the MO is a monolithic microchip P-QS laser.

5. 10. The merged MOPA laser module of claim 1, wherein the at least one first surface and the at least one second surface are polished surfaces parallel to each other.

6. The PA is at least one pump; a flat crystal having an average thickness of less than 20 millimeters excited by said pump; Including, the light of the MO passes through the planar crystal in a plurality of passes and is amplified in each of the plurality of passes; the prefabricated chassis includes at least one polished surface; 10. The merged MOPA laser module of claim 1, wherein at least one of the polished surfaces functions as a mirror that reflects light from the flat crystal back into the flat crystal at least once.

7. at least one lens; a folded optical system; Including, an optical axis of the light output by the MO continues to an incidence position on a side of the PA such that light incident on the PA along the optical axis is amplified and emitted at an output optical axis of the PA; 2. The merged MOPA laser module of claim 1, wherein the BTS is positioned relative to the prefabricated chassis such that light enters the BTS along the optical axis, is deflected by the bending optics and manipulated by at least one of the lenses, and then exits the BTS along the optical axis.

8. the frequency of the pump source of the MO is between 750 nanometers (nm) and 850 nm; the frequency of the light emitted by the MO is between 1,300 nm and 1,400 nm; the frequency of the PA pump source is between 750 nanometers (nm) and 850 nm; the frequency of the light emitted by the PA is between 1,300 nm and 1,400 nm; the gain medium of the MO comprises a crystalline material that is neodymium-doped yttrium aluminum garnet (Nd:YAG); The MO saturable absorber is (a) Trivalent vanadium-doped yttrium aluminum garnet (V ３＋ :YAG) and (b) Divalent cobalt-doped crystalline material and a crystalline material selected from the group of doped ceramic materials consisting of:

10. The merged MOPA laser module of claim 1, wherein the PA comprises a Nd:YAG flat crystal.

9. 10. The merged MOPA laser module of claim 1, wherein at least a portion of the prefabricated chassis is part of a thermoelectric cooler (TEC) operable to cool at least one of the MO and the PA.

10. further comprising an intermediate mechanical connection secured between a component of the MO or the PA and a corresponding surface of the prefabricated chassis; 10. The combined MOPA laser module of claim 1, wherein the degree of dislocation introduced by the intermediate mechanical joint and the corresponding surface is determined based on optical measurements of light emitted by the MO.

11. an internal optical sensor for measuring a sensed intensity indicative of the intensity of an internal light beam emitted by at least one of the MO and the PA; a controller operable to trigger movement of at least one optical component of the merged MOPA laser module to increase the intensity of the internal light beam; 10. The merged MOPA laser module of claim 1, comprising:

12. an internal temperature sensor for measuring a temperature sensed within the combined MOPA laser module; a controller operable to trigger movement of at least one optical component of the merged MOPA laser module based on the measured temperature; 10. The merged MOPA laser module of claim 1, comprising:

13. an internal optical sensor for measuring a sensed intensity indicative of the intensity of an internal light beam emitted by at least one of the MO and the PA; a controller operable to trigger electrical magnitude changes of controlled components of the merged MOPA laser module to increase the intensity of the internal light beam; 10. The merged MOPA laser module of claim 1, comprising:

14. an internal temperature sensor for measuring a temperature sensed within the combined MOPA laser module; a controller operable to trigger changes in electrical magnitudes of controlled components of the merged MOPA laser module based on the measured temperature; 10. The merged MOPA laser module of claim 1, comprising:

15. The BTS an optical entrance for receiving the optical beam of the MO laser module along an incident optical axis; an optical outlet for emitting a steered light beam along an output optical axis towards the PA; a plurality of lenses, at least one of the plurality of lenses shaped to manipulate the light beam and to conform to at least one dedicated three-dimensional (3D) structure of a chassis; a folded optics system including a plurality of folded optical components including at least one type of component selected from the group consisting of mirrors and prisms, operable to deflect light entering the BTS along the input optical axis towards at least one of the plurality of lenses and to deflect light coming from at least one other of the plurality of lenses towards the output optical axis, at least one of the folded optical components being shaped to manipulate the light beam and to conform to the at least one customized 3D structure of the chassis; 10. The merged MOPA laser module of claim 1, comprising:

16. The merged MOPA laser module of claim 15 , wherein the chassis has a chassis portion including at least one dedicated 3D structure and at least one customized 3D structure.

17. 16. The merged MOPA laser module of claim 15, wherein at least one of the plurality of bent optical components is controllably movable by at least one component of the BTS to adjust the position of each bent optical component relative to each customized 3D structure.

18. at least one of the plurality of folded optical components is a pentaprism having four active surfaces; 16. The merged MOPA laser module of claim 15, wherein the pentaprism is operable to internally reflect the light beam twice within the pentaprism before emitting the light beam out of the pentaprism.

19. at least one of the plurality of said folded optical components is a retroreflector having at least three active surfaces; 16. The merged MOPA laser module of claim 15, wherein the retroreflector is operable to internally reflect the light beam twice within the retroreflector before emitting the light beam out of the retroreflector.

20. 16. The merged MOPA laser module of claim 15, wherein the output optical axis is a continuation of the input optical axis.

21. 1. A method for manufacturing a merged master oscillator power amplifier (MOPA) laser module, comprising: affixing at least one component of a master oscillator laser (MO) and at least one component of a power amplifier (PA) to different surfaces of a prefabricated chassis; coupling a beam delivery system (BTS) to the prefabricated chassis after the step of fastening the at least one component of the MO and the at least one component of the PA; Including, the step of fastening at least one component of a motion object (MO) and at least one component of a PA (PA) to the prefabricated chassis determines alignment between the MO and the PA; The method, wherein the BTS includes a plurality of optical elements for transmitting light output from the MO to the PA for amplification.

22. The step of fixing comprises: directing the MO directly towards the PA; sensing the output of the PA resulting from illumination; adjusting the alignment between the MO and the PA based on the results of the sensing step; fixing at least one component of at least one of the MO and the PA based on the adjusted alignment; 22. The method of claim 21, comprising:

23. measuring the output power of the PA at two or more different temperatures and two or more different states of at least one controllable optical component (COC) of the BTS; calculating temperature compensation information for at least one of said COCs; storing said temperature compensation information in a tangible memory module readable by a controller operable to change the state of at least one said COC; 22. The method of claim 21 further comprising:

24. measuring the output power of the MOPA at two or more different temperatures and two or more different states of at least one thermoelectric cooler (TEC) of the MOPA laser module; calculating temperature compensation information for at least one of said TECs; storing the temperature compensation information in a tangible memory module readable by a controller operable to change the state of at least one of the TECs; 22. The method of claim 21 further comprising:

25. measuring the output of the MO or at least one pump of the PA at two or more different temperatures and two or more different conditions; calculating temperature compensation information for at least one of said pumps; storing said temperature compensation information in a tangible memory module readable by a controller operable to change the state of at least one of said pumps; 22. The method of claim 21 further comprising:

26. The step of bonding is preceded by a step of polishing at least one first surface and at least one second surface of the prefabricated chassis so that they are parallel to each other; The step of fixing comprises: affixing at least one of the components of the MO to the first surface; affixing at least one of the components of the PA to the second surface; 22. The method of claim 21, comprising:

Images