Fiber laser and green laser device

Abstract

The embodiment of the invention discloses an optical fiber laser and a green laser device. The fiber laser comprises a seed source and at least one stage of fiber amplifier. The seed source comprises a first pumping source, a first pumping beam combiner, a first fiber bragg grating, a first ytterbium-doped fiber, a second fiber bragg grating and a second ytterbium-doped fiber; the optical fiber amplifier comprises a second pumping source, a second pumping beam combiner and a third ytterbium-doped optical fiber; the second pumping source comprises a third pumping source, a third pumping beam combiner, a third fiber bragg grating, a fourth ytterbium-doped fiber and a fourth fiber bragg grating. The optical fiber laser provided by the embodiment of the invention adopts a cascade pumping technology, so that the power and brightness of fundamental frequency laser output by the narrow linewidth optical fiber laser are effectively improved, the nonlinear effect of the fundamental frequency laser and the thermal load of the optical fiber are remarkably reduced, and the beam quality and output power of the fundamental frequency laser are remarkably improved; and a foundation is laid for higher green light output.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular to an optical fiber laser and a green light laser device. Background Art

[0002] Copper material is one of the most widely used metal materials in modern industrial processing. The terminal demand structure of the copper industry chain covers more than 30 sub-industries such as aerospace, high-speed trains, smart terminal products, electronic communications, and automobiles, and is the main indicator of high-end industrial applications. The 1000nm infrared fiber laser currently used on a large scale has shortcomings such as large spatter and uncontrollable melting depth in the processing of copper materials due to the weak absorption of copper. At room temperature, copper has an absorption rate of less than 5% for near-infrared wavelengths (about 1000nm), so the efficiency of using infrared light to process copper is extremely low, 95% of the laser will be reflected, and it will also damage the laser itself; while copper has an absorption rate of more than 40% for green light wavelengths (515nm~532nm). The selectivity of the material itself for laser wavelengths determines that the most ideal wavelength for precision processing of high-reflectivity materials is a short wavelength (≤700nm).

[0003] Green wavelength lasers are usually generated by frequency doubling. A 532nm frequency-doubled laser can be generated by frequency doubling a 1064nm fundamental frequency laser. However, the 1064nm laser in the prior art has the problems of poor beam quality and low output power, making it difficult to achieve high-power, high-efficiency frequency-doubled laser output. Summary of the invention

[0004] The embodiments of the present invention provide a fiber laser and a green light laser device. The fiber laser adopts cascade pumping technology, which effectively improves the power and brightness of the fundamental frequency laser output by the narrow linewidth fiber laser, significantly reduces the nonlinear effect of the fundamental frequency laser and the thermal load of the optical fiber, significantly improves the beam quality and output power of the fundamental frequency laser, lays a foundation for higher green light output, and realizes green light laser output with high frequency doubling efficiency, high brightness, narrow linewidth, small quantum loss, low optical fiber thermal load, and high transverse mode instability (TMI) threshold.

[0005] According to one aspect of the present invention, there is provided a fiber laser, comprising a seed source and at least one stage of fiber amplifier;

[0006] The seed source comprises a first pump source, a first pump combiner, a first fiber Bragg grating, a first ytterbium-doped fiber, a second fiber Bragg grating and a second ytterbium-doped fiber which are connected in sequence, the first fiber Bragg grating, the first ytterbium-doped fiber and the second fiber Bragg grating form a first resonant cavity, the first pump light output by the first pump source is incident on the first resonant cavity after passing through the first pump combiner, a part of the first pump light is incident on the second ytterbium-doped fiber after passing through the first resonant cavity, and the seed light output by the first resonant cavity is pre-amplified by the second ytterbium-doped fiber and then output to the fiber amplifier;

[0007] The optical fiber amplifier comprises a second pump source, a second pump combiner and a third ytterbium-doped optical fiber, wherein the output end of the second pump source is connected to the pump input end of the second pump combiner, the output end of the seed source is connected to the seed light input end of the second pump combiner, and the output end of the second pump combiner is connected to the first end of the third ytterbium-doped optical fiber;

[0008] The second pump source includes a third pump source, a third pump combiner, a third fiber Bragg grating, a fourth ytterbium-doped fiber and a fourth fiber Bragg grating. The output end of the third pump source is connected to the pump input end of the third pump combiner, the output end of the third pump combiner is connected to the first end of the third fiber Bragg grating, the second end of the third fiber Bragg grating is connected to the first end of the fourth ytterbium-doped fiber, the second end of the fourth ytterbium-doped fiber is connected to the first end of the fourth fiber Bragg grating, the third fiber Bragg grating, the fourth ytterbium-doped fiber and the fourth fiber Bragg grating form a second resonant cavity, the third pump light output by the third pump source passes through the third pump combiner and is incident on the second resonant cavity to output a second pump light, the wavelength of the first pump light and the wavelength of the third pump light are both smaller than the wavelength of the second pump light, and the wavelength of the second pump light is smaller than the wavelength of the seed light.

[0009] Optionally, an isolator is further included, wherein the input end of the isolator is connected to the output end of the seed source, and the output end of the isolator is connected to the input end of the optical fiber amplifier.

[0010] Optionally, the optical fiber amplifier further includes a first cladding light stripper, and an input end of the first cladding light stripper is connected to the second end of the third ytterbium-doped optical fiber.

[0011] Optionally, the seed source further includes a second cladding light stripper, and an input end of the second cladding light stripper is connected to the second end of the second ytterbium-doped optical fiber.

[0012] Optionally, it also includes a QBH optical fiber connector arranged at the output end of the optical fiber laser.

[0013] Optionally, the first pump source and the third pump source are both semiconductor lasers with an output wavelength of 976nm, the second pump source is a fiber laser with an output wavelength of 1018nm and an output power of 1300W to 1500W, and the seed source is a fiber laser with an output wavelength of 1064nm and an output power of 20W to 30W.

[0014] According to another aspect of the present invention, there is provided a green laser device, comprising a fundamental frequency light source, a beam adjustment module, a frequency doubling crystal and an output module, wherein the fundamental frequency light source is the above-mentioned fiber laser, the beam adjustment module comprises a lens and a half wave plate, and the output module comprises a dichroic mirror;

[0015] The fundamental frequency light source outputs a fundamental frequency beam of 1064 nm, which is incident on the frequency doubling crystal after being converged by the lens and adjusted in polarization state by the half wave plate, and then outputs a frequency doubling beam of 532 nm. The dichroic mirror is used to split the frequency doubling beam and part of the fundamental frequency beam into different transmission directions.

[0016] Optionally, the first output end of the dichroic mirror outputs the frequency-doubled light beam, and the second output end of the dichroic mirror outputs the fundamental frequency light beam. The output module also includes a reflector arranged at the first output end of the dichroic mirror and a light absorption unit arranged at the second output end of the dichroic mirror, the reflector is used to change the transmission direction of the frequency-doubled light beam, and the light absorption unit is used to absorb the fundamental frequency light beam that has not been frequency-doubled.

[0017] Optionally, the beam adjustment module includes a collimating lens, a half wave plate and a focusing lens, and the collimating lens, the half wave plate and the focusing lens are arranged in sequence along the direction of the fundamental frequency light source pointing to the frequency doubling crystal, the fundamental frequency light beam is collimated by the collimating lens, the half wave plate rotates the polarization direction of the fundamental frequency light beam, and the focusing lens focuses into the frequency doubling crystal.

[0018] Optionally, a temperature control module is further included, and the frequency doubling crystal is fixedly arranged on the temperature control module.

[0019] The fiber laser provided in the embodiment of the present invention comprises a seed source and at least one stage of fiber amplifier; the seed source comprises a first pump source, a first pump combiner, a first fiber Bragg grating, a first ytterbium-doped fiber, a second fiber Bragg grating and a second ytterbium-doped fiber; the first fiber Bragg grating, the first ytterbium-doped fiber and the second fiber Bragg grating form a first resonant cavity; the first pump light output by the first pump source is incident on the first resonant cavity after passing through the first pump combiner; part of the first pump light is incident on the second ytterbium-doped fiber after passing through the first resonant cavity; the seed light output by the first resonant cavity is pre-amplified by the second ytterbium-doped fiber and then output to The optical fiber amplifier comprises a second pump source, a second pump combiner and a third ytterbium-doped optical fiber, the second pump source comprises a third pump source, a third pump combiner, a third fiber Bragg grating, a fourth ytterbium-doped optical fiber and a fourth fiber Bragg grating, the third fiber Bragg grating, the fourth ytterbium-doped optical fiber and the fourth fiber Bragg grating form a second resonant cavity, the third pump light output by the third pump source is incident on the second resonant cavity after passing through the third pump combiner, and the second pump light is output, the wavelength of the first pump light and the wavelength of the third pump light are both smaller than the wavelength of the second pump light, and the wavelength of the second pump light is smaller than the wavelength of the seed light. First, a second pump light of an intermediate wavelength is generated by a third pump light of a short wavelength. The second pump light is used as the pump light of the fiber amplifier to amplify the seed light. That is, the cascade pumping technology is used to improve the power and brightness of the fundamental frequency laser output by the narrow linewidth fiber laser, which significantly reduces the nonlinear effect of the fundamental frequency laser and the thermal load of the optical fiber, and significantly improves the beam quality and output power of the fundamental frequency laser, laying the foundation for higher green light output, and achieving green light laser output with high frequency doubling efficiency, high brightness, narrow linewidth, small quantum loss, low optical fiber thermal load, and high TMI threshold.

[0020] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 A schematic diagram of the structure of a fiber laser provided by an embodiment of the present invention;

[0023] Figure 2 A schematic diagram of the structure of a seed source provided by an embodiment of the present invention;

[0024] Figure 3 A schematic structural diagram of a second pump source provided by an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of the structure of another fiber laser provided by an embodiment of the present invention;

[0026] Figure 5 A structural schematic diagram of another fiber laser is provided for an embodiment of the present invention;

[0027] Figure 6 A schematic diagram of the structure of another seed source is provided for an embodiment of the present invention;

[0028] Figure 7 A structural schematic diagram of another fiber laser is provided for an embodiment of the present invention;

[0029] Figure 8 A structural block diagram of a green laser device provided by an embodiment of the present invention;

[0030] Fig. 9 A schematic diagram of the structure of a green laser device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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 creative work should fall within the scope of protection of the present invention.

[0032] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0033] Figure 1 A schematic diagram of the structure of a fiber laser provided by an embodiment of the present invention, Figure 2 A schematic diagram of the structure of a seed source provided by an embodiment of the present invention, Figure 3 A schematic diagram of the structure of a second pump source provided by an embodiment of the present invention. Figure 1 The fiber laser provided in the embodiment of the present invention includes a seed source 10 and at least one optical fiber amplifier 20 ( Figure 1 The first-stage fiber amplifier is used as an example, which is not a limitation of the embodiments of the present invention. The seed source 10 is used to output seed light. For example, the seed light can be 1064nm infrared light, which is used to generate 532nm fundamental frequency light. In a certain embodiment, optionally, the seed source 10 is a fiber laser with an output wavelength of 1064nm and an output power of 20W to 30W. Figure 2 The seed source 10 includes a first pump source 11 ( Figure 2 In the figure, two first pump sources 11 are taken as an example. There is at least one first pump source 11, and there can be multiple first pump sources, which is not a limitation of the embodiments of the present invention), a first pump combiner 12, a first fiber Bragg grating 13, a first ytterbium-doped fiber 14, a second fiber Bragg grating 15 and a second ytterbium-doped fiber 16. Specifically, the output end of the first pump source 11 is connected to the pump input end of the first pump combiner 12, the output end of the first pump combiner 12 is connected to the first end of the first fiber Bragg grating 13, the second end of the first fiber Bragg grating 13 is connected to the first end of the first ytterbium-doped fiber 14, the second end of the first ytterbium-doped fiber 14 is connected to the first end of the second fiber Bragg grating 15, the second end of the second fiber Bragg grating 15 is connected to the first end of the second ytterbium-doped fiber 16, the first fiber Bragg grating 13, the first ytterbium-doped fiber 14 and the second fiber Bragg grating 15 form a first resonant cavity, the first pump light output by the first pump source 11 passes through the first pump combiner 12 and is incident on the first resonant cavity, part of the first pump light passes through the first resonant cavity and is incident on the second ytterbium-doped fiber 16, and the seed light output by the first resonant cavity is pre-amplified by the second ytterbium-doped fiber 16 and then output to the fiber amplifier 20.

[0034] Among them, the first fiber Bragg grating 13 can use a high reflectivity grating, for example, a reflectivity of ≥99.5%, and the second fiber Bragg grating 15 can use a low reflectivity grating, for example, a reflectivity of 10%. The central wavelength of the first fiber Bragg grating 13 and the second fiber Bragg grating 15 is set to 1064nm, and the first fiber Bragg grating 13 and the second fiber Bragg grating 15 build an ultra-short first resonant cavity. The line width of the seed source 10 is mainly affected by two factors, one is the 3dB bandwidth of the fiber Bragg grating, which is generally a fixed parameter (0.05nm), and the other factor affecting the line width is the length of the optical fiber. Within a certain range, the shorter the optical fiber, the smaller the line width, but the optical fiber length cannot be reduced indefinitely, which will affect the output power of the seed laser. The theoretical length of the first ytterbium-doped optical fiber 14 can be 1.5m~3.0m, and can output seed light with a narrow line width (<0.2nm). Optionally, the first pump source 11 can be a semiconductor laser with an output wavelength of 976nm. The unabsorbed first pump light can be reabsorbed by the second ytterbium-doped fiber 16 outside the cavity to achieve pre-amplification of the seed light, thereby increasing the output power of the overall seed and achieving a narrow linewidth seed light output of about 20W to 30W. The output linewidth can be controlled within 0.1nm.

[0035] Continue to refer Figure 1 , the optical fiber amplifier 20 includes a second pump source 21 ( Figure 1 In the figure, two second pump sources 21 are taken as an example. There is at least one second pump source 21, and there can be multiple second pump sources 21, which is not a limitation of the embodiments of the present invention). The second pump combiner 22 and the third ytterbium-doped fiber 23, the output end of the second pump source 21 is connected to the pump input end of the second pump combiner 22, the output end of the seed source 10 is connected to the seed light input end of the second pump combiner 22, and the output end of the second pump combiner 22 is connected to the first end of the third ytterbium-doped fiber 23.

[0036] The third ytterbium-doped optical fiber 23 may be an ytterbium-doped optical fiber with a core diameter of 25 μm and a cladding diameter of 400 μm. The power of the seed light is amplified by the optical fiber amplifier 20 to achieve high-power 1064 nm laser output.

[0037] refer to Figure 3 , the second pump source 21 includes a third pump source 211 ( Figure 3In the embodiment, two third pump sources 211 are taken as an example. There is at least one third pump source 211, and there may be multiple third pump sources 211, which is not a limitation of the embodiment of the present invention), a third pump combiner 212, a third fiber Bragg grating 213, a fourth ytterbium-doped fiber 214 and a fourth fiber Bragg grating 215. The output end of the third pump source 211 is connected to the pump input end of the third pump combiner 212, the output end of the third pump combiner 212 is connected to the first end of the third fiber Bragg grating 213, and the second end of the third fiber Bragg grating 213 is connected to the fourth The first end of the ytterbium-doped fiber 214 is connected, the second end of the fourth ytterbium-doped fiber 214 is connected to the first end of the fourth fiber Bragg grating 215, the third fiber Bragg grating 213, the fourth ytterbium-doped fiber 214 and the fourth fiber Bragg grating 215 form a second resonant cavity, the third pump light output by the third pump source 211 passes through the third pump combiner 212 and is incident on the second resonant cavity, and the second pump light is output, the wavelength of the first pump light and the wavelength of the third pump light are both smaller than the wavelength of the second pump light, and the wavelength of the second pump light is smaller than the wavelength of the seed light.

[0038] Optionally, the third pump source 211 can also be a semiconductor laser with an output wavelength of 976nm, the third fiber Bragg grating 213 can be a high-reflectivity grating, and the fourth fiber Bragg grating 215 can be a low-reflectivity grating. The center wavelength of the third fiber Bragg grating 213 and the fourth fiber Bragg grating 215 is set to 1018nm, and the fourth ytterbium-doped fiber 214 can be an ytterbium-doped fiber with a core diameter of 30μm and a cladding diameter of 400μm, so as to form a fiber laser with an output wavelength of 1018nm and an output power of 1300W to 1500W.

[0039] The technical solution of the embodiment of the present invention is to first generate a second pump light of an intermediate wavelength (1018nm) by a third pump light of a short wavelength (976nm), and the second pump light is used as the pump light of the optical fiber amplifier to amplify the seed light (1064nm), that is, the cascade pumping technology is used to improve the power and brightness of the fundamental frequency laser output by the narrow linewidth fiber laser, which significantly reduces the nonlinear effect of the fundamental frequency laser and the thermal load of the optical fiber, and significantly improves the beam quality and output power of the fundamental frequency laser, laying the foundation for higher green light output, and realizing green light laser output with high frequency doubling efficiency, high brightness, narrow linewidth, small quantum loss, low optical fiber thermal load, and high TMI threshold.

[0040] Figure 4 A schematic diagram of another fiber laser structure provided by an embodiment of the present invention, referring to Figure 4 Optionally, the fiber laser further includes an isolator 30 , the input end of the isolator 30 is connected to the output end of the seed source 10 , and the output end of the isolator 30 is connected to the input end of the fiber amplifier 20 .

[0041] By providing the isolator 30 , it is possible to prevent the reflected light from damaging the components in the seed source 10 during the amplification process.

[0042] Figure 5 Another structural diagram of a fiber laser is provided for the embodiment of the present invention, referring to Figure 5 Optionally, the optical fiber amplifier 20 further includes a first cladding light stripper 24 , and an input end of the first cladding light stripper 24 is connected to the second end of the third ytterbium-doped optical fiber 23 .

[0043] The first cladding light stripper 24 is used to absorb the residual second pump light to improve the beam quality of the output light.

[0044] Figure 6 Another schematic diagram of the structure of a seed source is provided for the embodiment of the present invention, referring to Figure 6 Optionally, the seed source 10 further includes a second cladding light stripper 17 , and an input end of the second cladding light stripper 17 is connected to a second end of the second ytterbium-doped optical fiber 16 .

[0045] The second cladding light stripper 17 is used to absorb the residual first pump light to improve the beam quality of the seed light.

[0046] Optional, continue to refer to Figure 3 The second pump source 21 further includes a third cladding light stripper 216, an input end of the third cladding light stripper 216 is connected to the second end of the fourth fiber Bragg grating 215, and is used to absorb the residual third pump light.

[0047] Figure 7 Another structural diagram of a fiber laser is provided for the embodiment of the present invention, referring to Figure 7 Optionally, the fiber laser further includes a QBH fiber connector 40 disposed at the output end of the fiber laser.

[0048] QBH (Quartz Block Head) fiber connector 40 adopts the Quartz Block related patented technology and mode stripping technology of Optoskand AB of Sweden. It is a fiber connector with a built-in water cooling mechanism. It can handle extremely high laser power transmission (>5kW average power, MW-level pulse peak power) and can withstand very high echo reflection.

[0049] Figure 8 A structural block diagram of a green laser device provided by an embodiment of the present invention, refer to Figure 8The green laser device includes a fundamental frequency light source 100, a beam adjustment module 200, a frequency doubling crystal 300 and an output module 400. The fundamental frequency light source 100 is any one of the fiber lasers provided in the above embodiments. The beam adjustment module 200 includes a lens and a half-wave plate. The output module 400 includes a dichroic mirror. The fundamental frequency light source 100 outputs a fundamental frequency light beam of 1064 nm, which is incident on the frequency doubling crystal 300 after being converged by a lens and polarization state adjusted by a half-wave plate, and then outputs a frequency doubling light beam of 532 nm. The dichroic mirror is used to split the frequency doubling light beam and part of the fundamental frequency light beam into different transmission directions.

[0050] Among them, the fundamental frequency light source 100 is the optical fiber laser provided in the above embodiment, and uses cascade pumping technology to output a high-power, high-beam-quality fundamental frequency light beam; the beam adjustment module 200 adjusts the spot size and polarization state of the fundamental frequency light beam, and the fundamental frequency light beam converges to the frequency doubling crystal 300 to generate frequency doubling; the frequency doubling crystal 300 can be lithium triborate LBO, and the LBO crystal is a negative biaxial crystal with the advantages of wide band range, high efficiency, high damage threshold, etc.; the output module 400 is used to separate the frequency doubling light beam and the fundamental frequency light beam, and output a high-quality frequency doubling light beam.

[0051] The embodiment of the present invention proposes a solution to realize a high-power, high-beam-quality polarization-maintaining narrow-linewidth 1064nm laser using fiber Bragg grating and cascade pumping for main amplification technology, and output high-beam-quality, narrow-linewidth green light with a linewidth of ≤0.2nm after frequency doubling. The main amplification technology using fiber Bragg grating and cascade pumping can significantly improve the beam quality and linewidth performance of the fundamental frequency laser after the amplification stage, improve the stability of the fundamental frequency laser, and provide a good foundation for the output of high-power green light. The fundamental frequency light is adjusted to the optimal state by frequency doubling optimization after passing through the collimation and focusing system. Its main advantages are: it can realize high-beam-quality, narrow-linewidth green light laser output with a linewidth of ≤0.2nm, it has higher laser power stability, higher beam quality, and the entire green light system will also have better frequency doubling efficiency, which can realize industrial processing applications such as laser welding or 3D printing.

[0052] Fig. 9 A schematic diagram of the structure of a green laser device provided by an embodiment of the present invention, referring to Fig. 9 Optionally, the first output end of the dichroic mirror 401 outputs a frequency-doubled light beam, and the second output end of the dichroic mirror 401 outputs a fundamental frequency light beam. The output module 400 also includes a reflector 402 arranged at the first output end of the dichroic mirror 401 and a light absorption unit 403 arranged at the second output end of the dichroic mirror 401. The reflector 420 is used to change the transmission direction of the frequency-doubled light beam, and the light absorption unit 403 is used to absorb the fundamental frequency light beam that has not been frequency-doubled.

[0053] It is understandable that the frequency doubling efficiency of the frequency doubling crystal 300 cannot reach 100%, that is, part of the 1064nm fundamental frequency light beam cannot be absorbed by the frequency doubling crystal 300, and a light absorption unit 403 can be set to absorb the remaining 1064nm fundamental frequency light beam and convert it into heat energy. In specific implementation, the angle between the binocular mirror 401 and the reflector 402 and the optical axis can be set to 45°.

[0054] Continue to refer Fig. 9 Optionally, the beam adjustment module 200 includes a collimating lens 201, a half wave plate 202 and a focusing lens 203. The collimating lens 201, the half wave plate 202 and the focusing lens 203 are arranged in sequence along the direction of the fundamental frequency light source 100 pointing to the frequency doubling crystal 300. The fundamental frequency light beam is collimated by the collimating lens 201, the half wave plate 202 rotates the polarization direction of the fundamental frequency light beam, and the focusing lens 203 focuses into the frequency doubling crystal 300.

[0055] Continue to refer Fig. 9 Optionally, the green laser device further includes a temperature control module 500, and the frequency doubling crystal 300 is fixedly disposed on the temperature control module 500. The temperature control module 500 is used to maintain a stable temperature of the frequency doubling crystal 300 to maintain an optimal frequency doubling efficiency.

[0056] It can be understood that in order for the frequency doubling crystal 300 to produce frequency doubling, the fundamental frequency light beam needs to be converged onto the frequency doubling crystal 300, and the phase matching conditions for generating frequency doubling need to be met. The collimating lens 201 and the focusing lens 203 are used to converge the light beam, and the half wave plate 202 is used to adjust the polarization state to meet the phase matching conditions. During the installation and adjustment of the device, the position of the frequency doubling crystal 300 is adjusted to achieve the best frequency doubling efficiency. Since temperature changes will also affect the frequency doubling efficiency, the frequency doubling crystal 300 is fixedly set in the temperature control module 500 (in other embodiments, it can also be set on the surface of the temperature control module 500, and the embodiments of the present invention are not limited to this) to maintain the best frequency doubling efficiency.

[0057] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fiber laser, characterized in that: comprising a seed source and at least one stage of optical fiber amplifier; The seed source comprises a first pump source, a first pump combiner, a first fiber Bragg grating, a first ytterbium-doped fiber, a second fiber Bragg grating and a second ytterbium-doped fiber which are connected in sequence, the first fiber Bragg grating, the first ytterbium-doped fiber and the second fiber Bragg grating form a first resonant cavity, the first pump light output by the first pump source is incident on the first resonant cavity after passing through the first pump combiner, a part of the first pump light is incident on the second ytterbium-doped fiber after passing through the first resonant cavity, and the seed light output by the first resonant cavity is pre-amplified by the second ytterbium-doped fiber and then output to the fiber amplifier; The optical fiber amplifier comprises a second pump source, a second pump combiner and a third ytterbium-doped optical fiber, wherein the output end of the second pump source is connected to the pump input end of the second pump combiner, the output end of the seed source is connected to the seed light input end of the second pump combiner, and the output end of the second pump combiner is connected to the first end of the third ytterbium-doped optical fiber; The second pump source includes a third pump source, a third pump combiner, a third fiber Bragg grating, a fourth ytterbium-doped fiber and a fourth fiber Bragg grating. The output end of the third pump source is connected to the pump input end of the third pump combiner, the output end of the third pump combiner is connected to the first end of the third fiber Bragg grating, the second end of the third fiber Bragg grating is connected to the first end of the fourth ytterbium-doped fiber, the second end of the fourth ytterbium-doped fiber is connected to the first end of the fourth fiber Bragg grating, the third fiber Bragg grating, the fourth ytterbium-doped fiber and the fourth fiber Bragg grating form a second resonant cavity, the third pump light output by the third pump source passes through the third pump combiner and is incident on the second resonant cavity to output a second pump light, the wavelength of the first pump light and the wavelength of the third pump light are both smaller than the wavelength of the second pump light, and the wavelength of the second pump light is smaller than the wavelength of the seed light.

2. The fiber laser according to claim 1, characterized in that: It also includes an isolator, wherein the input end of the isolator is connected to the output end of the seed source, and the output end of the isolator is connected to the input end of the optical fiber amplifier.

3. The fiber laser according to claim 1, characterized in that: The optical fiber amplifier further comprises a first cladding light stripper, wherein an input end of the first cladding light stripper is connected to the second end of the third ytterbium-doped optical fiber.

4. The fiber laser according to claim 1, characterized in that: The seed source further includes a second cladding light stripper, and an input end of the second cladding light stripper is connected to the second end of the second ytterbium-doped optical fiber.

5. The fiber laser according to claim 1, characterized in that: It also includes a QBH optical fiber connector arranged at the output end of the optical fiber laser.

6. The fiber laser according to claim 1, characterized in that: The first pump source and the third pump source are both semiconductor lasers with an output wavelength of 976nm, the second pump source is a fiber laser with an output wavelength of 1018nm and an output power of 1300W to 1500W, and the seed source is a fiber laser with an output wavelength of 1064nm and an output power of 20W to 30W.

7. A green laser device, characterized in that: It comprises a fundamental frequency light source, a beam adjustment module, a frequency doubling crystal and an output module, wherein the fundamental frequency light source is the optical fiber laser according to any one of claims 1 to 6, the beam adjustment module comprises a lens and a half wave plate, and the output module comprises a dichroic mirror; The fundamental frequency light source outputs a fundamental frequency beam of 1064 nm, which is incident on the frequency doubling crystal after being converged by the lens and adjusted in polarization state by the half wave plate, and then outputs a frequency doubling beam of 532 nm. The dichroic mirror is used to split the frequency doubling beam and part of the fundamental frequency beam into different transmission directions.

8. The green laser device according to claim 7, characterized in that: The first output end of the dichroic mirror outputs the frequency-doubled light beam, and the second output end of the dichroic mirror outputs the fundamental frequency light beam. The output module also includes a reflector arranged at the first output end of the dichroic mirror and a light absorption unit arranged at the second output end of the dichroic mirror. The reflector is used to change the transmission direction of the frequency-doubled light beam, and the light absorption unit is used to absorb the fundamental frequency light beam that has not been frequency-doubled.

9. The green laser device according to claim 7, characterized in that: The beam adjustment module includes a collimating lens, a half wave plate and a focusing lens. The collimating lens, the half wave plate and the focusing lens are arranged in sequence along the direction in which the fundamental frequency light source points to the frequency doubling crystal. The fundamental frequency light beam is collimated by the collimating lens, the half wave plate rotates the polarization direction of the fundamental frequency light beam, and the focusing lens focuses into the frequency doubling crystal.

10. The green laser device according to claim 7, characterized in that: It also includes a temperature control module, and the frequency doubling crystal is fixedly arranged on the temperature control module.

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