Laser amplifier utilizing multiple end pump spots and method of manufacture - Patents.com

Abstract

The present application relates to a laser amplifier system that utilizes multiple end pump spots to pump an optical crystal during the amplification process, and includes a telecentric telescope configured to expand each individual pump beamlet such that the pump beamlets remain parallel and substantially non-diverging as they enter an optical crystal disposed within a resonator-like structure, and to output the expanded pump beamlets, thereby enabling the configuration of a compact laser amplifier system.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 313,605, entitled "LASER AMPLIFIER AND METHOD OF MANUFACTURING UTILIZING MULTIPLE ENDPOINT SPOTS," filed February 24, 2022, the contents of which are incorporated by reference in their entirety herein. [Background technology]

[0002] background Currently, the state of the art in ultrafast fiber lasers is performance limited. For example, currently available ultrafast fiber lasers are limited in terms of peak and average power. For example, currently available ultrafast laser devices are typically limited to around 200 watts (200W), especially due to so-called transverse mode instability. See C. Jauregui et al, "Transverse mode instability," Adv. Opt. Photonics 12 (2), 429-484 (2020).

[0003] In response to this, various configurations have been explored to produce ultrafast laser systems with higher peak power and higher average power. For example, a system has been proposed that includes a complex and expensive chirped pulse amplification (CPA) in combination with a large area photonic crystal fiber, which could achieve pulse energies of perhaps more than 1 mJ. See F. Roeser et al, "Millijoule pulse energy high repetition rate femtosecond fiber chirped-pulse amplification system," Opt. Lett. 32, No.24 (2007). Although the proposed system has been useful to some extent, it has its own limitations and problems. For example, the inclusion of a CPA increases the complexity and cost of the system.

[0004] In contrast, the Innoslab laser amplifier as described by Russbueldt (see P. Russbueldt et al, "400 W Yb:YAG Innoslab fs-amplifier", Opt. Exp. 17, No. 15, (2009) and U.S. Patent No. 9,484,705 to P. Russbueldt et al., "Optically end-pumped slab amplifier comprising pump modules arranged in a distributed manner") addresses and solves both problems, achieving over 400 W and capable of delivering μJ output power without a CPA and mJ output power with a moderate CPA. The Innoslab design utilizes a homogenous pump field (line) across the crystal aperture, derived from multiple diode bars. The pump shaping and transfer optics used in the Innoslab system and similar slab amplifiers are difficult to design, expensive to manufacture, and bulky. In addition, signal beam shaping and alignment are complex and time consuming. Furthermore, with Innoslab systems and similar slab amplifiers, it is difficult to achieve very good beam quality (i.e. low beam propagation factor M2 with a circular, uniformly smooth Gaussian beam through the caustics).

[0005] In light of the above, Schulte and Russbueldt have produced a solution entitled "Scalable USP Power Amplifier Based on the Multirod Concept" in the Annals of Laser Technology ILT 2015 of the Fraunhofer Institute. However, the Annals does not disclose the important technical details, manufacturing considerations, and configuration of the system, and focuses on the theoretical possibility of building such a system. Furthermore, Schulte and Russbueldt's paper states that an excitation wavelength of 940 nm is preferred because it places fewer constraints on the coating design of the dichroic mirror. In addition, only half of the excitation power per spot (50 W) is reported, which produces half of the maximum power (150 W). Higher powers are useful and required in some applications.

[0006] In light of the above, there is a continuing demand for high power (>100 W) and high repetition rate laser amplifier systems. Summary of the Invention

[0007] overview The present application discloses various embodiments of a laser amplifier system that utilizes multiple end pump spots to pump an optical crystal during the amplification process. The device disclosed herein includes at least one fiber-coupled laser diode array as a pump source. The pump source outputs multiple pump beamlets that are introduced into a telecentric telescope configured to expand each individual pump beamlet such that the pump beamlets remain parallel and substantially non-diverging, and output the expanded pump beamlets. The amplifier pump signal including the multiple expanded pump beamlets is incident on an optical crystal located in a resonator-like amplifier. At least one input signal is also incident on the optical crystal and is amplified by the optical crystal by repeatedly traversing the resonator-like amplifier and repeatedly incident on the optical crystal. Finally, the amplified signal is output from the resonator-like amplifier. In one embodiment, unlike prior art amplifiers, the present system includes a single telescope that expands all the pump beamlets while keeping the individual pump beamlets substantially non-diverging. Additionally, unlike prior art systems that require multiple optical crystals, the present system can include a single optical crystal, thereby enabling the construction of a compact laser amplifier system.

[0008] In a specific embodiment, the present application is directed to a laser amplifier system, including at least one fiber-coupled laser diode array configured to output at least one pump signal at a wavelength between 850 nm and 1250 nm. At least one telecentric telescope may be in optical communication with the fiber-coupled laser diode array and configured to receive the pump signal and output at least one amplifier pump signal. At least one signal source may be configured to output at least one input signal. At least one resonator-like amplifier is in communication with the telecentric telescope and the signal source. The resonator-like amplifier may be defined by at least one signal mirror, at least one pump injection mirror, at least one pump output mirror, and at least one mirror. The resonator-like amplifier may have an optical path length of about 50 mm to about 700 mm defined by the signal mirror, the pump input mirror, and the pump output mirror, and the mirror. The location of the at least one optical crystal may be within the resonator-like amplifier and may be configured to receive at least a portion of the pump signal and output at least one amplifier output signal from the resonator-like amplifier.

[0009] In another embodiment, the present application is directed to a laser amplifier system including at least one fiber-coupled laser diode array configured to output at least one pump signal formed from a plurality of pump beamlets individually launched from the fiber-coupled laser diode array. A telecentric telescope in optical communication with the at least one fiber-coupled laser diode array may be configured to receive the individual pump beamlets forming the pump signal and output a plurality of expanded pump beamlets forming individual amplifier pump signals. At least one signal source may be configured to output at least one input signal. At least one cavity-like amplifier is in communication with the telecentric telescope and the signal source. The cavity-like amplifier is defined by at least one signal mirror, at least one pump injection mirror, at least one pump output mirror, and at least one mirror. An optical crystal may be disposed within the cavity-like amplifier and configured to be pumped by the individual plurality of amplifier pump signals and the input signal and to output at least one amplifier output signal from the cavity-like amplifier.

[0010] In yet another embodiment, the present application is directed to a laser amplifier system including at least one fiber-coupled laser diode array configured to output at least one pump signal formed from a plurality of pump beamlets individually emitted from the fiber-coupled laser diode array. A telecentric telescope may be in optical communication with the fiber-coupled laser diode array and configured to receive the individual pump beamlets forming the at least one pump signal and output the individual amplifier pump signals. At least one signal source may be configured to output at least one input signal. At least one resonator-like amplifier may be in communication with the telecentric telescope and the signal source. At least one optical crystal may be disposed within the resonator-like amplifier and configured to be pumped by the individual pump beamlets and the input signal and output at least one amplifier output signal from the resonator-like amplifier.

[0011] Other features and advantages of the laser amplifier utilizing multiple end pump spots and the method of manufacture will become apparent from a consideration of the following detailed description. [Brief description of the drawings]

[0012] BRIEF DESCRIPTION OF THE DRAWINGS The drawings disclose exemplary embodiments and are not intended to describe all embodiments of the laser amplifier system and method of manufacture utilizing multiple end pumping spots. To save space or for a more effective explanation, obvious or unnecessary details may be omitted. Conversely, an embodiment may be practiced without all of the details disclosed with respect to a specific embodiment. When the same reference number appears in different drawings, the reference number refers to the same or similar components or steps. The novel aspects of the laser amplifier system and method of manufacture utilizing multiple end pumping spots disclosed herein will become more apparent by considering the following drawings.

[0013] [Figure 1A] FIG. 1A shows a schematic diagram of an embodiment of a laser amplifier system having a cavity-like amplifier.

[0014] [Figure 1B] FIG. 1B shows a schematic diagram of another embodiment of a laser amplifier system having a cavity-like amplifier.

[0015] [Diagram 2] FIG. 2 shows a perspective view of an embodiment of a laser amplifier system having a cavity-like amplifier.

[0016] [Diagram 3] FIG. 3 shows an exploded perspective view of an embodiment of a fiber-coupled laser diode array pump source for use with an embodiment of a laser amplifier system.

[0017] [Figure 4A] FIG. 4A shows a perspective view of an embodiment of a fiber-coupled laser diode array pump source for use with an embodiment of a laser amplifier system.

[0018] [Figure 4B] FIG. 4B shows a perspective view of another embodiment of a fiber-coupled laser diode array pump source for use with embodiments of the laser amplifier system.

[0019] [Diagram 5] FIG. 5 shows a side view of an embodiment of a telescope for use with an embodiment of a laser amplifier system.

[0020] [Figure 6] FIG. 6 shows a side view of a telescope traversed by multiple excitation beamlets for use with an embodiment of a laser amplifier system.

[0021] [Figure 7] FIG. 7 shows a schematic diagram of an embodiment of a cavity-like amplifier for use with an embodiment of a laser amplifier system.

[0022] [Figure 8] FIG. 8 illustrates a perspective view of an embodiment of an optical crystal for use with an embodiment of a laser amplifier system.

[0023] [Figure 9] FIG. 9 shows a perspective view of an embodiment of an optical crystal upon which multiple pump beams are incident for use with an embodiment of a laser amplifier system.

[0024] [Figure 10] FIG. 10 shows a perspective view of another embodiment of an optical crystal for use with an embodiment of a laser amplifier system.

[0025] [Figure 11] FIG. 11 shows a perspective view of another embodiment of an optical crystal for use with an embodiment of a laser amplifier system.

[0026] [Figure 12] FIG. 12 shows a perspective view of another embodiment of an optical crystal for use with an embodiment of a laser amplifier system.

[0027] [Figure 13] FIG. 13 shows a perspective view of another embodiment of an optical crystal for use with an embodiment of a laser amplifier system.

[0028] [Figure 14] FIG. 14 shows a perspective view of another embodiment of an optical crystal for use with an embodiment of a laser amplifier system.

[0029] [Figure 15] FIG. 15 shows a perspective view of an embodiment of a pump output mirror perpendicular to the optical axis OA for use with an embodiment of a laser amplifier system.

[0030] [Figure 16] FIG. 16 shows a perspective view of an embodiment of an excitation output mirror tilted relative to the optical axis OA for use with an embodiment of a laser amplifier system.

[0031] [Figure 17] FIG. 17 illustrates a perspective view of an amplifier pump signal injected into a cavity-like amplifier for use with an embodiment of a laser amplifier system.

[0032] [Figure 18] FIG. 18 illustrates a perspective view of an amplifier output signal output from a cavity-like amplifier used with an embodiment of a laser amplifier system.

[0033] [Figure 19]FIG. 19 shows a side view of an amplifier signal traversing an optical crystal in an embodiment of a laser amplifier system.

[0034] [Figure 20] FIG. 20 shows a side view of an amplifier signal traversing an optical crystal and a microlens in an embodiment of a laser amplifier system.

[0035] [Figure 21] FIG. 21 shows a side view of an amplifier signal traversing an optical crystal and two lenses in an embodiment of a laser amplifier system.

[0036] [Figure 22] FIG. 22 shows the results of measuring the beam quality of the amplified signal using an embodiment of the laser amplifier system described herein.

[0037] [Diagram 23] FIG. 23 shows a schematic diagram of an embodiment of a laser amplifier system utilizing multiple end pump spots in a single pass configuration.

[0038] [Figure 24] FIG. 24 shows a schematic diagram of an embodiment of a laser amplifier system utilizing multiple end pump spots in a multi-pass configuration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Detailed Description This application discloses various embodiments of a laser amplifier system utilizing multiple end pump spots for the amplification of an optical signal. Exemplary embodiments are described below. Unless explicitly stated, in the drawings, the sizes, positions, etc. of components, features, elements, etc. as well as distances between them are not necessarily to scale and may be disproportionate and / or exaggerated for clarity.

[0040] The terms used herein are for the purpose of describing particular exemplary embodiments only and are not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural unless the context clearly indicates otherwise. It should be understood that the terms "comprises" and / or "comprising", as used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Unless otherwise specified, when a range of values ​​is listed, the range includes both the upper and lower limits of the range as well as any subranges therebetween. Unless otherwise indicated, terms such as "first", "second", etc. are used only to distinguish each element from one another.

[0041] Unless otherwise indicated, terms such as "about," "approximately," and the like mean that amounts, sizes, compositions, parameters, and other quantities and characteristics are not, and need not be, exact, but may be approximated and / or larger or smaller, as appropriate, to reflect tolerances, conversion factors, rounding, measurement error, and the like, as well as other factors known to those of ordinary skill in the art.

[0042] Many of the embodiments described in the following description share common components, devices, and / or elements. Components and elements that are similarly named refer consistently to the similarly named elements. For example, the embodiments described in the following detailed description generally include at least one gain medium, amplifier, and / or resonator-like amplifier disposed in at least one resonator. In addition, the embodiments described below generally include at least one telecentric telescope for coupling at least one resonator excitation signal from at least one excitation source to the resonator, amplifier, and / or resonator-like amplifier. Those skilled in the art will appreciate that any type of additional device or component may be used in the embodiments described below. Furthermore, any type of alternative telescope system may be used with the system. Thus, identical or similarly named components or features may be described with reference to other drawings even if not mentioned or described in the corresponding drawings. Also, even elements that are not labeled with reference numbers may be described with reference to other drawings.

[0043] Many different forms and embodiments are possible without departing from the spirit and teachings of this disclosure, and therefore this disclosure should not be construed as limited to the exemplary embodiments set forth herein, but rather these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will convey the gist of the disclosure to those skilled in the art.

[0044] 1A, 1B, and 2 show various embodiments of a laser amplifier using multiple end pump spots. Although the configurations of the laser amplifier systems shown in FIG. 1A, 1B, and 2 are different, these systems operate in the same manner. As shown in FIG. 1A and 2, the laser amplifier system 10 includes at least one pump source 12 configured to output one or more pump signals 14. In one embodiment, the pump source 12 includes one or more fiber-coupled laser diodes or similar emitters (hereinafter, fiber array), although one skilled in the art will appreciate that a variety of pump sources may be used with the laser amplifier system 10. Optionally, any number of pump signals 14 may be emitted from any number of pump sources 12. Additionally, multiple pump beamlets 28a-28g (see FIG. 6) may be used to form the pump signal 14.

[0045] 1 and 2, at least one telescope or optical system 16 may be configured to receive the excitation signal 14 and output at least one amplifier excitation signal 26. In the illustrated embodiment, the telescope 16 includes four lenses or optical devices, however, one skilled in the art will appreciate that any number of lenses or optical devices may be used within the telescope 16. Additionally, at least one optical device or component within the telescope 16 may be configured to be movable, removable, or repositionable. In other embodiments, the four lenses 18, 20, 22, 24 within the telescope 16 may be fixed. For example, the positions of the first lens 18, the second lens 20, the third lens 22, and the fourth lens 24 may be fixed while the source 12 is configured to be movable. In the illustrated embodiment, the first lens 18, the second lens 20, and the third lens 22 include separate elements. Optionally, one or more of the first lens 18, the second lens 20, the third lens 22, and the fourth lens 24 may be coupled to adjacent optical components to form a monolithic lens system. In one embodiment, the lenses 18, 20, 22, and 24 are fabricated from fused silica, although one skilled in the art would understand that the lenses 18, 20, 22, and 24 may be fabricated from a variety of materials. Optionally, at least one of the lenses 18, 20, 22, and 24 may be a spherical lens or any other lens configuration known in the art. Additionally, the telescope 16 may include any number of additional device alternatives, including, but not limited to, filters, spatial filters, analyzers, sensors, mirrors, gratings, and the like.

[0046] As shown in FIGS. 1A and 2, the amplifier pump signal 26 from the telescope 16 is introduced to at least one amplifier 30. In FIG. 2, at least one mirror or similar device 27 may be used to introduce the amplifier pump signal 26 to a resonator, an amplifier, and / or a resonator-like amplifier. In the illustrated embodiment shown in FIGS. 1A, 1B, and 2, the amplifier 30 comprises a ring resonator-like amplifier, but one skilled in the art will understand that any kind, type, and / or configuration of resonator-like amplifiers may be used in the laser amplifier system 10. For this reason, the amplifier 30 is referred to as a resonator-like amplifier (hereinafter, RL amplifier 30). In the illustrated embodiment, the RL amplifier 30 includes at least one pump input mirror 40 in optical communication with the telescope 16. The pump input mirror 40 may be configured to allow at least a portion of the amplifier pump signal 26 to propagate therethrough. The amplifier pump signal 26 may then be incident on one or more optical crystals or gain media 42 disposed within the RL amplifier 30. In the illustrated embodiment, the gain medium 42 is positioned on at least one optical mount or stage 44. In one embodiment, the position of the optical mount 44 within the RL amplifier 30 may be fixed. Optionally, the optical mount 44 may be movably positioned within the RL amplifier 30. In use, the amplifier pump signal 26 may be configured to deliver pump energy to the gain medium 42.

[0047] 1A, 1B, and 2, amplifier pump signal 26 traverses gain medium 42 and is incident on at least one mirror disposed within RL amplifier 30. In the illustrated embodiment, amplifier pump signal 26 traverses pump output mirror 46 to form consumed pump signal 54. Optionally, a portion of pump signal 26 may be reflected by pump output mirror 46. Consumed pump signal 54 may then be introduced to one or more beam dumps or similar devices 56.

[0048] In addition, one or more optical signals to be amplified (hereinafter, input signal 34) may be introduced into the RL amplifier 30. In the illustrated embodiment, at least one signal source 32 emits at least one input signal 34 that is introduced into the RL amplifier 30. Any type of device may be used as the signal source 32, such as, but not limited to, a mode-locked femtosecond laser source, a laser source with one or more preamplifiers, a broadband light source, a picosecond light source, a nanosecond light source, a CW light source, etc. Optionally, the signal source 32 includes an output signal of a similar laser amplifier system 10, thereby forming a multi-stage amplifier. More simply, the amplified output signal 52 of the RL amplifier 30 shown in Figures 1A, 1B, and 2 may serve as the input signal 34 of another or subsequent RL amplifier (not shown) or other amplifiers known in the art. In the illustrated embodiment, the input signal 34 is configured to be injected directly into the RL amplifier 30, thereby eliminating the need for a signal mirror 36 or 36' (see FIG. 1B) or interacting with the signal mirror 36 or 36', if present. Thus, in one embodiment, the signal mirror 36 (and / or 36') may be configured to allow at least a portion of the input signal 34 to pass through, thereby injecting the input signal 34 into the resonator-like amplifier 10. In other embodiments, the input signal 34 may be injected into the resonator-like amplifier 10 without involvement of the input mirror 36 (and / or 36'). For example, the input signal 34 may be configured to pass under, over, or to the side of the signal mirror 36 (and / or 36'). At least one of the mirrors 36, 40, 46, 48, and 36' and 48', if present, may include one or more coatings configured to be highly reflective at the wavelength of the input signal 34. Additionally, at least one of the mirrors 36, 40, 46, 48 (and 48′, if present) may include a dichroic mirror configured to be highly transmissive to the wavelength of the amplifier pump signal 26 while being highly reflective to the wavelength of the input signal 34 / amplified signal 50, thereby enabling the amplifier pump signal 26 to be extracted from the RL amplifier 30.For example, both the pump input mirror 40 and the pump output mirror 46 may be provided with one or more dichroic coatings configured to be highly transmissive at the wavelength of the amplifier pump signal 26, while being highly reflective at the wavelength of the amplified signal 50. As a result, the pump light may be simply removed from the resonator 40 after providing pump energy to the gain medium 42. In addition, at least one of the mirrors 36, 40, 46, 48, and (if present) 36' and 48' may include a flat and / or wedge-shaped body. The input signal 34 may be reflected by the pump input mirror 40 and directed to the gain medium 42. The gain medium 42 may be selected to amplify the input signal 34. To this end, the signal source 32 may be selected to provide the input signal 34 having a wavelength configured to enable amplification of the input signal 34 based on the material used to construct the gain medium 42. In one embodiment, pump output mirror 46 may be arranged to have a slight wedge, tilt, or bevel (e.g., ∼ several degrees) which may allow pump beam focusing through a nominally flat parallel plate 46 at a large angle (e.g., ∼ 45°) to vary the astigmatism of the pump signal within optical crystal 42. Any unwanted deviation of the pump beam axis propagating after pump output mirror 46 may be compensated for by adjustment of the axis of amplifier output signal 52.

[0049] 1A, 1B, and 2, the at least one amplified signal 50 output by the gain medium 42 may then be reflected by one or more additional mirrors disposed within the RL amplifier 30. For example, in the illustrated embodiment, the RL amplifier 30 includes at least one pump output mirror 46 configured to reflect substantially all of the amplified signal 50 while transmitting an amplifier pump signal 54 from the RL amplifier 30 to at least one beam dump 56. The pump output mirror 46 may include one or more dichroic coatings configured to reflect substantially all of the amplified signal 50 back to the RL amplifier 30 while transmitting essentially all of the amplifier pump signal 54. In the illustrated embodiment shown, at least one amplifier mirror 48 is disposed within the RL amplifier 30 that directs the amplified signal 50 to the input signal mirror 36, thereby forming a ring RL amplifier 30. For example, as shown in FIG. 1A, a single amplification path 31 may be created within the RL amplifier 30.

[0050] In contrast, FIG. 1B illustrates an embodiment of the RL amplifier 30 having a first amplification path 31 and at least one second amplification path 33 formed therein. In one embodiment, a single optical crystal 42 may be used to provide an amplified signal 50 to the first amplification path 31 and at least one second amplification path 33. In the embodiment illustrated in FIG. 1B, the first optical crystal 42 is configured to provide an amplified signal 50 to the first amplification path 31, while at least one second optical crystal 42' may be configured to provide at least one amplified signal 50 to the second amplification path 33. In one embodiment, the first optical crystal 42 and the second optical crystal 42' are fabricated from the same material. Optionally, the first optical crystal 42 and the second optical crystal 42' are fabricated from different materials. Furthermore, one or more additional optical elements or components 38, 38' may be disposed within the RL amplifier 30. Examples of additional components 38 include, but are not limited to, lens systems, microlens arrays, filters, spatial filters, mechanical blockers in the form of one or more holes or lines (combs), transmissive optical elements, gain media, optical crystals, polarizers, wave plates, etc. One skilled in the art will appreciate that RL amplifier 30 can be configured to have a desired optical path length L defined by the total distance between mirrors 36, 40, 46, 48. For example, with respect to Figs. 1A and 2, optical path length L can be about 50 mm to 400 mm. In other embodiments, optical path length L can be about 80 mm to 120 mm. Optionally, optical path length L can be about 100 mm to 110 mm. In contrast, optical path length L, i.e., the total distance between mirrors 36', 36, 40, 46, 48, 48' of RL amplifier 36' shown in Fig. 1B, can be about 80 mm to 700 mm. In a specific embodiment, optical path length L is about 100 mm to about 140 mm.

[0051] 3, 4A, and 4B show various views of an exemplary pump source 12 for use with the laser amplifier system shown in FIG. 1 and FIG. 2. However, one skilled in the art will appreciate that although the present application describes the use of one or more fiber-coupled diode lasers as a source of one or more pump signals 14, any number and type of laser system may be used to provide energy to the gain medium 42 located within the RL amplifier 30 (see FIG. 1 and FIG. 2). In one embodiment, the pump source 12 includes one or more fiber-coupled mid-power laser diodes. More specifically, each fiber-coupled laser diode may be configured to output at least one pump signal having a pump power between 1 W and 1500 W. In a more specific embodiment, each fiber-coupled laser diode may be configured to output at least one pump signal having a pump power of about 50 W to 200 W. Optionally, each fiber-coupled laser diode may be configured to output at least one pump signal having a pump power of about 100 W or more, although smaller laser amplifiers may be constructed with fiber-coupled laser diodes configured to output at least one pump signal having a pump power of about 10 W or more. Optionally, a very low power amplifier system may be constructed using a configuration similar to that described herein, utilizing a very low power excitation source, for example an excitation source 12 capable of outputting an excitation signal 14 on the order of 1 mW or less.

[0052] Referring again to Figures 3, 4A, and 4B, the pump source 12 may be configured to output at least one pump signal 14 at a desired wavelength. This desired wavelength will depend largely on the material used to construct the gain medium 42. In one embodiment, the pump signal 14 has a wavelength of about c, although one skilled in the art will appreciate that any type of wavelength may be used. In other embodiments, the pump signal 14 has a wavelength of about 940 nm to about 1000 nm. Optionally, the pump source 12 is configured to output at least one pump signal 14 having a wavelength of about 960 nm to about 990 nm. In one specific embodiment, the pump signal 14 has a wavelength of about 969 nm to about 971 nm. In another specific embodiment, the pump signal 14 has a wavelength of about 970 nm to about 980 nm. As shown, the pump source 12 includes a pump source body 62 defining one or more V-grooves or similar fiber alignment aids 64 formed therein or located thereon to allow accurate and secure positioning of the optical fiber body 66 of the fiber-coupled laser diode. In one embodiment, the fiber diameter is between 20 μm and 200 μm and the numerical aperture (NA) is between 0.05 and 0.22. In another embodiment, the fiber diameter is between 50 μm and 110 μm and the NA is between 0.1 and 0.22. In another specific embodiment, the fiber diameter is between 90 μm and 110 μm and the NA is between 0.1 and 0.22. Additionally, at least one cover plate 68 may be used to secure the one or more fibers within the pump source body 62. In the illustrated embodiment, seven fibers 66, each coupled to at least one laser diode, are positioned within V-grooves 64 formed in the pump device body 62, thereby forming at least one V-groove array. Those skilled in the art will appreciate that any number of fibers 66 may be used to form the excitation source 12. For example, two fibers 66 may be used. In other embodiments, ten fibers 66 are used.In use, each fiber 66 is configured to output an excitation beamlet that, when combined with excitation beamlets emitted by other fibers 66 in the excitation source 12, cooperatively forms the excitation signal 14. Thus, the excitation signal 14 includes many excitation beamlets each emitted by an individual fiber 66.

[0053] In one embodiment, the V-grooves 64 formed in the device body 62 are substantially parallel. Optionally, the V-grooves 64 formed in the device body 62 are substantially non-parallel. For example, the fibers 66 have a fiber pitch of about 5 μm or less to about 2500 μm. In other embodiments, the fibers 66 have a fiber pitch of about 250 μm to about 700 μm. In yet other embodiments, the fibers 66 have a fiber pitch of about 500 μm. One of ordinary skill in the art will appreciate that any number of fibers 66 may be disposed within the excitation device body 62. In one embodiment, at least one of the fibers 66 comprises a single mode fiber. In other embodiments, at least one of the fibers 66 comprises a multimode fiber. In other embodiments, at least one of the fibers 66 comprises a multimode fiber having a different diameter or NA than the remaining fibers. In one embodiment, at least one of the excitation device body 62 and the cover plate 68 is fabricated from glass. Optionally, at least one of the pump device body 62 and the cover plate 68 may be fabricated from a variety of materials, including, but not limited to, composite metals, alloys, ceramic materials, metals, elastomers, polymers, crystals, and crystalline materials. Alternatively, other means of fabricating a fiber array may include, but are not limited to, individually placing (e.g., adhesively bonding) the fibers in precisely drilled holes or fusing the fibers to a glass plate or similar substrate. In addition, the embodiment of the laser amplifier system 10 shown in FIG. 1 and FIG. 2 utilizes a single pump source 12. Optionally, any number of pump sources 12 may be used with the laser amplifier system shown in FIG. 1 and FIG. 2. In the illustrated embodiment, the fibers 66 are positioned vertically within the pump device body 62. Optionally, at least one of the fibers 66 may be positioned horizontally within the pump device body 62. In other embodiments, the fibers 66 may be positioned both vertically and horizontally within the pump device body 62. FIG. 4A depicts an embodiment of a pump source 12 having numerous fiber emitters aligned vertically along a common vertical axis.In contrast, FIG. 4B illustrates an embodiment of an excitation source having fiber emitters distributed vertically and horizontally within the excitation source body 62.

[0054] 5 and 6 show various views of an embodiment of a telescope or optical system 16 used with the laser amplifier system 10 shown in FIGS. 1 and 2. In one embodiment, the telescope 16 includes multiple lenses. More specifically, in one embodiment, the telescope 16 includes a first lens 18, a second lens 20, a third lens 22, and a fourth lens 24. Optionally, any number of lenses, stops, apertures, diaphragms, and / or optical devices can be used to form the telescope 16. Furthermore, any type of telescope can include a first lens 18, a second lens 20, a third lens 22, and a fourth lens 24. In one embodiment, the telescope 16 includes a telecentric telescope. Thus, in one embodiment, the first lens 18, the second lens 20, and the third lens 22 form a triplet, and the fourth lens 24 forms a lens singlet. Additionally, the lenses 18, 20, 22, 24 may be fixed and the excitation source body 62 may be movable. Optionally, at least one of the lenses used in the telescope 16 may be configured to be movable. Thus, the telescope 16 may be configured to provide a target spot size ranging from about 10 μm or less to about 2000 μm or more. In other embodiments, the telescope 16 may be configured to provide a target spot size ranging from about 200 μm to about 800 μm. Optionally, the telescope 16 may be configured to provide a target spot size ranging from about 380 μm to about 475 μm. The telescope 16 may be configured to have a desired magnification. In one embodiment, the telescope 16 has a magnification of about four times (4x). In another embodiment, the telescope 16 has a magnification of about two times (2x). Optionally, the telescope 16 has a magnification of about ten times (10x).

[0055] As shown in FIG. 6, the telescope 16 receives the pump signal 14, which includes pump beamlets emitted from each fiber-coupled laser diode used in the pump source 12, and expands the pump signal 14 to output at least one amplifier pump signal 26. As shown, the amplifier pump signal 26 includes expanded beamlets 28a-28g that form the pump signal 14. Those skilled in the art will appreciate that the number of pump beamlets that form the pump signal 14 corresponds to the number of laser diodes or other pump energy emitters used to form the pump source 12. Optionally, the multiple beamlets 28a-28g are incident on the optical crystal 42 such that substantially all facets 74 (see FIG. 8) of the optical crystal 42 are excited by the amplifier input signal 26. In other embodiments, the amplifier input signal 26 is incident on only a portion of the facets 74. Those skilled in the art will appreciate that the amplifier pump signal 26 can have any desired polarization. In one embodiment, the amplifier pump signal 26 has an s-polarized pump signal. In other embodiments, the amplifier pump signal 26 has a p-polarized light. Optionally, the amplifier pump signal 26 need not be polarized.

[0056] 7-16 show various elements used to construct the RL amplifier 30 used in the laser amplifier system 10. As shown in FIG. 7, the RL amplifier 30 includes multiple mirrors therein. In one embodiment, the RL amplifier 30 includes four mirrors 40, 46, 48, and 36. As shown, the RL amplifier 30 may form an amplifier similar to a ring resonator. Optionally, the laser system 10 may be configured to use any resonator-like amplifier configuration. The RL amplifier 30 includes at least one gain medium or optical crystal 42 therein. The gain medium 42 may be disposed within or held by at least one optical mount 44. In one embodiment, the optical mount 44 is disposed at a fixed position within the RL amplifier 30. Optionally, the optical mount 44 may be disposed within the RL amplifier 30. Thus, the optical mount 44 may be selectively movable. Additionally, the optical mount 44 may be configured to provide one or more cooling or thermal control fluids to the gain medium 44. This allows the user to thermally manage the environmental conditions within the resonator 34 or gain medium 42. Optionally, the optical mount 44 need not include a thermal management system or device.

[0057] As shown in Figures 8 and 9, the gain medium 42 includes at least one device body 72 having at least one end facet 74 and at least one elongated facet 78. As shown in Figures 8 and 9, in one embodiment, the gain medium 42 is configured to receive the amplifier pump signal 26 at the end facet 74. In another embodiment, the gain medium 42 is configured to receive the amplifier pump signal 26 at the elongated facet 74. As shown, seven pump spots 76 are formed on the end facet 74 of the gain medium 42, which correspond to the pump beamlets 28a-28g that form the amplifier pump signal 26. Any number of pump spots may be formed on the end facet 72 of the gain medium 42. As shown in Figure 9, during use, the amplified signal 50 traversing the cavity-like amplifier 30 is incident on the optical crystal 42 at a different pump spot 74 than the previous one. Further, although the pump spots are arranged vertically, one skilled in the art will appreciate that any number of pump spots of any type of orientation may be formed on the end facets 74 of the gain medium 42. Optionally, multiple gain media 42 may be arranged in the RL amplifier 30. For example, as shown in FIG. 10, four gain media 42 are arranged adjacent to each other to provide a gain medium system 43 that provides a compact, high gain amplifier system. In one embodiment, one or more thermal management devices or systems (not shown) may be arranged between each gain medium 42 to selectively control the thermal properties of the gain medium system 43. Optionally, the gain medium system 43 need not include a thermal management system. For example, FIG. 11 shows a monolithic gain medium 42 that allows vertically and horizontally distributed end spot access to increase the gain of the amplifier.

[0058] As shown in Figures 8-14, the gain medium 42 can be fabricated with any type of configuration, material, doping level, etc. For example, in one embodiment, the gain medium 42 is fabricated from a Yb:YAG material grown as a single crystal. In another embodiment, the gain medium 42 is fabricated from a Yb:YAG material as a ceramic. In other embodiments, the gain medium 42 is fabricated from Yb:Lu2O3, Yb:Sc2O3, Yb:GGG, Yb:KYW, Yb:CALGO, Yb:CaF2, Yb:CNGG, various laser ceramics, etc. In one embodiment, the gain medium 42 is fabricated from a single Yb-doped material with a constant and / or uniform doping concentration within the crystal body. In contrast, Figure 9 illustrates an embodiment of a gain medium 42 with a varying and / or non-uniform doping concentration within the crystal body. More specifically, the gain medium body 72 has a lower doping concentration at the end facet 74 compared to the opposite end facet 74'. Thus, the doping concentration within the gain device body 72 is variable along a horizontal plane. As a result, pump beamlets 28a-28g of the pump signal 26 are incident on the lower doped end facet 74 of the gain medium body 72. More simply, the pump beamlets 28a-28g pass through a higher doping concentration while traversing the gain medium body 72. In contrast, FIG. 12 illustrates an embodiment of a gain medium body having a varying doping concentration along a vertical plane. In another embodiment, FIG. 13 illustrates an embodiment of a gain medium body 72 comprised of a plurality of gain medium body segments 72a-72g having different transverse dimensions, thicknesses, lengths, heights, widths, doping concentrations, gain medium materials, and / or the like. In yet another embodiment, FIG. 14 illustrates a gain medium body 72 formed from a first gain medium body material 72' and at least one second gain medium body material 72".

[0059] As shown in FIG. 7, mirrors 36, 40, 46, 48 may be used to form the RL amplifier 30. As shown in FIG. 15, in one embodiment, at least one of the mirrors 36, 40, 46, 48 may be positioned perpendicular to the optical axis OA. In other embodiments, at least one of the mirrors 36, 40, 46, 48 may be tilted or offset from the optical axis OA, as shown in FIG. 16. In one embodiment, the input signal mirror 36 and the pump output mirror 46 are tilted at an angle α (e.g., 2 degrees or more) from the optical axis normal, which allows the input signal 34 to be incident on the optical crystal 42 at a different location than the previous spot on the optical crystal 42 as the input signal 34 continues to repeatedly traverse the resonator-like amplifier 30. One skilled in the art will appreciate that at least one of the mirrors 36, 40, 46, 48 may be tilted at any desired angle. Optionally, at least one of the mirrors 36, 40, 46, 48 may include a wedge-shaped body, which allows the input signal 34 to be incident on the optical crystal 42 at a different location than the previous spot on the optical crystal 42 as the input signal 34 continues to repeatedly traverse the resonator-like amplifier 30. As a result, the amplified signal 50 is repeatedly amplified by the gain medium 42 and is incident on a different portion of each of the mirrors 36, 40, 46, 48 as it traverses the RL amplifier 30. Optionally, one or more optional optical elements 38 may be used within the RL amplifier 30 to change the position of the amplified signal 50 within the RL amplifier 30 (see FIGS. 1 and 2). For example, in one embodiment, one or more Brewster plates or devices may be used to change the position of the amplified signal 50 each time it traverses the RL amplifier 30. Those skilled in the art will appreciate that any type of optical device or component may be used to change the position of the amplified signal 50 as it traverses the RL amplifier 30. In the illustrated embodiment, the RL amplifier is similar to an open ring resonator or a "quasi" resonator.Optionally, at least one of mirrors 36, 40, 46, 48 may include an end mirror, thereby closing a feature similar to an open ring resonator, providing a resonator with very low intracavity power but high output power.

[0060] 7, 17, and 18 illustrate embodiments of input signal mirror 36 and pump input mirror 40 onto which resonator signals 88a-88g are repeatedly incident. More specifically, FIG. 17 illustrates input signal 34 being introduced into RL amplifier 30 and amplifier signals 88a-88g being reflected by input signal mirror 36. In contrast, FIG. 18 illustrates amplifier pump signal 26 being launched into RL amplifier 30 and amplifier signals 88a-88g being directed by pump input mirror 40 to gain medium 42. Those skilled in the art will appreciate that amplifier signals 88a-88g represent amplified signal 50 passing sequentially through RL amplifier 30 and are shown only to illustrate the resonator signals 88a-88g repeatedly changing positions across RL amplifier 30. In the embodiment illustrated in FIG. 17, input signal 34 (or there are multiple input signals 34) may be introduced into RL amplifier 30 without traversing input signal mirror 36. 17, the input signal 34 may be injected into the RL amplifier 30 below the input signal mirror 36, thereby forming at least one amplifier signal 88a. Optionally, the input signal 34 may be injected into the RL amplifier 30 above the input signal mirror 36. In other embodiments, the input signal 34 may be injected into the RL amplifier 30 to the side of the input signal mirror 36. Those skilled in the art will appreciate that any of the mirrors 36, 40, 46, 48 may act as pump input mirrors and / or input signal mirrors, allowing the system to accommodate any number, type, and configuration of master oscillator output amplifier configurations.

[0061] Thereafter, as shown in FIG. 18, amplifier signal 88a, which represents input signal 34 inside RL amplifier 30, may be incident on and reflected by pump input mirror 40, which directs amplifier signal 88a to gain medium 42. As discussed above, input signal 34 may include amplified output signals of other laser amplifier systems 10 to form a multi-stage laser amplifier. Amplified resonator signal 88b exiting gain medium 42 may be directed back to input signal mirror 36 by pump output mirror 46 and amplifier mirror 40. As shown, in one embodiment, amplifier signal 88b is offset from resonator signal 88a. Each time amplifier signals 88a-88f traverse RL amplifier 30 and are amplified by gain medium 42 (as indicated by the increased thickness of amplifier signals 88a-88g in FIGS. 17 and 18), amplifier signals 88b-88g are offset from the preceding amplifier signals 88a-88g. Finally, as shown in FIG. 18, the amplifier signal 88g is configured to avoid the pump input mirror 40, such that the amplifier signal 88g may exit the RL amplifier 30 to form at least one amplified output signal 52. In the illustrated embodiment, the amplifier signals 88a-88g are configured to pass through the RL amplifier 30 seven times. Those skilled in the art will appreciate that the RL amplifier 30 may be configured to pass the amplifier signals 88a-88g through the RL amplifier 30 any number of times, thereby allowing a user to control or modify the amplification of the amplifier signals 88a-88g. As discussed above, at least one of the mirrors 36, 40, 46, 48 may be tilted to achieve a continuous shift of the resonator signals 88a-88g within the RL amplifier 30. For example, the input signal mirror 36 and the pump output mirror 46 may be tilted to cooperatively reposition and shift the resonator signals 88a-88g passing through the RL amplifier 30, respectively. In the alternative, one or more Brewster plates or similar position shifting devices may be used to vary the position of the amplifier signals 88 a - 88 g each time they traverse the RL amplifier 30 .

[0062] FIG. 7 and FIGS. 19-21 show various views of the gain medium 42 in the RL amplifier 30 that amplifies the incident signal. As shown in FIGS. 19-21, the amplifier signal 88a traverses the RL amplifier 30 and is directed to the gain medium 42 by the pump input mirror 40. The input signal 88a is amplified inside the gain medium 42, which outputs an amplifier signal 88b. The amplifier signal 88b is slightly repositioned within the RL amplifier, for example by at least one tilt mirror 36, 40, 46, 48 in the RL amplifier 30, and is directed back to the gain medium 42 by the mirrors 46, 48, 36, 40. This causes the position of the amplifier signal 88b incident on the gain medium 42 to shift relative to the position of the amplifier signal 88a incident on the gain medium 88a. The amplifier signal 88b is further amplified by the gain medium to generate an amplified signal 88c that exits the gain medium 42. This process is repeated any number of times as the amplified signal 50 (see FIG. 7) repeatedly traverses the RL amplifier 30 until it is finally emitted from the RL amplifier 30. Optionally, as shown in FIG. 20, at least one microlens array or similar optical component 38 may be used to focus, image, or otherwise modify the amplified signal 50 within the RL amplifier 30 (see FIG. 7). In other embodiments, one or more large area lenses or similar components may be disposed within the RL amplifier 30.

[0063] The amplifier signals 88a-88g may have a desired polarization. For example, in one embodiment, at least one of the amplifier signals 88a-88g is vertically polarized (s-polarized). In another embodiment, at least one of the amplifier signals 88a-88g is horizontally polarized (p-polarized). Optionally, at least one of the amplifier signals 88a-88g may be partially polarized or unpolarized. In the illustrated embodiment, the amplifier signals 88a-88g are directed above the pump input mirror 40 to form at least one amplified output signal 52. Optionally, the amplifier signals 88a-88g may be directed below or to the side of the pump input mirror 40 to form at least one amplified output signal 52. In one embodiment, the amplified output signal 52 has a wavelength of about 1020 nm to about 1040 nm, although one of ordinary skill in the art would understand that the wavelength of the amplified output signal 52 depends on the material of the gain medium. Further, in one embodiment, the amplified output signal 52 has a power of about 10 W to about 300 W or more. One skilled in the art will appreciate that the output power from the RL amplifier 30 is dependent on numerous factors, including, but not limited to, the gain medium 42 used, the pump wavelength, the pump power, thermal management of the gain medium 42, the number of passes through the gain medium 42, etc. In one specific embodiment, the amplified output signal 52 has a power of about 150 W to about 300 W. FIG. 22 shows various measurements of the amplified output signal 52. A laser amplifier system as described in FIG. 1 was constructed. Each fiber-coupled laser diode provided a pump beamlet 28a-28g (see FIG. 6) of about 100 W to form the amplifier signal 26, which was introduced into the gain medium 42. Optionally, a fiber-coupled laser diode provided pump beamlets 28a-28g (see FIG. 6) of approximately 300 W to form an amplifier signal 26 that was introduced into the gain medium 42. Those skilled in the art will appreciate that a fiber-coupled laser diode can be configured to provide pump beamlets 28a-28g (see FIG. 6) having pump powers from approximately 2 W to approximately 1500 W or more. Additionally, an input signal 34 having a power of approximately 2 W was injected into the RL amplifier 30.In one embodiment, the input signal 34 has an input power of about 100 W. Optionally, the input signal 34 may have an input power of about 70 W to about 140 W. Optionally, the input signal 34 may have an input power of about 40 W to about 300 W. In short, the input signal 34 may have any desired input power. The amplified output signal 52 is calculated based on a beam propagation factor (M. 2 X<1.1, M 2 The beam quality is excellent, as quantitatively measured by a linearity of 0.01 μm (Y<1.1) and additionally quantitatively measured by a smooth circular beam shape with minimal deviation from a perfect Gaussian beam (TEM00), and has a power of approximately 280 W. Again, one skilled in the art will appreciate that the pump power, input power, power in the spectral band, output power, and beam quality can be varied as desired.

[0064] The laser amplifier system shown in Figures 1 and 2 allows for the amplification of input signals of a few watts to high output powers (>300W) and high energies (mJ class, low nonlinearity) with excellent beam quality that is nearly diffraction limited. In one embodiment, this is achieved without the need for additional beam shaping (astigmatism correction) or spatial filtering (removal of higher order modes without loss) in the resonator 10. This eliminates the need to include additional transmissive optics, beam shaping components, and similar devices, thereby providing a compact and easily scalable design with minimal nonlinearity. Rather than relying on additional optical components in the RL amplifier 30, the laser amplifier system 10 provides a stable ring laser resonator formed with a thermal lens formed in the gain medium with sufficient energy and sufficient end pump spot size to achieve a large spot size that reduces the B-Integral to a minimum, and does not cause the spot size in the gain medium 42 to become smaller than optimal.

[0065] In one embodiment, the RL amplifier 30 has a round trip distance of about 100 mm, which forms at least one thermal lens on the spot formed on the gain medium 42. In one embodiment, the formed thermal lens has a focal length between 30 mm and 100 mm. In one specific embodiment, the formed thermal lens has a focal length of about 50 mm, which forms a stable ring cavity mode with a waist size of about 250 μm diameter outside the gain medium 42. The mode size inside the gain medium 42 is about 380 μm. Optionally, the amplifier pump signal 26 can be coupled into the RL amplifier 30 to match the ring cavity mode (i.e., a waist size diameter of about 430 μm at a position inside the gain medium 42). Optionally, the resonator input signal 34 can be coupled into the RL amplifier 30 to match the ring cavity mode (i.e., a waist size diameter of about 250 μm at a position about 50 mm in front of the gain medium 42). As a result, the laser system 10 can be configured to provide self-sustaining design with respect to both longitudinal (e.g., thermal lens power variations) and lateral (e.g., slight misalignment of one or more of the mirrors 36, 40, 46, 48) or the input beam 34. As a result, increased thermal lensing effects can be easily compensated for by adjusting the beam diameter of the input signal 34. However, one skilled in the art will appreciate that the dimensions, magnification, pump power, input signal power, resonator dimensions, material of the gain medium, etc. can be varied to provide the desired output wavelength, output power, beam quality, etc. In one embodiment, the gain medium 42 includes Yb:YAG. However, other laser materials are readily contemplated. As such, the laser amplifier system 10 is suitable for compact, cost-effective, high beam quality laser micromachining systems (fs, ps, and ns) with output powers from less than 50 W to more than 300 W.

[0066] In addition, the laser amplifier system can be configured to provide high small signal gain (greater than 50 dB, even up to 80 dB) with very high ASE and parasitic thresholds compared to prior art systems. Thus, the design can be used as a high gain MOPA amplifier (ps, ns, fs, etc.). For example, FIGS. 23 and 24 show another configuration of the RL amplifier 30. As shown in FIG. 23, the RL amplifier 30 can include at least one pump input mirror 40 and at least one pump output mirror 46. As in the previous embodiment, the pump source 12 provides at least one pump signal 14 to the RL amplifier 30. Although not shown, it should be understood that as in the previous embodiment, at least one telescope 16 can be configured to direct at least one pump signal 14 from the pump source 12 to the RL amplifier 30 by forming at least one amplifier pump signal 26 (see FIGS. 1 and 2). Additionally, at least one input signal 34 is injected into the RL amplifier 30 via at least one coupling plane or device 39. The amplifier pump signal 26 and the input signal 34 are introduced to a gain medium 42 secured to an optical mount 44. The gain medium 42 outputs at least one amplifier signal 50 that is introduced to at least one output plane or device configured to output at least one amplified output signal from the RL amplifier 30. As with the previous embodiment, the consumed amplifier pump signal is sent from the RL amplifier 30 via a pump output mirror 46 to at least one beam dump.

[0067] FIG. 23 shows an embodiment of a single pass amplification system for amplifying the input signal 34. Therefore, it is not necessary to tilt the mirrors 40, 46. In addition, the single pass configuration may tolerate a higher pump signal 14 power and / or signal 34 power. In the alternative, FIG. 24 shows another embodiment of a RL amplifier configured for double pass amplification. As shown, the amplifier pump signal 26 and the input signal 34 are introduced into the gain medium 42. In response, the gain medium 42 outputs at least one amplifier signal 50 that is reflected back to the gain medium 42 by the amplifier mirror 49. Again, the gain medium 42 amplifies the amplifier signal 50 to form at least one re-amplified signal 50'. The re-amplified signal 50' may be output from the RL amplifier 50 to form at least one amplifier output signal 52. Again, it is not necessary to tilt the mirrors 40, 46, 49. Optionally, at least one of the mirrors 40, 46, 49 may be tilted. Additionally, various embodiments shown in this application may allow the amplifier output signal 52 to be injected into other amplifiers. In other embodiments, the amplifier output signal 52 may be injected into one or more fiber optic devices or arrays, microlens arrays, lens systems, microscopes, etc.

[0068] The embodiments disclosed herein are intended to illustrate the principles of the invention. Other modifications may be used that fall within the scope of the invention. Thus, the devices disclosed in this application are not limited to those exactly as shown and described herein.

Claims

1. at least one fiber-coupled laser diode array configured to output at least one pump signal having a wavelength between 850 nm and 1250 nm; at least one telecentric telescope in optical communication with the at least one fiber-coupled laser diode array and configured to receive the at least one pump signal and output at least one amplifier pump signal; at least one signal source configured to output at least one input signal; at least one resonator-like amplifier in communication with the at least one telecentric telescope and the at least one signal source, the at least one resonator-like amplifier being defined by at least one signal mirror, at least one pump injection mirror, at least one pump output mirror, and at least one pump input mirror, the at least one resonator-like amplifier having an optical path length defined by the at least one signal mirror, the at least one pump input mirror, the at least one pump output mirror, and the at least one pump input mirror being between 50 mm and 700 mm; at least one optical crystal disposed within the at least one resonator-like amplifier and configured to receive at least a portion of the at least one pump signal and the at least one input signal and to output at least one amplifier output signal from the at least one resonator-like amplifier; A laser amplifier system comprising:

2. 10. The laser amplifier system of claim 1, wherein the fiber-coupled laser diode array includes two or more optical fiber bodies, each optical fiber body configured to output at least one pump beamlet, the at least one pump beamlet forming the at least one pump signal.

3. 10. The laser amplifier system of claim 1, wherein the at least one pump signal has a wavelength between 960 nm and 990 nm.

4. 10. The laser amplifier system of claim 1, wherein the at least one pump signal has a wavelength between 970 nm and 980 nm.

5. 10. The laser amplifier system of claim 1, wherein the at least one telecentric telescope has a target spot size in the range of 200 μm to about 800 μm.

6. 10. The laser amplifier system of claim 1, wherein the at least one telecentric telescope has a target spot size in the range of 380 μm to about 475 μm.

7. 10. The laser amplifier system of claim 1, wherein said at least one telecentric telescope has a magnification of 4x.

8. 10. The laser amplifier system of claim 1, wherein said at least one telecentric telescope has a magnification of at least 2x.

9. 10. The laser amplifier system of claim 1, wherein at least one of the at least one signal mirror, the at least one pump injection mirror, the at least one pump output mirror, and the at least one pump input mirror includes at least one dichroic coating configured to transmit the at least one pump signal and reflect the at least one input signal.

10. 2. The laser amplifier system of claim 1, wherein the optical path length is in the range of 80 mm to 120 mm.

11. 2. The laser amplifier system of claim 1, wherein the optical path length is in the range of 100 mm to 110 mm.

12. 10. The laser amplifier system of claim 1, wherein the at least one input signal repeatedly traverses the cavity-like amplifier such that the at least one input signal is repeatedly incident on different spots on a facet of the at least one optical crystal.

13. A laser amplifier system as described in claim 1, wherein the at least one signal mirror, the at least one pump injection mirror, the at least one pump output mirror, and the at least one pump input mirror are tilted with respect to the optical axis of the resonator-like amplifier, and the at least one amplifier output signal traverses within the resonator-like amplifier such that the at least one input signal traverses the resonator-like cavity along different optical paths.

14. A laser amplifier system as described in claim 1, wherein the at least one signal mirror, the at least one pump injection mirror, the at least one pump output mirror, and the at least one pump input mirror comprise wedge-shaped bodies, and the at least one amplifier output signal traverses within the resonator-like amplifier such that the at least one input signal traverses the resonator-like cavity along different optical paths.

15. The at least one amplifier pump signal includes a plurality of pump beamlets, each beamlet being imaged onto at least one fiber-coupled laser diode forming the at least one fiber-coupled laser diode array, each beamlet forming an individual pump spot on at least one facet of the at least one optical crystal.

10. The laser amplifier system of claim 1.

16. 10. The laser amplifier system of claim 1, wherein the at least one optical crystal is fabricated from Yb:YAG.

17. 10. The laser amplifier system of claim 1, wherein the at least one optical crystal is fabricated from at least one material selected from the group consisting of Yb:Lu2O3, Yb:Sc2O3, Yb:GGG, Yb:KYW, Yb:CALGO, Yb:CaF2, and Yb:CNGG.

18. 10. The laser amplifier system of claim 1, wherein said at least one optical crystal has a uniform doping concentration.

19. 10. The laser amplifier system of claim 1, wherein said at least one optical crystal has a non-uniform doping concentration.

20. 10. The laser amplifier system of claim 1, wherein the at least one signal source comprises a mode-locked femtosecond laser source.

21. 10. The laser amplifier system of claim 1, wherein the at least one signal source comprises at least one signal source selected from the group consisting of a laser source with one or more pre-amplification, a broadband light source, a picosecond light source, a nanosecond light source, a CW light source, and a cavity-like amplifier.

22. 10. The laser amplifier system of claim 1, further comprising at least one optical element disposed within the cavity-like amplifier, the at least one optical element being selected from the group consisting of a lens system, a microlens array, a filter, a spatial filter, a mechanical blocker in the form of one or more holes or lines, a transmissive optical element, a gain medium, an optical crystal, a polarizer, and a wave plate.

23. at least one fiber-coupled laser diode array configured to output at least one pump signal formed from a plurality of pump beamlets individually emitted from the at least one fiber-coupled laser diode array; a telecentric telescope in optical communication with the at least one fiber-coupled laser diode array and configured to receive individual ones of the pump beamlets forming the at least one pump signal and to output individual amplifier pump signals; at least one signal source configured to output at least one input signal; at least one cavity-like amplifier in communication with the telecentric telescope and the at least one signal source, the at least one cavity-like amplifier being defined by at least one signal mirror, at least one pump injection mirror, at least one pump output mirror, and at least one pump input mirror; an optical crystal disposed within the at least one resonator-like amplifier and configured to be excited by the respective amplifier pump signal and the at least one input signal and to output at least one amplifier output signal from the at least one resonator-like amplifier; A laser amplifier system comprising:

24. at least one fiber-coupled laser diode array configured to output at least one pump signal formed from a plurality of pump beamlets individually emitted from the at least one fiber-coupled laser diode array; a telecentric telescope in optical communication with the at least one fiber-coupled laser diode array and configured to receive individual ones of the pump beamlets forming the at least one pump signal and to output individual amplifier pump signals; at least one signal source configured to output at least one input signal; at least one resonator-like amplifier in communication with the telecentric telescope and the at least one signal source; an optical crystal disposed within the at least one cavity-like amplifier and configured to be excited by each of the excitation beamlets and the at least one input signal and to output at least one amplifier output signal from the at least one cavity-like amplifier; A laser amplifier system comprising:

Images