Multi-pass disk laser amplifier

Abstract

The application discloses a multi-pass disk laser amplifier, which comprises a near end and a far end, a pump laser beam, a seed laser beam, a first parabolic mirror, a second parabolic mirror, a laser gain medium, a first deflection optical prism group and a second deflection optical prism group, wherein the laser gain medium comprises a medium reflection surface; the pump laser beam located at the near end is aligned to the first parabolic mirror located at the far end for incidence through a first beam collimator; and the seed laser beam located at the near end is aligned to the second parabolic mirror located at the far end for incidence after passing through a second beam collimator. Compared with a conventional multi-pass disk laser amplifier, the application has a simpler structure, a shorter amplification optical path, a more compact volume and higher system stability. Furthermore, by changing the structure of the design prism of the pump light path, 12-pass, 24-pass, 36-pass, 48-pass and other multi-pass amplifications can be realized.

Description

Technical Field

[0001] This invention belongs to the field of disk lasers, specifically relating to a multi-pass disk laser amplifier. Background Technology

[0002] In recent years, the use of ultrashort laser pulses for materials processing has become a rapidly developing field. Lasers, as important processing tools, have demonstrated unique advantages in industrial processing. As a significant branch of laser processing, ultrashort pulse laser processing at the MHz and microjoule levels is widely used in flexible circuit board manufacturing, wafer dicing, cardiovascular stent manufacturing, and solar cell manufacturing. These fields have extremely high requirements for processing precision, and minimizing heat diffusion during processing is a key method to improve processing accuracy. Another branch of ultrafast laser processing is the application of millijoule-level ultrafast laser processing. For example, a very promising application is the cutting and structuring of carbon fiber reinforced plastics (CFRP). Here, high average output power leads to higher processing speeds, repetition frequencies of hundreds of kHz, and pulse energies in the mJ range, making it possible to process larger spots and perform parallel processing of multiple spots.

[0003] For the two types of lasers mentioned above (a few MHz, microjoule level and hundreds of kHz, millijoule level), the basic principle is as follows: First, an ultrashort pulse is generated using a seed source, with a repetition frequency within 100 MHz. Then, the seed light is amplified, and the repetition frequency can be adjusted by pulse selection. Common amplifier gain media types include rod-shaped gain media, slab-shaped gain media, fiber amplification, and disk-shaped gain media. Rod-shaped gain media generally have an amplification efficiency of about three times because thermal lensing and thermal depolarization effects are severe, resulting in low beam quality after amplification. Slab-shaped gain media amplification structures use top and bottom cooling, resulting in good heat dissipation and high amplification efficiency. However, the single output beam is elongated, and the beam front distortion is severe, requiring a beam shaping system to reshape the beam, which complicates the entire amplification system. Fiber amplification is suitable for high repetition frequency and low single-pulse energy amplification. Currently, rod-shaped fibers with a core diameter of 80 μm can amplify to the hundreds of microjoule level, but the overall system size is relatively large, losing the advantage of compactness. Disk-type gain media, with a thickness of only about 200µm and water-cooled on one side, has negligible thermal effects. Simultaneously, the pump light undergoes multiple reflections on the disk-type gain medium, achieving an absorption efficiency of over 80%. The pump beam is super-Gaussian, resulting in excellent beam quality after amplification. Therefore, disk-type laser amplification is currently the preferred solution for obtaining high repetition rates, high single-pulse energy, and maintaining excellent beam quality.

[0004] Currently, a common method for obtaining ultrashort pulses in the tens of MHz and tens of microjoules range using disk-type laser gain media is to directly build a disk-type ultrashort pulse oscillator without an additional amplifier, thus directly obtaining the target parameters. U. Kelly's group at ETH Zurich has successfully designed a high-power output SESAM mode-locked disk oscillator with an average output power of 210W, a single pulse energy of 19J, and a pulse width of 780fs. The overall footprint is 1.4m long and 0.8m wide. However, further increasing the power would put pressure on the internal components because the narrow pulse width and increased nonlinearity within the cavity could damage optical components. Therefore, this type of oscillator has limitations in increasing single pulse energy. The main approach for obtaining high repetition rates (hundreds of kHz) and high single pulse energy (mJ range) using disk-type laser gain media modules is to first amplify the broadened seed source nJ-level pulse using a disk-type laser regenerative amplifier. This allows single pulse energy from 1kHz to hundreds of kHz to be directly amplified to the range of greater than 100mJ to 1mJ. To achieve higher single-pulse energy and a higher repetition rate, a disk-type laser multi-pass amplification is performed after the regenerative amplifier. Currently, Trumpf GmbH and the University of Stuttgart in Germany have made significant progress in the research of disk-type laser multi-pass amplifiers. In 2020, Trumpf GmbH developed a 1kHz, 720mJ, 920fs laser system, including a seed source. The two-stage dual-disk laser multi-pass amplifier amplifies the 240mJ output from the regenerative amplifier to 800mJ, and then compresses it to obtain 720mJ. In this system, the multi-pass amplifier achieves the purpose of multiple reflections of the beam on the disk laser crystal through multiple total reflection mirrors. Its characteristic is that the more times the beam passes through, the higher the energy extraction efficiency; however, the more mirrors used, the larger the overall system size becomes, so this type of multi-pass amplifier is often not very compact. In 2020, Trumpf developed a 1.5kW, 400kHz disk laser system. Its structure consists of a two-stage, 36-pass disk amplification system that directly amplifies the seed pulse sequence. Each multi-pass amplification system is housed in a vacuum chamber, measuring 5.74m long and 2m wide, making it quite bulky. Similarly, in 2021, the same company achieved an 800kHz, 1950W, 10ps output using a disk laser multi-pass amplification scheme. Also in 2021, Professor Zhu Xiao's research group at Huazhong University of Science and Technology simulated a dual-disc laser head amplification module with a dual-parallel mirror structure. This module is compact and has high amplification efficiency, but requires two pump sources, complicating the overall system. Summary of the Invention

[0005] In view of the shortcomings of traditional disk-type laser multi-pass amplification systems, such as complex structure, large size and particularly long optical path, the purpose of this invention is to provide an improved multi-pass disk laser amplifier.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A multi-pass disk laser amplifier includes a near end and a far end, comprising: a pump laser beam, a seed laser beam, a first parabolic mirror, a second parabolic mirror, a laser gain medium, a first deflecting optical prism group and a second deflecting optical prism group, wherein the laser gain medium includes a medium reflective surface.

[0008] The pump laser beam located at the near end is collimated by the first beam collimator and then incident on the first parabolic mirror located at the far end, so that it undergoes multiple reflections between the first deflecting optical prism group, the first parabolic mirror and the medium reflecting surface, and passes through the laser gain medium multiple times to be absorbed by the laser gain medium and form a pump spot.

[0009] The seed laser beam located at the near end is collimated by the second beam collimator and then incident on the second parabolic mirror located at the far end, so that it undergoes multiple reflections between the second deflecting optical prism group, the second parabolic mirror and the medium reflecting surface, and is magnified by passing through the pump spot multiple times.

[0010] The first parabolic reflector and the second parabolic reflector are each provided with a plurality of reflective surfaces, and the reflective surfaces are all parabolic surfaces.

[0011] The first and second deflecting optical prism groups each include several prism pairs, each prism pair includes two prisms, and the two prisms have a reflecting plane that forms a 90° angle with each other.

[0012] Preferably, the laser gain medium and the medium reflecting surface are both circular, and the first parabolic mirror and the second parabolic mirror are both annular; the medium reflecting surface, the first parabolic mirror, and the second parabolic mirror are coaxial, and the focal points of all the reflecting surfaces on the first parabolic mirror and the second parabolic mirror are located on the medium reflecting surface; the laser gain medium is located between the medium reflecting surface and the first parabolic mirror and the second parabolic mirror.

[0013] Preferably, the reflecting surfaces on both the first and second parabolic mirrors have the same equivalent focal length.

[0014] Preferably, both the first deflecting optical prism group and the second deflecting optical prism group are annular structures composed of multiple prism pairs; the first deflecting optical prism group and the second deflecting optical prism group are located between the near end and the far end and are coaxial, and the reflecting planes of all the prism pairs are uniformly distributed in an annular shape facing the far end.

[0015] Preferably, the first deflecting optical prism group further includes a plane mirror for returning the incident pump laser beam along its original path.

[0016] Preferably, the second deflecting optical prism group further includes a pyramidal reflecting prism for returning the incident seed laser beam along its original path; it also includes a thin-film polarizer and a quarter-wave plate. The seed laser beam is P-polarized light. After passing through the second beam collimator and being transmitted through the thin-film polarizer, it is converted into circularly polarized light by the quarter-wave plate and then enters the second deflecting prism. The amplified seed laser beam is converted from circularly polarized light to S-polarized light after passing through the quarter-wave plate, and is then output after being flipped 90° by the thin-film polarizer.

[0017] Preferably, the reflective surface of the first parabolic mirror is coated with a first dielectric film having high reflectivity for the pump laser beam, and the reflective surface of the second parabolic mirror is coated with a second dielectric film having high reflectivity for the seed laser beam; the reflective planes of the first deflecting optical prism group are all coated with the first dielectric film; and the reflective planes of the first deflecting optical prism group are all coated with the second dielectric film.

[0018] Preferably, the thickness of the laser gain medium is 0.15 to 0.35 mm, and it includes a front surface facing the first parabolic reflector and a rear surface facing away from the first parabolic reflector; the front surface is coated with a third dielectric film that enhances the reflection of the pump laser beam and the seed laser beam; and the rear surface is coated with a fourth dielectric film that has high reflectivity for the pump laser beam and the seed laser beam to form the dielectric reflective surface.

[0019] Preferably, the laser gain medium is fixed to the heat sink by welding, gluing or bonding processes, and the other side of the heat sink is in contact with the jet coolant to cool the laser gain medium. The heat sink is made of tungsten copper, diamond, sapphire, silicon carbide or aluminum nitride ceramic.

[0020] Preferably, the spot diameter of the seed laser beam is 75% to 85% of the spot diameter of the pump laser beam.

[0021] The advantages of this invention are: compared to traditional multi-pass disk laser amplifiers, it has a simpler structure, shorter amplification optical path, more compact size, and higher system stability. Furthermore, by changing the structure of the pump optical path prism, multi-pass amplification with 12, 24, 36, and 48 passes can be achieved. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure and optical path of the first embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram showing the positional relationship between the first deflecting optical prism group, the second deflecting optical prism group, and the laser gain medium in the first embodiment.

[0024] Figure 3 This is a schematic diagram showing the positional relationship between the first deflecting optical prism group and the laser gain medium in the first embodiment;

[0025] Figure 4 This is a schematic diagram showing the positional relationship between the second deflecting optical prism group and the laser gain medium in the first embodiment;

[0026] Figure 5 This is a schematic diagram of the optical paths of the pump laser beam and the seed laser beam in the first embodiment, where the circles represent the maximum diameter of each spot.

[0027] Figure 6 This is a schematic diagram of the optical path of the pump laser beam in the first embodiment;

[0028] Figure 7 This is a schematic diagram of the optical path of the seed laser beam in the first embodiment;

[0029] Figure 8 This is a schematic diagram of the optical path of the seed laser beam in another embodiment;

[0030] Figure 9 This is a schematic diagram of the optical path of the pump laser beam and the seed laser beam in another embodiment. Detailed Implementation

[0031] The technical solution of this patent will be further described in detail below with reference to specific embodiments.

[0032] In the description of this invention, it should be noted that the terms "far", "near", "inner", "outer", "upper", "lower", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0033] like Figures 1 to 9 As shown, the present invention provides a multi-pass disk laser amplifier, which has a light input port ( Figure 1 The left side of the image is used to distinguish between the proximal and distal ends.

[0034] Its specific structure includes: a pump laser beam 11, a seed laser beam 12, a first parabolic reflector 1, a second parabolic reflector 2, a laser gain medium 6, a first deflecting optical prism group 3 and a second deflecting optical prism group 4, and the laser gain medium 6 includes a medium reflecting surface.

[0035] The pump laser beam 11 located at the near end is collimated by the first beam collimator 7 and then incident on the first parabolic mirror 1 located at the far end. It undergoes multiple reflections between the first deflecting optical prism group 3, the first parabolic mirror 1 and the medium reflecting surface, and passes through the laser gain medium 6 multiple times to be absorbed by the laser gain medium 6 and form a pump spot.

[0036] The seed laser beam 12 located at the near end is aimed at the second parabolic mirror 2 located at the far end after passing through the second beam collimator 8. It is then reflected multiple times between the second deflecting optical prism group 4, the second parabolic mirror 2 and the medium reflecting surface, and is amplified multiple times by passing through the pump spot.

[0037] The first parabolic reflector 1 and the second parabolic reflector 2 are each provided with several reflecting surfaces, and the reflecting surfaces are all parabolic.

[0038] The first deflecting optical prism group 3 and the second deflecting optical prism group 4 both include several pairs of prisms. Each prism pair includes two prisms, and the two prisms have a reflecting plane that is at a 90° angle to each other.

[0039] The above structure enables multi-path amplification of the seed laser beam 12.

[0040] In the first embodiment of the present invention, the following structure is specifically adopted:

[0041] It also includes a thin-film polarizer 9 and a quarter-wave plate 10. The seed laser beam 12 is P-polarized light. After passing through the second beam collimator 8 and being transmitted through the thin-film polarizer 9, it is converted into circularly polarized light by the quarter-wave plate 10 and then enters the second parabolic reflector 2. After being magnified, the seed laser beam 12 is converted from circularly polarized light to S-polarized light after passing through the quarter-wave plate 10, and is output after being flipped by the thin-film polarizer 9 by 90° relative to the original incident seed laser beam 12.

[0042] The first deflecting optical prism group 3 and the second deflecting optical prism group 4 each include 5 prism pairs. To better describe the optical path, their reflection planes along the optical path are sequentially labeled as: A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, and B2, B3, B4, B5, B6, B7, B8, B9, B10, B11.

[0043] First embodiment of the present invention, for example Figures 5 to 7 As shown:

[0044] The first beam collimator 7 collimates the pump laser beam 11 and directs it onto position A1 on the first parabolic mirror 1. The first parabolic mirror 1 focuses the pump laser beam 11 onto the reflective surface of the laser gain medium 6, reflecting it to position A2 of the first parabolic mirror 1, and then reflecting it again to the first deflecting optical prism group 3. The two prisms P1 and P2 of the first deflecting optical prism group 3 deflect the transmission direction of the pump beam 11 by 180° and reflect it back to position A3 of the first parabolic mirror 1.

[0045] Similarly, the paths of the reflected and deflected light of the pump laser beam 11 are as follows:

[0046] A1→Laser gain medium 6→A2→A3→Laser gain medium 6→A4→A5→Laser gain medium 6→A6→A7→Laser gain medium 6→A8→A9→Laser gain medium 6→A10→A11→Laser gain medium 6→A12→Plane mirror 5, and then return to A1 along the original optical path through the plane mirror.

[0047] The pump laser beam 11 is repeatedly incident on the laser gain medium 6 under the action of the first deflecting optical prism group 3 and the first parabolic reflector 1, and reaches the plane reflector 5 parallel to the disk-shaped laser gain medium 6. After reflection, it returns along the original optical path and is incident on the disk-shaped laser gain medium 6 again multiple times. Finally, the pump laser beam 11 is reflected 12 times by the laser gain medium 6, that is, it is absorbed 24 times through the laser gain medium 6, forming a pump spot on it.

[0048] After passing through the second beam collimator 8, the seed laser beam 12 can be transmitted through the thin-film polarizer 9, and then converted into circularly polarized light by the quarter-wave plate 10. It is then incident on position B1 of the second parabolic mirror 2, focused and reflected onto the pump spot on the reflective surface of the laser gain medium 6, and amplified. It is then reflected back to position B2 of the second parabolic mirror 2, and then reflected onto the second deflecting optical prism group 4. The second deflecting optical prism group 4 deflects the transmission direction of the seed laser beam 12 by 180° and reflects it back to position B3 of the second parabolic mirror 2.

[0049] Similarly, the paths of the reflected and deflected light of the seed laser beam 12 are as follows:

[0050] B1→Laser gain medium 6→B2→B3→Laser gain medium 6→B4→B5→Laser gain medium 6→B6→B7→Laser gain medium 6→B8→B9→Laser gain medium 6→B10→B11→Laser gain medium 6→B12→From the corner cone reflecting prisms P5 and P6, then return to B1 along the original optical path.

[0051] The seed laser beam 12, under the action of the second deflecting optical prism group 4 and the second parabolic reflector 2, is reflected 6 times on the laser gain medium 6 and reaches position B12 on the second parabolic reflector 2. It then enters between two prisms that are at a 90° angle to each other. These two prisms form a pyramidal reflecting prism P5 and P6, which flips the seed laser beam 12 by 180° and returns along the original optical path. It then enters the laser gain medium 6 multiple times again. Finally, the seed laser beam 12 is reflected 12 times by the laser gain medium 6, that is, it is amplified 24 times by passing through the laser gain medium 6.

[0052] A second embodiment of the seed laser beam 12 optical path of the present invention, for example Figure 8 As shown:

[0053] The second deflecting prism group 4 can be left without forming a pyramidal reflecting prism at position B12, instead leaving a light outlet directly so that the amplified laser can be output directly from position B12.

[0054] When there is no pyramidal reflecting prism, the thin-film polarizer 9 and the quarter-wave plate 10 can be removed, and at this time, the seed laser beam 12 will be amplified 12 times, that is, it will be reflected 6 times on the laser gain medium 6.

[0055] The paths of the reflected and deflected light of the seed laser beam 12 are as follows:

[0056] B1→Laser gain medium 6→B2→B3→Laser gain medium 6→B4→B5→Laser gain medium 6→B6→B7→Laser gain medium 6→B8→B9→Laser gain medium 6→B10→B11→Laser gain medium 6→B12, and then directly reflected to the output port.

[0057] A third embodiment of the seed laser beam 12 optical path of the present invention, for example Figure 9 As shown:

[0058] The structure of the second deflecting prism group 4 can be the same as that of the first deflecting prism group 3, and its plane mirror 14 reflects the seed laser beam 12 back to position B1 along the original path.

[0059] The paths of the reflected and deflected light of the seed laser beam 12 are as follows:

[0060] B1→Laser gain medium 6→B2→B3→Laser gain medium 6→B4→B5→Laser gain medium 6→B6→B7→Laser gain medium 6→B8→B9→Laser gain medium 6→B10→B11→Laser gain medium 6→B12→Plane mirror 14, and then after being reflected by plane mirror 14, it returns to B1 along the original optical path.

[0061] The laser gain medium 6 and the medium reflecting surface are both circular, and the first parabolic reflector 1 and the second parabolic reflector 2 are both annular; the medium reflecting surface, the first parabolic reflector 1 and the second parabolic reflector 2 are coaxial, and the focal points of all the reflecting surfaces on the first parabolic reflector 1 and the second parabolic reflector 2 are located on the medium reflecting surface; the laser gain medium 6 is located between the medium reflecting surface and the first parabolic reflector 1 and the second parabolic reflector 2.

[0062] Furthermore, the reflecting surfaces on the first parabolic mirror 1 and the second parabolic mirror 2 both have the same equivalent focal length to achieve the reflection requirement.

[0063] The first deflecting optical prism group 3 and the second deflecting optical prism group 4 are both ring structures composed of multiple prism pairs; the first deflecting optical prism group 3 and the second deflecting optical prism group 4 are located between the near end and the far end and are coaxial, and the reflection planes of all prism pairs are evenly distributed in a ring towards the far end.

[0064] The first deflecting optical prism group 3 also includes a plane mirror 5, which is used to return the incident pump laser beam 11 along its original path.

[0065] The second deflecting optical prism group also includes a pyramidal reflecting prism P5 and P6, which are used to return the incident seed laser beam 12 along the original path.

[0066] The reflective surface of the first parabolic mirror 1 is coated with a first dielectric film that has high reflectivity for the pump laser beam 11, and the reflective surface of the second parabolic mirror 2 is coated with a second dielectric film that has high reflectivity for the seed laser beam 12; the reflective planes of the first deflecting optical prism group 3 are all coated with the first dielectric film; and the reflective planes of the first deflecting optical prism group 4 are all coated with the second dielectric film.

[0067] The thickness of the laser gain medium 6 is 0.15 to 0.35 mm, and it includes a front surface facing the first parabolic reflector 1 and a rear surface facing away from the first parabolic reflector 1; the front surface is coated with a third dielectric film that enhances the reflection of the pump laser beam 11 and the seed laser beam 12; and the rear surface is coated with a fourth dielectric film that has high reflectivity for the pump laser beam 11 and the seed laser beam 12 to form a dielectric reflective surface.

[0068] The first, second, third, and fourth dielectric films used in this invention refer to optical thin films with enhanced reflectivity. These are common techniques in the field and can be metal reflective films, all-dielectric reflective films, or a combination of both (metal-dielectric reflective films). The selection of their types and the coating methods are common industry practices and are not the innovation of this invention; therefore, they are not described in detail.

[0069] The laser gain medium 6 is fixed to the heat sink by welding, gluing or bonding. The other side of the heat sink is in contact with the jet coolant to cool the laser gain medium 6. The heat sink is made of tungsten copper, diamond, sapphire, silicon carbide or aluminum nitride ceramic.

[0070] The spot diameter of the seed laser beam 12 is 75% to 85% of the spot diameter of the pump laser beam 11 to meet the mode matching condition.

[0071] The pump laser beam 11 of this invention uses an outer-ring pump laser with a wavelength of 940nm and an inner-ring output laser with a wavelength of 1030nm. The pump laser and the output laser are combined into one, eliminating the need for a resonant cavity. In contrast, most existing patents use pump lasers with wavelengths such as 940nm or 969nm, and do not include a laser with a wavelength of 1030nm.

[0072] This invention employs a double-ring structure of a first deflecting optical prism group 3 and a second deflecting optical prism group 4 to amplify the laser. Existing lasers can absorb the laser through a single-ring prism but cannot amplify it. The reference prior art application number is CN208904395U, and the invention title is "A Cylindrical Prism Total Internal Reflection Multi-Stroke Pumped Absorbing Disk Laser".

[0073] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A multi-pass disk laser amplifier, comprising a near end and a far end, characterized in that, include: The laser beam comprises a pump laser beam, a seed laser beam, a first parabolic mirror, a second parabolic mirror, a laser gain medium, a first deflecting optical prism group, and a second deflecting optical prism group, wherein the laser gain medium includes a dielectric reflective surface. The pump laser beam located at the near end is collimated by the first beam collimator and incident on the first parabolic reflector located at the far end, so that it undergoes multiple reflections between the first deflecting optical prism group, the first parabolic reflector and the medium reflecting surface, and passes through the laser gain medium multiple times to be absorbed by the laser gain medium and form a pump spot. The seed laser beam located at the near end is collimated by the second beam collimator and then incident on the second parabolic mirror located at the far end, so that it undergoes multiple reflections between the second deflecting optical prism group, the second parabolic mirror and the medium reflecting surface, and is magnified by passing through the pump spot multiple times. The first parabolic reflector and the second parabolic reflector are each provided with a plurality of reflective surfaces, and the reflective surfaces are all parabolic surfaces. The first and second deflecting optical prism groups each include several prism pairs, each prism pair includes two prisms, and both prisms have a reflecting plane that is at a 90° angle to each other.

2. The multi-pass disk laser amplifier according to claim 1, characterized in that: The laser gain medium and the medium reflecting surface are both circular, and the first parabolic mirror and the second parabolic mirror are both annular; the medium reflecting surface, the first parabolic mirror and the second parabolic mirror are coaxial, and the focal points of all the reflecting surfaces on the first parabolic mirror and the second parabolic mirror are located on the medium reflecting surface; the laser gain medium is located between the medium reflecting surface and the first parabolic mirror and the second parabolic mirror.

3. The multi-pass disk laser amplifier according to claim 2, characterized in that: Furthermore, the reflecting surfaces on both the first and second parabolic mirrors have the same equivalent focal length.

4. The multi-pass disk laser amplifier according to any one of claims 2 or 3, characterized in that: Both the first and second deflecting optical prism groups are annular structures composed of multiple prism pairs; the first and second deflecting optical prism groups are located between the near end and the far end and are coaxial, and the reflecting planes of all the prism pairs are uniformly distributed in a ring towards the far end.

5. The multi-pass disk laser amplifier according to claim 4, characterized in that: The first deflecting optical prism group also includes a plane mirror for returning the incident pump laser beam along its original path.

6. The multi-pass disk laser amplifier according to claim 4, characterized in that: The second deflecting optical prism group also includes a pyramidal reflecting prism for returning the incident seed laser beam along its original path; it also includes a thin-film polarizer and a quarter-wave plate. The seed laser beam is P-polarized light. After passing through the second beam collimator and being transmitted through the thin-film polarizer, it is converted into circularly polarized light by the quarter-wave plate and then enters the second deflecting prism. The amplified seed laser beam is converted from circularly polarized light to S-polarized light after passing through the quarter-wave plate, and is then output after being flipped 90° by the thin-film polarizer.

7. The multi-pass disk laser amplifier according to claim 6, characterized in that: The first parabolic reflector has a reflective surface coated with a first dielectric film that has high reflectivity for the pump laser beam, and the second parabolic reflector has a reflective surface coated with a second dielectric film that has high reflectivity for the seed laser beam; the reflective planes of the first deflecting optical prism group are all coated with the first dielectric film; and the reflective planes of the first deflecting optical prism group are all coated with the second dielectric film.

8. The multi-pass disk laser amplifier according to claim 7, characterized in that: The thickness of the laser gain medium is 0.15 to 0.35 mm, and it includes a front surface facing the first parabolic reflector and a rear surface facing away from the first parabolic reflector; the front surface is coated with a third dielectric film that enhances the reflection of the pump laser beam and the seed laser beam; and the rear surface is coated with a fourth dielectric film that has high reflectivity for the pump laser beam and the seed laser beam to form the dielectric reflective surface.

9. The multi-pass disk laser amplifier according to claim 8, characterized in that: The laser gain medium is fixed to the heat sink by welding, gluing or bonding processes. The other side of the heat sink is in contact with the jet coolant to cool the laser gain medium. The heat sink is made of tungsten copper, diamond, sapphire, silicon carbide or aluminum nitride ceramic.

10. The multi-pass disk laser amplifier according to claim 1, characterized in that: The spot diameter of the seed laser beam is 75% to 85% of the spot diameter of the pump laser beam.

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