阅读说明：本技术 一种亚纳秒绿光激光器 (Subnanosecond green laser ) 是由 李高龙 马英俊 杨阳 李悦萌 李永辉 于 2021-08-04 设计创作，主要内容包括：本发明提供了一种亚纳秒绿光激光器,包括：发射种子光的亚纳秒种子源、对所述种子光进行多级放大的多级放大结构和对放大后的所述种子光进行倍频转换的倍频转换结构；所述多级放大结构包括第一级放大光路、第二级放大光路和第三级放大光路；所述第一级放大光路包括依次设置的第一种子光路、第一激光晶体、0°反射镜和第一泵浦模块；所述第二级放大光路包括依次设置的第二种子光路、第二激光晶体、0°反射镜和第二泵浦模块；所述第三级放大光路包括依次设置的第三种子光路、第三激光晶体、泵浦分光镜和第三泵浦模块。本发明提供的亚纳秒绿光激光器,输出的绿光激光具有重复频率高、平均功率高、单脉冲能量高的特点,能满足于市场应用需求。(The invention provides a sub-nanosecond green laser, which comprises: the device comprises a sub-nanosecond seed source for emitting seed light, a multistage amplification structure for performing multistage amplification on the seed light and a frequency doubling conversion structure for performing frequency doubling conversion on the amplified seed light; the multistage amplification structure comprises a first-stage amplification light path, a second-stage amplification light path and a third-stage amplification light path; the first-stage amplification light path comprises a first seed light path, a first laser crystal, a 0-degree reflector and a first pumping module which are sequentially arranged; the second-stage amplification light path comprises a second seed light path, a second laser crystal, a 0-degree reflector and a second pumping module which are sequentially arranged; the third-stage amplification light path comprises a third sub-light path, a third laser crystal, a pumping spectroscope and a third pumping module which are sequentially arranged. The subnanosecond green laser provided by the invention has the characteristics of high repetition frequency, high average power and high single pulse energy, and can meet the market application requirements.)

1. A sub-nanosecond green laser, comprising:

the device comprises a sub-nanosecond seed source for emitting seed light, a multistage amplification structure for performing multistage amplification on the seed light and a frequency doubling conversion structure for performing frequency doubling conversion on the amplified seed light;

the multistage amplification structure comprises a first stage amplification light path for carrying out primary amplification on the seed light, a second stage amplification light path for carrying out secondary amplification and a third stage amplification light path for carrying out tertiary amplification;

the first-stage amplification light path comprises a first seed light path, a first laser crystal, a 0-degree reflector and a first pumping module which are sequentially arranged;

the second-stage amplification light path comprises a second seed light path, a second laser crystal, a 0-degree reflector and a second pumping module which are sequentially arranged;

the third-stage amplification light path comprises a third sub-light path, a third laser crystal, a pumping spectroscope and a third pumping module which are sequentially arranged.

2. The sub-nanosecond green laser device according to claim 1, wherein the first sub optical path comprises a collimating mirror, a 45 ° reflecting mirror, a first plano-convex lens, a first plano-concave lens, an isolator, a half-wave plate, a 45 ° reflecting mirror and an optical compensation mirror, which are arranged in sequence.

3. The sub-nanosecond green laser device as claimed in claim 1, wherein the first pumping module comprises a first pumping focusing lens, a pumping return light protection lens, a first pumping collimating lens and a first pumping amplifying module, which are sequentially arranged.

4. The sub-nanosecond green laser device according to claim 1, wherein the second seed optical path comprises a 45 ° reflector, a second plano-convex lens, a second plano-concave lens, an isolator, a half-wave plate, a 45 ° reflector and an optical compensation mirror, which are sequentially arranged.

5. The sub-nanosecond green laser device as claimed in claim 1, wherein the second pumping module comprises a second pumping focusing lens, a pumping return light protection lens, a second pumping collimating lens and a second pumping amplifying module, which are sequentially arranged.

6. The sub-nanosecond green laser according to claim 1, wherein the third sub-optical path comprises a 45 ° reflector, a third plano-convex lens, a third plano-concave lens, a 45 ° reflector, an isolator and a half-wave plate, which are arranged in sequence.

7. The sub-nanosecond green laser device as claimed in claim 1, wherein the third pumping module comprises a third pumping focusing lens, a pumping return light protection lens, a third pumping collimating lens and a third pumping amplifying module, which are sequentially arranged.

8. The sub-nanosecond green laser according to claim 1, wherein the frequency doubling conversion structure comprises a pre-conversion optical path, a frequency doubling crystal, and a post-conversion optical path.

9. The sub-nanosecond green laser device according to claim 8, wherein the pre-conversion optical path comprises a fourth plano-convex lens, a fourth plano-concave lens, a 45 ° reflector, a sampling mirror, an isolator and a half-wave plate, which are arranged in sequence.

10. The sub-nanosecond green laser device as claimed in claim 8, wherein the converted light path comprises a 532nm/1064nm spectroscope, a 1064 absorber, a 532nm/1064nm spectroscope, a fifth plano-convex lens, a fifth plano-concave lens, a 532nm/1064nm spectroscope and a window mirror, which are sequentially disposed.

Technical Field

The invention relates to the technical field of laser, in particular to a sub-nanosecond green laser.

Background

The subnanosecond green laser has the characteristics of short output wavelength, high processing precision and the like, and has wide application scenes in the fields of laser micromachining, laser medical treatment, nonlinear optics and the like.

The traditional all-solid sub-nanosecond green laser has low repetition frequency and is not suitable for market application. All-fiber sub-nanosecond green laser is also available in the market, but the single pulse energy is very small, and the cutting efficiency and the cost advantage are not achieved. Therefore, how to realize a sub-nanosecond green laser with high repetition frequency, high average power and high single pulse energy becomes an urgent problem to be solved.

Disclosure of Invention

The invention aims to provide a sub-nanosecond green laser, which solves the technical problem that the sub-nanosecond green laser with high repetition frequency, high average power and high single pulse energy is lacked in the prior art.

The purpose of the invention can be realized by the following technical scheme:

a sub-nanosecond green laser, comprising:

the device comprises a sub-nanosecond seed source for emitting seed light, a multistage amplification structure for performing multistage amplification on the seed light and a frequency doubling conversion structure for performing frequency doubling conversion on the amplified seed light;

the multistage amplification structure comprises a first stage amplification light path for carrying out primary amplification on the seed light, a second stage amplification light path for carrying out secondary amplification and a third stage amplification light path for carrying out tertiary amplification;

the first-stage amplification light path comprises a first seed light path, a first laser crystal, a 0-degree reflector and a first pumping module which are sequentially arranged;

the second-stage amplification light path comprises a second seed light path, a second laser crystal, a 0-degree reflector and a second pumping module which are sequentially arranged;

the third-stage amplification light path comprises a third sub-light path, a third laser crystal, a pumping spectroscope and a third pumping module which are sequentially arranged.

Alternatively,

the first sub light path comprises a collimating mirror, a 45-degree reflecting mirror, a first plano-convex lens, a first plano-concave lens, an isolator, a half-wave plate, a 45-degree reflecting mirror and an optical compensation mirror which are sequentially arranged.

Alternatively,

the first pumping module comprises a first pumping focusing lens, a pumping return light protecting lens, a first pumping collimating lens and a first pumping amplifying module which are sequentially arranged.

Alternatively,

the second seed light path comprises a 45-degree reflector, a second plano-convex lens, a second plano-concave lens, an isolator, a half-wave plate, a 45-degree reflector and an optical compensation mirror which are sequentially arranged.

Alternatively,

the second pumping module comprises a second pumping focusing lens, a pumping return light protecting lens, a second pumping collimating lens and a second pumping amplifying module which are sequentially arranged.

Alternatively,

the third sub-optical path comprises a 45-degree reflector, a third plano-convex lens, a third plano-concave lens, a 45-degree reflector, an isolator and a half-wave plate which are arranged in sequence.

Alternatively,

the third pumping module comprises a third pumping focusing lens, a pumping return light protecting lens, a third pumping collimating lens and a third pumping amplifying module which are sequentially arranged.

Alternatively,

the frequency doubling conversion structure comprises a light path before conversion, a frequency doubling crystal and a light path after conversion.

Alternatively,

the optical path before conversion comprises a fourth plano-convex lens, a fourth plano-concave lens, a 45-degree reflector, a sampling mirror, an isolator and a half-wave plate which are sequentially arranged.

Alternatively,

the converted light path comprises a 532nm/1064nm spectroscope, a 1064nm absorber, a 532nm/1064nm spectroscope, a fifth plano-convex lens, a fifth plano-concave lens, a 532nm/1064nm spectroscope and a window mirror which are arranged in sequence.

The invention provides a sub-nanosecond green laser, which comprises: the device comprises a sub-nanosecond seed source for emitting seed light, a multistage amplification structure for performing multistage amplification on the seed light and a frequency doubling conversion structure for performing frequency doubling conversion on the amplified seed light; the multistage amplification structure comprises a first-stage amplification light path, a second-stage amplification light path and a third-stage amplification light path; the first-stage amplification light path comprises a first seed light path, a first laser crystal, a 0-degree reflector and a first pumping module which are sequentially arranged; the second-stage amplification light path comprises a second seed light path, a second laser crystal, a 0-degree reflector and a second pumping module which are sequentially arranged; the third-stage amplification light path comprises a third sub-light path, a third laser crystal, a pumping spectroscope and a third pumping module which are sequentially arranged.

The subnanosecond green laser provided by the invention has the beneficial effects that:

seed light emitted by the seed source sequentially passes through the first-stage amplification light path, the second-stage amplification light path and the third-stage amplification light path to be subjected to first-stage amplification, second-stage amplification and third-stage amplification respectively, and the seed light subjected to the third-stage amplification is subjected to frequency doubling conversion outside the cavity, so that sub-nanosecond green laser with high repetition frequency, high average power and high single-pulse energy can be output. The sub-nanosecond green laser obtained by the sub-nanosecond green laser provided by the invention has good laser beam quality, the repetition frequency is higher than that of an all-solid sub-nanosecond laser, the repetition frequency can reach more than 100KHz, the output power can reach more than 50W, the single-pulse energy is more than 500 muJ, and the single-pulse energy is far higher than that of an all-fiber sub-nanosecond laser, so that the market application requirement can be met.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic diagram of the optical path of the present invention;

FIG. 2 is a schematic structural view of the present invention;

FIG. 3 is a schematic diagram of a multi-stage enlarged structure of the present invention;

FIG. 4 is a schematic diagram of the first stage amplifying optical path according to the present invention;

FIG. 5 is a schematic diagram of the second stage amplifying optical path according to the present invention;

FIG. 6 is a schematic diagram of a third stage amplifying optical path according to the present invention;

FIG. 7 is a schematic structural diagram of a frequency doubling conversion structure according to the present invention;

wherein, the collimating lens 1, the 45 degree reflector 2, the first plano-convex lens 3, the first plano-concave lens 4, the isolator 5, the half-wave plate 6, the optical compensation mirror 7, the first laser crystal 8, the 0 degree reflector 9, the first pumping focusing mirror 10, the pumping return light protection mirror 11, the first pumping collimating mirror 12, the second plano-convex lens 13, the second plano-concave lens 14, the second laser crystal 15, the second pumping focusing mirror 16, the second pumping collimating mirror 17, the third plano-convex lens 18, the third plano-concave lens 19, the third laser crystal 20, the pumping spectroscope 21, the third pumping focusing mirror 22, the third pumping collimating mirror 23, the fourth plano-convex lens 24, the fourth plano-concave lens 25, the sampling mirror 26, the frequency doubling crystal 27, the 532nm/1064nm spectroscope 28, the fifth plano-convex lens 29, the fifth plano-concave lens 30, the window mirror 31, the first pumping amplification module 32, the second pumping amplification module 33, the optical fiber laser comprises a third pumping amplification module 34, a 1064nm absorber 35, a first seed optical path 101, a first pumping module 102, a second seed optical path 201, a second pumping module 202, a third seed optical path 301, a third pumping module 302, a pre-conversion optical path 401 and a post-conversion optical path 402.

Detailed Description

The embodiment of the invention provides a sub-nanosecond green laser, which aims to solve the technical problem that the sub-nanosecond green laser with high repetition frequency, high average power and high single pulse energy is lacked in the prior art.

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The subnanosecond pulse laser is a laser with the pulse width smaller than 1ns, has narrower pulse width and higher peak power compared with the traditional Q-switched laser, and has very wide application scenes in the fields of micro-processing and manufacturing, laser medical treatment and diagnosis, nonlinear optics and other scientific researches. The narrow pulse width and single longitudinal mode output of the device can be used for high-precision distance measurement and three-dimensional imaging; the high peak power and the high repetition frequency of the optical fiber can be used for research on laser-induced spectroscopy and nonlinear optics; and obtaining the sub-nanosecond 532nm green laser in a frequency doubling mode. In the fields of ocean exploration and underwater communication, green light with narrow pulse width is an important application light source due to the weak water absorbability of blue-green, and the pulse repetition rate and the energy stability of a green laser play a main role in defining the quantity and the chemical properties of ablative aerosol. Therefore, the subnanosecond laser with high repetition frequency and high average power has important scientific research value and has urgent requirements for market processing application.

Common subnanosecond pulse laser generation methods include passive Q-switched microchip lasers, short-cavity electro-optic Q-switched lasers, mode-locked lasers, cavity emptying, SBS compressed pulse width, electro-modulated semiconductor lasers and the like, but the power and energy directly output are low, and the application field is narrow.

And the traditional all-solid sub-nanosecond green laser has lower repetition frequency and is not suitable for market application. All-fiber sub-nanosecond green lasers are also available in the market, but the single pulse energy is very small, and the cutting efficiency and the cost advantage are not achieved. Therefore, the development of a sub-nanosecond green laser with high repetition frequency, high average power and high single pulse energy is particularly important, and the method has a large market.

Referring to fig. 1 and 2, the following is an embodiment of a sub-nanosecond green laser according to the present invention, including:

the device comprises a sub-nanosecond seed source for emitting seed light, a multistage amplification structure for performing multistage amplification on the seed light and a frequency doubling conversion structure for performing frequency doubling conversion on the amplified seed light;

the multistage amplification structure comprises a first stage amplification light path for carrying out primary amplification on the seed light, a second stage amplification light path for carrying out secondary amplification and a third stage amplification light path for carrying out tertiary amplification;

the first-stage amplification light path comprises a first seed light path 101, a first laser crystal, a 0-degree reflector and a first pumping module 102 which are sequentially arranged;

the second-stage amplification light path comprises a second seed light path 201, a second laser crystal, a 0-degree reflector and a second pumping module 202 which are sequentially arranged;

the third-stage amplification light path comprises a third sub-light path 301, a third laser crystal, a pumping spectroscope and a third pumping module 302 which are sequentially arranged.

In this embodiment, the sub-nanosecond seed source is used to emit seed light, specifically, the sub-nanosecond seed source emits sub-nanosecond laser having a high repetition frequency, and the sub-nanosecond laser having the high repetition frequency is used as the seed light. In a preferred embodiment, a MOPA fiber laser is used as a seed source. Of course, according to actual requirements, the MOPA fiber laser can be flexibly replaced by different types of seed sources such as a passive Q-switched microchip laser, a short-cavity electro-optical Q-switched laser, an electro-modulated semiconductor laser and the like.

Referring to fig. 3, in the present embodiment, the multi-stage amplifying structure includes a first stage amplifying optical path for performing first-stage amplification on the seed light, a second stage amplifying optical path for performing second-stage amplification, and a third stage amplifying optical path for performing third-stage amplification.

Referring to fig. 4, the first-stage amplifying optical path includes a first sub optical path 101, a first laser crystal 8, a 0 ° reflector, and a first pump module 102, which are sequentially disposed; the second-stage amplification light path comprises a second seed light path 201, a second laser crystal, a 0-degree reflector and a second pumping module 202 which are sequentially arranged; the third-stage amplification optical path comprises a third sub optical path 301, a third laser crystal, a pumping spectroscope and a third pumping module 303 which are arranged in sequence.

Specifically, the first sub optical path 101 includes a collimator lens 1, a 45 ° mirror 2, a first plano-convex lens 3, a first plano-concave lens 4, an isolator 5, a half-wave plate 6, the 45 ° mirror 2, and an optical compensation mirror 7, which are sequentially arranged.

Wherein, two surfaces of the collimating mirror 1 are coated with films HT1064, laser emitted from a sub-nanosecond seed source, namely seed light, is a point light source, and the collimating mirror 1 is utilized to perform beam shaping on the seed light; a 1064nm high-reflection film is plated on one surface of the 45-degree reflector 2, the light path is folded by 90 degrees, and the intracavity space of the laser can be reduced; a 1064nm high-transmittance film is plated on the two sides of the first plano-convex lens 3 and the first plano-concave lens 4 to shape the light beam output by the seed source; the windows at the two sides of the isolator 5 are plated with 1064nm high-transmittance films, so that the optical devices of the seed source are protected, meanwhile, the influence of spontaneous emission (ASE) light generated by a first-stage amplification light path on the seed source can be reduced, and the stability of the seed source is improved; the half-wave plate 6 is plated with 1064nm high-transmittance films on two sides and used for adjusting the polarization direction of the seed light beam; the optical compensation mirror 7 is used to compensate the thermal lens effect of the first laser crystal 8, and the focal length thereof is the equivalent thermal lens focal length of the first laser crystal 8. Preferably, the optical compensation mirror 7 is a plano-concave mirror, and the radius of curvature of the concave surface of the optical compensation mirror can be flexibly adjusted according to the focal length of the equivalent thermal lens of the first laser crystal 8, so as to directly compensate the thermal lens effect of the first laser crystal 8.

The first laser crystal 8 is Nd with a Nd ion doping concentration of 0.3%: two end faces of the YVO4 crystal are plated with anti-reflection films of pump light 1064nm/880 nm.

The 0-degree reflector 9 is plated with an anti-reflection film of 808nm/880nm and a high-reflection film of 1064nm, so that the seed light beams can be totally reflected, and the pumping light can be totally transmitted.

The first pumping module 102 includes a first pump focusing lens 10, a pump return light protecting lens 11, a first pump collimating lens 12, and a first pump amplifying module 32, which are sequentially disposed. The first pumping amplification module 32 performs first-stage amplification by using laser pumping with a central wavelength of 878.6 nm; 808nm/880nm antireflection films are plated on two surfaces of the first pump focusing mirror 10, 808nm/880nm antireflection films and 1064nm high-reflection films are respectively plated on two surfaces of the pump return light protection mirror 11, and 808nm/880nm antireflection films are plated on two surfaces of the first pump collimating mirror 12. The first pump focusing lens 10, the pump return light protecting lens 11 and the first pump collimating lens 12 form a first pump coupling system to perform primary shaping on pump light.

Referring to fig. 5, the second seed optical path 201 includes a 45 ° reflector 2, a second plano-convex lens 13, a second plano-concave lens 14, an isolator 5, a half-wave plate 6, a 45 ° reflector 2, and an optical compensation mirror 7, which are sequentially disposed.

Wherein, a 1064nm high-reflection film is plated on one surface of the 45-degree reflector 2, the light path is folded by 90 degrees, and the intracavity space of the laser can be reduced; a 1064nm high-transmittance film is plated on the two sides of the second plano-convex lens 13 and the second plano-concave lens 14, and the seed light after primary amplification of the first-stage amplification light path is shaped; the windows at the two sides of the isolator 5 are plated with 1064nm high-transmittance films, so that the optical device of the first-stage amplification light path is protected, the influence of spontaneous emission (ASE) light generated by the second-stage amplification light path on the optical device of the first-stage amplification light path can be reduced, and the stability of laser output can be improved on the whole; the half-wave plate 6 is plated with 1064nm high-transmittance films on two sides and used for adjusting the polarization direction of the seed light beam; the optical compensation mirror 7 is used to compensate the thermal lens effect of the second laser crystal 15, and the focal length thereof is the equivalent thermal lens focal length of the second laser crystal 15. Preferably, the optical compensation mirror 7 is a plano-concave mirror, and the radius of curvature of the concave surface of the optical compensation mirror can be flexibly adjusted according to the focal length of the equivalent thermal lens of the second laser crystal 15, so as to directly compensate the thermal lens effect of the second laser crystal 15.

The second laser crystal 15 is Nd with a Nd ion doping concentration of 0.3%: two end faces of the YVO4 crystal are plated with anti-reflection films of pump light 1064nm/880 nm.

The 0-degree reflector 9 is plated with an anti-reflection film of 808nm/880nm and a high-reflection film of 1064nm, so that the seed light beams can be totally reflected at 0 degree, and the pumping light can be totally transmitted.

The second pumping module 202 includes a second pump focusing lens 16, a pump return light protecting lens 11, a second pump collimating lens 17, and a second pump amplifying module 33, which are sequentially disposed. The second pumping amplification module 33 performs secondary amplification by using laser pumping with the central wavelength of 878.6 nm; 808nm/880nm antireflection films are plated on two surfaces of the second pump focusing mirror 16, 808nm/880nm antireflection films and 1064nm high-reflection films are respectively plated on two surfaces of the pump return light protection mirror 11, and 808nm/880nm antireflection films are plated on two surfaces of the second pump collimating mirror 17. The second pump focusing lens 16, the pump return light protecting lens 11 and the second pump collimating lens 17 form a second pump coupling system, and perform secondary shaping on the pump light.

It will be appreciated that the first stage amplification path and the second stage amplification path are very similar in structure and belong to the dual-pass amplification. The working process of the first-stage amplification light path is as follows: sub-nanosecond seed light emitted by a seed source enters a collimating mirror 1, is subjected to 90-degree light path deflection through a 45-degree reflecting mirror 2, is shaped through a first plano-convex lens 3 and a first plano-concave lens 4, is focused on the end face of a first laser crystal 8 through an isolator 5, a half-wave plate 6, the 45-degree reflecting mirror 2 and an optical compensation mirror 7 in sequence, is subjected to first single-pass amplification through the first laser crystal 8, is totally reflected to the end face of the first laser crystal 8 through a 0-degree reflecting mirror 9, is reflected through the 0-degree reflecting mirror after the first single-pass amplification, and returns to the original path to be subjected to second amplification through the first laser crystal 8, so that a double-pass amplification structure is formed. Meanwhile, the pumping light is shaped through the first pumping amplification module 32 and the first pumping coupling system, the shaped pumping light is focused on the end face of the first laser crystal 8 through the 0-degree reflector 9, the energy of the shaped pumping light is continuously absorbed and stored by the laser crystal, and when the seed light is focused on the end face of the first laser crystal 8, the laser crystal extracts the energy to perform first-stage amplification on the seed light.

The seed light amplified in the first stage in two ways compensates the thermal lens effect of the laser crystal by using the optical compensation mirror 7, sequentially passes through the 45-degree reflector 2, the half-wave plate 6 and the isolator 5, can reduce the influence of the first stage amplification on the seed source, then enters the second stage amplification light path through the 45-degree reflector 2, the second stage amplification process is similar to the first stage amplification process, and the seed light amplified in the second stage in two ways enters the third stage amplification light path.

Referring to fig. 6, the third-stage amplification optical path includes a third sub optical path 301, a third laser crystal 20, a pumping beam splitter 21, and a third pumping module 302, which are sequentially disposed. The third sub optical path 301 includes a 45 ° mirror 2, a third plano-convex lens 22, a third plano-concave lens 23, the 45 ° mirror 2, an isolator 5, and a half-wave plate 6, which are arranged in this order.

The third laser crystal 20 is Nd with a Nd ion doping concentration of 0.3%: two end faces of the YVO4 crystal are plated with anti-reflection films of pump light 1064nm/880 nm.

808nm/880nm antireflection films and 1064nm high-reflection films are plated on two surfaces of the pumping spectroscope 21, the seed light beam after secondary amplification is totally reflected by 45 degrees, the pumping light is totally transmitted, and the light path of the seed light can be folded by 90 degrees.

The windows at two sides of the isolator 5 are plated with 1064nm high-transmittance films, so that the optical device of the second-stage amplification light path is protected, meanwhile, the influence of spontaneous emission (ASE) light generated by the third-stage amplification light path on the optical device of the second-stage amplification light path can be reduced, and the stability of laser output can be improved on the whole.

The third pumping module 302 includes a third pump focusing lens 22, a pump return light protecting lens 11, a third pump collimating lens 23, and a third pump amplifying module 34, which are sequentially disposed. The third pumping amplification module 34 performs three-level amplification by using laser pumping with a central wavelength of 878.6 nm; 808nm/880nm antireflection films are plated on two surfaces of the third pump focusing mirror 22, 808nm/880nm antireflection films and 1064nm high-reflection films are respectively plated on two surfaces of the pump return light protection mirror 11, and 808nm/880nm antireflection films are plated on two surfaces of the third pump collimating mirror 23. The third pump focusing lens 22, the pump return light protecting lens 11 and the third pump collimating lens 23 form a third pump coupling system, and perform three-stage shaping on the pump light.

It is understood that the third stage amplification optical path is a single pass amplification of the second stage amplified seed light. The working process of the third-stage amplification light path is as follows: the seed light beam after the second-stage amplification is subjected to 90-degree light path deflection through the 45-degree reflector 2, then is shaped through the third plano-convex lens 18 and the third plano-concave lens 19, then sequentially passes through the 45-degree reflector 2, the isolator 5 and the half-wave plate 6 and is focused on the end face of the third laser crystal 20, the seed light beam is subjected to three-stage single-pass amplification (both the first-stage and the second-stage are double-pass amplification) through the third laser crystal 20, and then is subjected to 90-degree light path deflection through the pumping spectroscope 21 and is reflected to the frequency doubling conversion structure.

It is understood that the amplification-stage laser crystal in the present embodiment includes: a first laser crystal 8, a second laser crystal 15 and a third laser crystal 20, the amplification laser crystal is used as the gain medium of the laser for absorbing the pump light and generating the laser output, the host material is yttrium lithium fluoride, vanadate, YAG crystal, glass or ceramic, at least one kind of active ion is doped in the host material, the active ion is Nd³⁺、Yb³⁺、Cr³⁺Or Tm³⁺。

It should be noted that in the first pump amplification module 32, the second pump amplification module 33, and the third pump amplification module 34, the pump source is a semiconductor laser, and the pumping mode is end pumping or side pumping. The first pump amplification module 32 performs first-stage amplification on the pump light, the second pump amplification module 33 performs second-stage amplification on the pump light, and the third pump amplification module 34 performs third-stage amplification on the pump light, wherein each stage of amplification can adopt single-pass amplification or multi-pass amplification, and can be flexibly adjusted according to the requirement on laser power.

Referring to fig. 7, in the present embodiment, the frequency doubling conversion structure includes a pre-conversion optical path 401, a frequency doubling crystal, and a post-conversion optical path 402. The optical path before conversion comprises a fourth plano-convex lens 24, a fourth plano-concave lens 25, a 45-degree reflector 2, a sampling mirror 26, an isolator 5 and a half-wave plate 6 which are sequentially arranged; the converted light path comprises a 532nm/1064nm spectroscope 28, a 1064nm absorbent 35, a 532nm/1064nm spectroscope 28, a fifth plano-convex lens 29, a fifth plano-concave lens 30, a 532nm/1064nm spectroscope 28 and a window mirror 31 which are arranged in sequence.

Wherein, 1064nm antireflection coatings are plated on two surfaces of the sampling mirror 26, and the sampling mirror is placed at an angle of 56 degrees with the light path and used for power monitoring. Specifically, when power monitoring is performed, the laser state detection board may be used to perform photoelectric detection on the light reflected by the sampling mirror 26.

In a preferred embodiment, the frequency doubling crystal 27 is an LBO crystal with θ 90/Phi 11.2 °, and both end faces thereof are coated with 1064nm/532nm antireflection films for absorbing 1064nm fundamental frequency light and generating 532nm green laser output, and the host material may be KTP, LBO, bbp, KDP, or other crystals.

A532 nm/1064nm spectroscope 28 is coated with a 1064nm high-transmittance film and a 532nm high-reflectance film, and can split beams of 1064nm and 532nm, namely, laser with the reflection wavelength of 532nm and laser with the transmission wavelength of 1064 nm.

The 1064nm absorber 35 is coated with a 1064nm high-transmittance film, and the focal length of the plano-concave mirror is very short, so that the 1064nm laser transmitted through the 532nm/1064nm spectroscope 28 is scattered and absorbed.

The fifth plano-convex lens 29 and the fifth plano-concave lens 30 are used as beam shaping modules, 532nm high-transmittance films are plated on two sides, and the beams output after frequency doubling conversion are shaped.

The window mirror 31 is plated with a 532nm antireflection film to isolate the laser cavity from the outside.

It can be understood that the seed light after the three-stage amplification is 1064nm infrared fundamental frequency light with high repetition frequency, high power and narrow pulse width, and enters the frequency doubling crystal 27 through a light path before conversion for frequency doubling; the mixed laser passing through the frequency doubling crystal 27 includes un-doubled infrared fundamental light with a wavelength of 1064nm and green laser with a wavelength of 532nm, and the mixed laser reflects the fundamental light with the wavelength of 1064nm by a planar beam splitter such as a 532nm/1064nm beam splitter 28, and converts the pure green laser with the wavelength of 532nm to output through a light path. Meanwhile, the 1064nm absorber 35 may be used to diffuse the fundamental frequency light having an absorption wavelength of 1064 nm.

The subnanosecond green laser provided by the embodiment of the invention takes a subnanosecond MOPA fiber laser capable of realizing high repetition frequency as a seed source, seed light emitted by the seed source sequentially passes through a first-stage amplification light path, a second-stage amplification light path and a third-stage amplification light path to be subjected to first-stage amplification, second-stage amplification and third-stage amplification respectively, and the seed light subjected to the third-stage amplification is subjected to extra-cavity frequency multiplication conversion, so that the subnanosecond green laser with high repetition frequency, high average power, high single pulse energy and narrow pulse width can be output. The sub-nanosecond green laser obtained by the sub-nanosecond green laser provided by the invention has good laser beam quality, the repetition frequency is higher than that of an all-solid sub-nanosecond laser, the repetition frequency can reach more than 100KHz, the output power can reach more than 50W, and the single-pulse energy is far higher than that of an all-fiber sub-nanosecond laser, so that the market application requirements can be met.

According to the subnanosecond green laser provided by the embodiment of the invention, multiple groups of 45-degree reflectors and 0-degree reflectors are adopted in the cavity to turn the light path, so that the laser structure is more compact, and the space volume is saved; each stage of amplification light path carries out beam shaping on the light beam, and the energy in the laser crystal is fully extracted by adopting end pumping; the first-stage amplification light path and the second-stage amplification light path adopt a coaxial two-way amplification mode, and optical compensation lenses are adopted to perform optical compensation on the first-stage amplification light path and the second-stage amplification light path, so that the amplification efficiency is high, and the output laser beam quality is good; because the amplification efficiency of the on-axis amplification is higher than that of the off-axis amplification, the on-axis amplification mode is different from the off-axis amplification mode generally adopted in the market, and the sub-nanosecond green laser provided by the embodiment of the invention adopts the on-axis amplification mode, so that the amplification efficiency of the sub-nanosecond green laser provided by the embodiment of the invention is higher than that of the laser adopting the off-axis amplification mode in the market. According to the subnanosecond green laser provided by the embodiment of the invention, the isolator is used between the two adjacent stages of amplification light paths to protect the light paths, so that optical devices of the light paths are prevented from being damaged by return light and reflection, meanwhile, the generated spontaneous emission light (ASE light) is prevented from influencing the stability of the previous stage of amplification light paths, and the stability of output laser is integrally improved.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.