A high-efficiency laser multi-pass amplification device

Abstract

The present invention provides a high-efficiency laser multi-pass amplifier. The device comprises two pump source units, a gain medium, and a seed light reflector group. Each pump source unit comprises a pump source and a pump light reflector. The seed light reflector group comprises a first seed light reflector, a second seed light reflector, and a third seed light reflector. The gain medium is cylindrical, with a first film layer disposed on the upper bottom surface, a second film layer disposed on the lower bottom surface, and threads disposed on the side surfaces. The pump source unit is located on the upper bottom surface of the gain medium, and the reflective surface of the pump light reflector faces the upper bottom surface of the gain medium. The seed light reflector group is located on the lower bottom surface of the gain medium. The first film layer reflects the seed light and transmits the pump light, while the second film layer transmits the seed light and reflects the pump light. By increasing the number of times the pump light penetrates the gain medium, the present invention significantly reduces transverse parasitic oscillations while maintaining the amplifier's output efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrashort pulse laser amplifiers, and in particular to a high-efficiency laser multi-pass amplifier device. Background Art

[0002] Currently, femtosecond laser systems based on chirped pulse amplification (CPA) technology can achieve peak powers of 10 PW. While pursuing high peak powers, the terminal amplifier must utilize a large-aperture gain medium, whose lateral gain is much greater than the longitudinal gain. When the pump laser energy density is high enough, transverse parasitic oscillations will occur within the gain medium, consuming the energy stored there. Furthermore, when the gain medium absorbs the pump light, some of the energy is stored within the gain medium, causing it to heat up. At thermal equilibrium, the temperature gradient within the gain medium transforms it into a lens-like medium, a phenomenon known as thermal lensing. This thermal lensing effect not only distorts the wavefront of the amplified laser seed beam but also causes the beam to focus. This leads to a spatial mode mismatch between the laser seed source and the pump light, reducing energy extraction efficiency. Therefore, overcoming these challenges will be key to further improving laser peak power.

[0003] To suppress transverse parasitic oscillations, Chinese patent CN104253373A discloses a Ti:sapphire laser amplifier. This approach aims to suppress parasitic oscillations by controlling the polarization of the pump light. Specifically, when the pump light is polarized parallel to the Ti:sapphire crystal axis (π polarization), the absorption cross-sectional area of ​​the Ti:sapphire crystal is maximized; when the pump light is polarized perpendicular to the Ti:sapphire crystal axis (σ polarization), the absorption cross-sectional area of ​​the Ti:sapphire crystal is minimized. Therefore, by changing the pump light polarization, the transverse gain of the Ti:sapphire crystal can be reduced. While the Ti:sapphire laser amplifier disclosed in this patent can reduce the transverse gain of the gain medium, the absorption rate of the pump light decreases when the gain medium length is fixed, reducing amplifier efficiency. Another common method for suppressing transverse parasitic oscillations is to use a refractive index matching fluid on the crystal surface to increase the loss of transverse parasitic oscillations. However, this method is difficult to achieve perfect refractive index matching because the refractive index of the matching fluid varies with polarization and wavelength, resulting in limited effectiveness. Alternatively, the lateral gain can be effectively reduced by increasing the thickness of the gain medium to reduce the doping concentration and the pump light absorption coefficient; however, this measure requires the use of a thick gain medium, which increases the cost and material dispersion, making subsequent pulse compression more difficult. Summary of the Invention

[0004] Aiming at the problem that the suppression effect of existing laser amplifiers is limited and affects the output efficiency of the amplifier in the process of suppressing transverse parasitic oscillation and thermal lens effect, the present invention provides a high-efficiency laser multi-pass amplification device.

[0005] In a first aspect, the present invention provides a high-efficiency laser multi-pass amplification device, comprising: two pump source units, a gain medium, and a seed light reflector group; each of the pump source units comprises: a pump source and a pump light reflector; the seed light reflector group comprises: a first seed light reflector, a second seed light reflector, and a third seed light reflector;

[0006] The gain medium is cylindrical, with a first film layer provided on the upper bottom surface, a second film layer provided on the lower bottom surface, and a thread provided on the side surface. The pump source unit is located on the upper bottom surface side of the gain medium. The pump light reflector is located between the pump source and the gain medium and on the reflected light path after the pump light generated by the pump source is reflected by the gain medium, and the reflective surface of the pump light reflector faces the upper bottom surface of the gain medium; the seed light reflector group is located on the lower bottom surface side of the gain medium; the first film layer reflects the seed light and transmits the pump light, and the second film layer transmits the seed light and reflects the pump light.

[0007] Furthermore, the pump light generated by the pump source in one of the pump source units avoids the pump light reflector in the other pump source unit, enters the gain medium, is reflected by the lower bottom surface of the gain medium and penetrates the gain medium again, and then is reflected by the pump light reflector in the one of the pump source units and returns along the original path to penetrate the gain medium;

[0008] The seed laser is reflected by the first seed light reflector into the gain medium, reflected by the upper bottom surface of the gain medium and penetrates the lower bottom surface of the gain medium, and then reflected by the second seed light reflector and the third seed light reflector in sequence into the gain medium, reflected by the upper bottom surface of the gain medium into and penetrates the lower bottom surface of the gain medium to complete amplification.

[0009] Furthermore, the mirror center angle between the first seed light reflector and the second seed light reflector is greater than zero; and the mirror center angle between the first seed light reflector and the third seed light reflector is greater than zero.

[0010] Furthermore, the reflective surface of each pump light reflector is coated with a high reflective film for zero-degree incidence of pump light; and the reflective surface of each seed light reflector in the seed light reflector group is coated with a high reflective film for 45-degree incidence of seed light.

[0011] Furthermore, a cooling device is provided on the side of the gain medium.

[0012] In a second aspect, the present invention further provides a high-efficiency laser multi-pass amplification device, comprising: a first pump source, a gain medium, a dichroic mirror, and a seed light reflector group, wherein the seed light reflector group comprises: a first seed light reflector, a second seed light reflector, and a third seed light reflector;

[0013] The gain medium is cylindrical, and a thread is provided on the side of the gain medium; the dichroic mirror is located on the upper bottom surface of the gain medium, the seed light reflector group and the first pump source are located on the lower bottom surface of the gain medium, the reflective surface of the seed light reflector group faces the lower bottom surface of the gain medium, and the non-reflective surface of the seed light reflector group faces the first pump source;

[0014] The pump light generated by the first pump source is incident on the gain medium through the gaps between the various sub-light reflectors in the seed light reflector group; the seed laser is reflected by the first seed light reflector and enters and penetrates the gain medium, is reflected by the dichroic mirror and enters and penetrates the gain medium again, and then is reflected by the second seed light reflector and the third seed light reflector in sequence and enters and penetrates the gain medium, and is amplified after being reflected by the dichroic mirror and entering and penetrating the gain medium.

[0015] Furthermore, the upper bottom surface and the lower bottom surface of the gain medium are both coated with anti-reflection films that enhance the transmission of the seed laser and the pump light; and a cooling device is also provided on the side surface of the gain medium.

[0016] Furthermore, the mirror center angle between the first seed light reflector and the second seed light reflector is greater than zero; and the mirror center angle between the first seed light reflector and the third seed light reflector is greater than zero.

[0017] Furthermore, the dichroic mirror is coated with a zero-degree incident anti-reflection film for pump light and a 5-degree incident high-reflection film for seed light; the reflective surface of each seed light reflector in the seed light reflector group is coated with a 45-degree incident high-reflection film for seed light.

[0018] Furthermore, a second pump source is included, and the second pump source is located on the upper bottom surface side of the gain medium, and the dichroic mirror is located between the second pump source and the gain medium.

[0019] Beneficial effects of the present invention:

[0020] (1) The present invention sets two pump light reflectors on one side of the gain medium, and plates seed light reflection, pump light transmission film and seed light transmission, pump light reflection film on the two bottom surfaces of the gain medium, so that the pump light can pass through the gain medium multiple times, and the total absorption rate is I ( L ) (The absorption rate of the gain medium for laser is known I (L )satisfy: I ( L )=I0* e -αL .in, α is the absorption coefficient, L Under the condition that (is the length through the gain medium) is fixed, L Increasing it several times can significantly reduce the pump light absorption coefficient α , and also reduces the lateral gain. Therefore, without increasing the thickness of the gain medium, the present invention increases the number of times the pump light penetrates the gain medium, which is equivalent to increasing the length L Thus, the present invention significantly reduces transverse parasitic oscillations while maintaining amplifier output efficiency. Furthermore, because the seed light reflective film is plated on the upper bottom surface, the entire amplifier cavity length of the present invention is shortened by half compared to traditional multi-pass amplifiers, significantly reducing the device volume and significantly reducing the impact of thermal lensing on the amplifier. The overall structure is more compact, thereby improving stability.

[0021] (2) The present invention arranges a dichroic mirror and a seed light reflector on both sides of the gain medium. The seed laser passes through the second seed light reflector, the third seed light reflector, and the dichroic mirror to form an inverted V shape. Compared with the cavity length of the traditional amplifier (with seed light reflectors on both sides of the gain medium), the cavity length of the amplifier of the present invention can be shortened by half, which can greatly reduce the influence of the thermal lens effect on the amplifier. The overall structure is more compact, thereby improving the stability.

[0022] (3) By setting threads on the side of the gain medium, due to the inclination angle of the threads, the spontaneously radiated light cannot be reflected back and forth on the side of the gain medium, which can effectively reduce lateral parasitic oscillations.

[0023] (4) The present invention does not need to increase the thickness of the gain medium, so it will not increase the material dispersion, which is beneficial to subsequent pulse compression. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a high-efficiency laser multi-pass amplification device provided by an embodiment of the present invention;

[0025] Figure 2 This is a second structural schematic diagram of a high-efficiency laser multi-pass amplification device provided by an embodiment of the present invention.

[0026] Figure numerals: 1 is a seed laser source, 2 is a first seed light reflector, 3 is a second seed light reflector, 4 is a third seed light reflector, 5 is a first pump source, 6 is a second pump source, 7 is a gain medium, 8 is a cooling device, 9 is a dichroic mirror, 10 is a first pump light reflector, 11 is a second pump light reflector, S1 is an upper bottom surface, and S2 is a lower bottom surface. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, the present invention also provides a high-efficiency laser multi-pass amplification device, comprising: two pump source units, a gain medium 7, a cooling device 8, and a seed light reflector group; the two pump source units in the embodiment of the present invention are respectively: a first pump source unit and a second pump source unit. The first pump source unit includes: a first pump source 5 and a first pump light reflector 10; the second pump source unit includes: a second pump source 6 and a second pump light reflector 11; the seed light reflector group includes: a first seed light reflector 2, a second seed light reflector 3, and a third seed light reflector 4;

[0029] The gain medium 7 is cylindrical, the upper bottom surface S1 of the gain medium 7 is provided with a first film layer, the lower bottom surface S2 is provided with a second film layer, and the side surface is provided with a thread, the side surface of the gain medium 7 is provided with the cooling device 8, the pump source unit is located on the upper bottom surface S1 side of the gain medium 7, wherein the pump light reflector is located between the pump source and the gain medium 7 and on the reflected light path after the pump light generated by the pump source is reflected by the gain medium, and the reflecting surface of the pump light reflector faces the upper bottom surface of the gain medium 7. In the embodiment of the present invention, the first pump light The reflecting surfaces of the reflector 10 and the second pump light reflector 11 are both facing the upper bottom surface S1 of the gain medium 7; the first pump light reflector 10 is located on the reflected light path of the pump light generated by the first pump source 5 after being reflected by the gain medium 7; the second pump light reflector 11 is located on the reflected light path of the pump light generated by the second pump source 6 after being reflected by the gain medium 7; the seed light reflector group is located on the lower bottom surface S2 side of the gain medium 7; the first film layer reflects the seed light and transmits the pump light, and the second film layer transmits the seed light and reflects the pump light.

[0030] The side of the gain medium 7 is provided with threads. Due to the inclined angle of the threads, spontaneously emitted light cannot be reflected back and forth on the side of the gain medium 7, effectively reducing lateral parasitic oscillations and increasing the heat dissipation area of ​​the gain medium 7. To reduce thermal lensing and thermally induced birefringence effects, this embodiment of the present invention also installs a cooling device 8 on the side of the gain medium 7, which surrounds the side of the gain medium 7. The cooling medium used in the cooling device 8 can be a liquid such as water or a mixed liquid, or compressed helium or other gas that can generate low temperatures.

[0031] The pump light generated by the pump source in one of the pump source units avoids the pump light reflector in the other pump source unit and enters the gain medium 7, is reflected by the lower bottom surface S2 of the gain medium 7 and penetrates the gain medium 7 again, and then is reflected by the pump light reflector in one of the pump source units and returns along the original path to penetrate the gain medium 7. Taking the optical path of the first pump source 5 as an example, the pump light generated by the first pump source 5 avoids the second pump light reflector 11 (for example, passes above or to the side of the second pump light reflector 11, i.e., does not penetrate the second pump light reflector 11), transmits through the upper bottom surface S1 of the gain medium 7, enters the gain medium 7, is reflected by the lower bottom surface S2 of the gain medium 7, and again penetrates the upper bottom surface S1 of the gain medium 7. At this point, the pump light has passed through the gain medium 7 twice. Then, the pump light, which has again penetrated the upper bottom surface S1 of the gain medium 7, strikes the first pump light reflector 10, is reflected by the first pump light reflector 10, returns along the original path, and finally avoids the second pump light reflector 11 (for example, passes above or to the side of the second pump light reflector 11). In this way, the pump light has penetrated the gain medium 7 four times between the first pump light reflector 10 and the second pump light reflector 11. At this point, due to the multiple passes through the gain medium, the energy of the pump light has been substantially absorbed by the gain medium. Similarly, the optical path of the second pump source 6 is not described again here.

[0032] The absorption rate of the gain medium for laser is known I ( L )satisfy: I ( L )=I0* e -αL .in, α is the absorption coefficient, L is the length of the gain medium. Since the pump light can pass through the gain medium multiple times, the total absorption rate I ( L ) under fixed conditions, L Increasing it several times can significantly reduce the pump light absorption coefficient α, and also reduces the lateral gain. Therefore, without increasing the thickness of the gain medium, the present invention increases the number of times the pump light penetrates the gain medium, which is equivalent to increasing the length L Thus, the present invention significantly reduces transverse parasitic oscillations while maintaining amplifier output efficiency. Furthermore, since the present invention does not require increasing the thickness of the gain medium, it does not increase material dispersion, facilitating subsequent pulse compression. Furthermore, the seed light reflective film coated on the upper bottom surface shortens the entire amplifier cavity length by half compared to conventional multi-pass amplifiers, significantly reducing the impact of thermal lensing on the amplifier, resulting in a more compact overall structure and improved stability.

[0033] The seed laser generated by the seed laser source 1 is reflected by the first seed light reflector 2, passes through the lower bottom surface S2 of the gain medium 7, enters the gain medium 7, is reflected by the upper bottom surface S1 of the gain medium 7 and penetrates the lower bottom surface S2 of the gain medium 7, and then is reflected by the second seed light reflector 3 and the third seed light reflector 4 in turn into the gain medium 7, and is reflected by the upper bottom surface S1 of the gain medium 7 into and penetrates the lower bottom surface S2 of the gain medium to complete amplification.

[0034] In this embodiment of the present invention, the seed laser source 1 is configured as a titanium sapphire preamplifier, outputting seed laser pulses with a central wavelength of 800 nm, a bandwidth of approximately 60 nm, an energy of 5 J, and a pulse repetition rate of 0.1 to 10 Hz. The two pump sources are configured to output pulses with a central wavelength of 532 nm, an energy of 50 J, and a pulse repetition rate of 0.1 to 10 Hz. The gain medium 7 is a titanium sapphire crystal, which exhibits excellent optical, thermal, and mechanical properties, making it an exceptionally high-performance laser crystal. The diameter of the two bottom surfaces of the gain medium 7 is 80 mm, and the cylindrical length is 20 mm. The first seed light reflector 2, the second seed light reflector 3, and the third seed light reflector 4 are all plane mirrors measuring Φ110 mm × 10 mm. The reflective surface of each seed light reflector in the seed light reflector group is coated with a high-reflectivity coating for seed light at 45-degree incidence. In the embodiment of the present invention, the reflective surfaces of all three seed light reflectors are coated with a high-reflectivity coating for 750-850 nm at 45-degree incidence. The included angle β1 between the first seed light reflector 2 and the second seed light reflector 3 is 5-20 degrees; and the included angle β2 between the first seed light reflector 2 and the third seed light reflector 4 is 5-10 degrees. Two pump sources are placed on the same side of the gain medium 7. Through transmission and reflection from the first and second film layers disposed on the two bottom surfaces of the gain medium 7, the pump light is reflected back and forth multiple times in the gain medium 7. The first and second pump light reflectors 10 and 11 each measure Φ80 mm x 10 mm. Their reflective surfaces are coated with a 532 nm zero-degree incident high-reflection coating. The smaller the angle between the center of the first and second pump light reflectors 10 and 11, the better the performance. The first coating on the upper bottom surface S1 of the gain medium 7 is a 750 nm to 850 nm reflective, 532 nm anti-reflection coating. The second coating on the lower bottom surface S2 of the gain medium 7 is a 750 nm to 850 nm anti-reflection, 532 nm reflective coating. This ensures high transmission and reflection of the seed light and pump light at both end faces of the gain medium 7. Because the pump light can pass through the gain medium 7 multiple times, effectively increasing the length of the gain medium 7, the titanium ion doping concentration of the gain medium 7 in this embodiment can be as low as 0.01 wt%. All of the above lens substrates are made of fused silica glass.

[0035] like Figure 2 As shown, an embodiment of the present invention further provides a high-efficiency laser multi-pass amplification device, which includes: a first pump source 5, a second pump source 6, a gain medium 7, a cooling device 8, a dichroic mirror 9 and a seed light reflector group, wherein the seed light reflector group includes: a first seed light reflector 2, a second seed light reflector 3 and a third seed light reflector 4;

[0036] The gain medium 7 is cylindrical, and the side of the gain medium 7 is provided with a thread; the cooling device 8 is provided on the side of the gain medium 7, the second pump source 6 and the dichroic mirror 9 are located on the upper bottom surface S1 side of the gain medium 7, and the dichroic mirror 9 is located between the second pump source 6 and the gain medium 7; the seed light reflector group and the first pump source 5 are located on the lower bottom surface S2 side of the gain medium 7, the reflective surface of the seed light reflector group faces the lower bottom surface S2 of the gain medium 7, and the non-reflective surface of the seed light reflector group faces the first pump source 5; the centers of the first pump source 5, the second pump source 6 and the dichroic mirror 9 are located at the same horizontal position.

[0037] The pump light generated by the first pump source 5 passes through the gaps between the various sub-light reflectors in the seed light reflector group and is incident on the gain medium 7. The pump light generated by the second pump source 6 passes through the dichroic mirror 9 and is incident on the gain medium 7. The seed laser light generated by the seed laser source 1 is reflected by the first seed light reflector 2, enters and penetrates the gain medium 7, reflects again by the dichroic mirror 9, enters and penetrates the gain medium 7, then reflects sequentially by the second seed light reflector 3 and the third seed light reflector 4, enters and penetrates the gain medium 7, and finally reflects by the dichroic mirror 9, enters and penetrates the gain medium 7, completing amplification. As can be seen from the optical path of the seed laser light described above, the seed laser light passes through the gain medium 7 four times, completing amplification, and then exits the high-efficiency laser multi-pass amplifier device. In this embodiment, the seed laser light forms an inverted V-shape after passing through the second seed light reflector 3, the third seed light reflector 4, and the dichroic mirror 9. Compared to the cavity length of a conventional amplifier (which has seed light reflectors on both sides of the gain medium), the cavity length of the amplifier of the present invention can be shortened by half.

[0038] The included angle β1 between the first seed light reflector 2 and the second seed light reflector 3 is 5-20 degrees; the included angle β2 between the first seed light reflector 2 and the third seed light reflector 4 is 5-10 degrees.

[0039] In order to achieve high transmittance of seed light and pump light at the two bottom surfaces of the gain medium 7, the upper and lower bottom surfaces of the gain medium 7 are coated with anti-reflection films that enhance the transmission of the seed laser and the pump light, and the two bottom surfaces can be optically polished before coating the anti-reflection films.

[0040] This embodiment of the present invention differs from the aforementioned embodiment in that two pump sources are positioned on either side of the gain medium 7. The titanium ion doping concentration in the gain medium 7 is 0.04 wt%. Both the upper and lower surfaces are coated with 750 nm to 850 nm and 532 nm antireflection coatings. The dichroic mirror 9 measures Φ80 mm by 10 mm and is coated with a zero-degree incident antireflection coating for pump light and a 5-degree incident high-reflection coating for seed light. In this embodiment, the dichroic mirror 9 is coated with a 532 nm zero-degree incident antireflection coating and a 750-850 nm 5-degree incident high-reflection coating. The remaining parameters are the same as those in the aforementioned embodiment and are not further described here.

[0041] The side of the gain medium 7 is provided with threads. Due to the inclined angle of the threads, spontaneously emitted light cannot be reflected back and forth on the side of the gain medium 7, effectively reducing lateral parasitic oscillations and increasing the heat dissipation area of ​​the gain medium 7. To reduce thermal lensing and thermally induced birefringence effects, this embodiment of the present invention also installs a cooling device 8 on the side of the gain medium 7, which surrounds the side of the gain medium 7. The cooling medium used in the cooling device 8 can be a liquid such as water or a mixed liquid, or compressed helium or other gas that can generate low temperatures.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A high-efficiency laser multi-pass amplification device, characterized in that: include: a first pump source unit, a second pump source unit, a gain medium, and a seed light reflector group; The first pump source unit includes a first pump source and a first pump light reflecting mirror; The second pump source unit includes a second pump source and a second pump light reflector; the seed light reflector group includes a first seed light reflector, a second seed light reflector and a third seed light reflector; the reflective surface of each pump light reflector is coated with a zero-degree incident high-reflection film for pump light; The gain medium is cylindrical, with a first film layer provided on the upper bottom surface, a second film layer provided on the lower bottom surface, and a thread provided on the side surface. A cooling device is also provided on the side surface of the gain medium. The pump source unit is located on the upper bottom surface side of the gain medium. The first pump light reflector is located between the second pump source and the gain medium and on the reflected light path after the pump light generated by the first pump source is reflected by the gain medium. The second pump light reflector is located between the first pump source and the gain medium and on the reflected light path after the pump light generated by the second pump source is reflected by the gain medium. The smaller the angle between the mirror centers of the two pump light reflectors, the better the effect. The seed light reflector group is located on the lower bottom surface side of the gain medium. The first film layer reflects the seed light and transmits the pump light, and the second film layer transmits the seed light and reflects the pump light. The pump light generated by the first pump source avoids the second pump light reflector and enters the gain medium, is reflected by the lower bottom surface of the gain medium and penetrates the gain medium again, and then is reflected by the first pump light reflector and returns along the original path to penetrate the gain medium; The pump light generated by the second pump source avoids the first pump light reflector and enters the gain medium, is reflected by the lower bottom surface of the gain medium and penetrates the gain medium again, and then is reflected by the second pump light reflector and returns along the original path to penetrate the gain medium; The seed laser is reflected by the first seed light reflector into the gain medium, reflected by the upper bottom surface of the gain medium and penetrates the lower bottom surface of the gain medium, then sequentially reflected by the second seed light reflector and the third seed light reflector into the gain medium, reflected by the upper bottom surface of the gain medium into and penetrates the lower bottom surface of the gain medium to complete amplification; The included angle between the mirror centers of the first seed light reflector and the second seed light reflector is greater than zero; the included angle between the mirror centers of the first seed light reflector and the third seed light reflector is greater than zero; The reflective surface of each seed light reflector in the seed light reflector group is coated with a high reflective film for seed light incident at 45 degrees.

2. A high-efficiency laser multi-pass amplification device, characterized in that: include: A first pump source, a second pump source, a gain medium, a dichroic mirror and a seed light reflector group, wherein the seed light reflector group includes: a first seed light reflector, a second seed light reflector and a third seed light reflector; The gain medium is cylindrical, and the side surface of the gain medium is provided with a thread; the upper bottom surface and the lower bottom surface of the gain medium are both coated with an anti-reflection film that enhances the transmission of the seed light and the pump light of the pump source; the side surface of the gain medium is also provided with a cooling device; the seed light reflector group and the first pump source are located on the lower bottom surface side of the gain medium, the second pump source is located on the upper bottom surface side of the gain medium, and the dichroic mirror is located between the second pump source and the gain medium; the reflective surface of the seed light reflector group faces the lower bottom surface of the gain medium, and the non-reflective surface of the seed light reflector group faces the first pump source; the centers of the first pump source, the second pump source and the dichroic mirror are located at the same horizontal position; the dichroic mirror is coated with a zero-degree incident anti-reflection film for pump light and a 5-degree incident high-reflection film for seed light; The pump light generated by the first pump source is incident on the gain medium through the gaps between the various sub-light reflectors in the seed light reflector group; the pump light generated by the second pump source penetrates the dichroic mirror and is incident on the gain medium; the seed laser is reflected by the first seed light reflector and enters and penetrates the gain medium, is reflected by the dichroic mirror and enters and penetrates the gain medium again, and then is reflected by the second seed light reflector and the third seed light reflector in sequence and enters and penetrates the gain medium, and is amplified after being reflected by the dichroic mirror and entering and penetrating the gain medium; wherein the seed laser forms an inverted V shape after passing through the second seed light reflector, the third seed light reflector, and the dichroic mirror; The included angle between the mirror centers of the first seed light reflector and the second seed light reflector is greater than zero; the included angle between the mirror centers of the first seed light reflector and the third seed light reflector is greater than zero; The reflective surface of each seed light reflector in the seed light reflector group is coated with a high reflective film for seed light incident at 45 degrees.

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