High-power optical fiber green laser

Abstract

The invention provides a high-power optical fiber green laser, and belongs to the technical field of optical fiber lasers. The device specifically comprises a seed source module which is used for providing a seed light source with adjustable pulse width and repetition frequency and carrying out phase modulation and spectrum broadening on the seed light source; the primary amplification unit is in light path connection with the output end of the seed source module and is used for performing power amplification on seed light; the secondary amplification unit is in light path connection with the output end of the primary amplification unit and is used for performing power amplification on the signal light again; the third-stage amplification unit is in light path connection with the output end of the second-stage amplification unit and is used for performing third power amplification on the laser; and the frequency doubling output unit is connected with an output end light path of the three-stage amplification unit, and is used for carrying out frequency doubling on the laser subjected to the third power amplification and outputting green laser with a specified divergence angle and a light spot size. According to the invention, the SBS threshold is improved from two directions of phase modulation and optical fiber length shortening, so that the peak power output by the optical fiber green laser is higher.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber lasers, and in particular to a high-power optical fiber green light laser. Background Art

[0002] Green lasers have the characteristics of high single-photon energy, good beam quality, and strong material effects. They are widely used in industrial precision machining, material surface treatment, scientific research, military industry, biomedicine, and other fields. Especially with the rapid development of semiconductors, 3C, and new energy industries, green lasers have performed well in industrial metal material marking, copper material cutting, and scribing applications. At present, the products on the market are mainly solid green lasers, which use ytterbium-doped and neodymium-doped crystals as laser gain media. Through the technical route of intracavity or extracavity frequency doubling, it is easy to achieve high-peak and high-energy nanosecond green laser output. The structure is simple and compact, but the long-term working stability is poor, and many parameters such as pulse width and repetition rate cannot be flexibly adjusted. In addition, due to the limitation of the crystal heat dissipation capacity, the average power is low. The fiber green laser adopts a technical route that combines fiber fundamental frequency with solid-state frequency doubling. The fundamental frequency part uses polarization-maintaining fiber amplification to ensure the high polarization state of the fundamental frequency, thereby ensuring the frequency doubling efficiency. The fiber fundamental frequency adopts a MOPA structure, which can achieve high-precision seed waveform editing and output seed signals through software control. It has the advantages of adjustable repetition frequency and pulse width, high output average power, and good stability. The fundamental frequency light after fiber amplification is spatially collimated and output, and nonlinear crystals are used for frequency doubling. It has a simple structure and excellent beam quality, which greatly improves industrial processing efficiency.

[0003] Chinese utility model patent CN219801481U discloses a 150ps-2ns all-fiber green and ultraviolet laser modulated by two cascaded Mach-Zehnder intensity modulators. This technical solution improves the average power of the green laser to a certain extent. The shortcomings are: 1. The threshold of the stimulated Brillouin scattering effect in the optical fiber is not increased. When the optical fiber fundamental frequency power is amplified, the peak power is limited and the pulse width range only supports less than 2ns. 2. The frequency doubling structure is complex, and the frequency doubling efficiency is about 65% under multiple frequency doubling designs.

[0004] Therefore, it is very necessary to provide a high-power fiber green laser, analyze the threshold conditions of stimulated Brillouin scattering, increase the laser line width by phase modulation of the seed light, and shorten the fiber length of the main amplifier stage, thereby increasing the threshold of stimulated Brillouin scattering and greatly improving the peak power of the fiber green laser. Summary of the invention

[0005] In view of this, the present invention proposes a high-power fiber green laser that can increase the threshold of stimulated Brillouin scattering effect in optical fiber, improve the peak power of the fiber laser, and simplify the laser frequency doubling optical path structure.

[0006] The present invention provides a high-power fiber green laser, comprising:

[0007] The seed source module is used to provide a seed light source with adjustable pulse width and repetition rate, and to perform phase modulation on the seed light source to broaden the spectrum;

[0008] A first-stage amplification unit is connected to the output optical path of the seed source module and is used to amplify the power of the seed light;

[0009] The secondary amplification unit is connected to the output optical path of the primary amplification unit and is used to amplify the power of the seed light amplified by the primary amplification unit again;

[0010] The third-stage amplification unit is connected to the output optical path of the second-stage amplification unit and is used to perform a third power amplification on the laser output by the second-stage amplification unit;

[0011] The frequency doubling output unit is connected to the output optical path of the three-stage amplification unit, and is used to perform frequency doubling and wavelength selection on the laser of the third power amplification, and output green laser with a specified divergence angle and spot size.

[0012] On the basis of the above technical scheme, preferably, the seed source module includes a distributed feedback laser, a polarization-maintaining fiber, a phase modulator, a radio frequency driver and a first polarization-maintaining optical isolator; the output end of the distributed feedback laser is optically connected to one end of the polarization-maintaining optical fiber, the other end of the polarization-maintaining optical fiber is optically connected to the input end of the phase modulator, the driving end of the phase modulator is signal-connected to the output end of the radio frequency driver, the output end of the phase modulator is optically connected to the input end of the first polarization-maintaining optical isolator, and the output end of the first polarization-maintaining optical isolator serves as the output end of the seed source module to output seed light to the first-stage amplification unit; the radio frequency driver is used to generate a sinusoidal wave signal and apply it to the phase modulator to change the line width of the initial laser; the first polarization-maintaining optical isolator is used to eliminate reflected light in the optical path.

[0013] Preferably, the first-stage amplification unit includes a first polarization-maintaining gain fiber, a first polarization-maintaining pump combiner, a first pump source, and a second polarization-maintaining optical isolator; one end of the first polarization-maintaining gain fiber is connected to the output end optical path of the first polarization-maintaining optical isolator as the input end of the first-stage amplification unit, the other end of the first polarization-maintaining gain fiber is connected to the first end optical path of the first polarization-maintaining pump combiner, the second end of the first polarization-maintaining pump combiner is connected to the output end optical path of the first pump source, the third end of the first polarization-maintaining pump combiner is connected to the input end optical path of the second polarization-maintaining optical isolator, and the output end of the second polarization-maintaining optical isolator is used as the output end of the first-stage amplification unit to output the power-amplified laser; the second polarization-maintaining optical isolator is used to eliminate reflected light in the optical path.

[0014] Further preferably, the secondary amplification unit includes a polarization-maintaining cladding light stripper, a second polarization-maintaining gain fiber, a second polarization-maintaining pump combiner, a second pump source and a third polarization-maintaining optical isolator; the input end of the polarization-maintaining cladding light stripper is optically connected to the output end of the second polarization-maintaining optical isolator as the input end of the secondary amplification unit, the output end of the polarization-maintaining cladding light stripper is optically connected to one end of the second polarization-maintaining gain fiber, the other end of the second polarization-maintaining gain fiber is optically connected to the first end of the second polarization-maintaining pump combiner, the second end of the second polarization-maintaining pump combiner is optically connected to the output end of the second pump source, the third end of the second polarization-maintaining pump combiner is optically connected to the input end of the third polarization-maintaining optical isolator, the output end of the third polarization-maintaining optical isolator is optically connected to the output end of the secondary power amplification as the output end of the secondary amplification unit, and the third polarization-maintaining optical isolator is used to eliminate reflected light in the optical path.

[0015] More preferably, the three-stage amplification unit includes a third polarization-maintaining pump combiner, a third pump source, a fourth pump source, a third polarization-maintaining gain fiber and a C-lens lens; a first end of the third polarization-maintaining pump combiner is optically connected to the output end of the third polarization-maintaining optical isolator, a second end of the third polarization-maintaining pump combiner is optically connected to the output end of the third pump source, a fourth end of the third polarization-maintaining pump combiner is optically connected to the output end of the fourth pump source, and the third polarization-maintaining pump combiner combines the third pump source and the fourth pump source to increase the pump power of the input laser; a third end of the third polarization-maintaining pump combiner is optically connected to one end of the third polarization-maintaining gain fiber, the other end of the third polarization-maintaining gain fiber is fused together with one end of the C-lens lens, and the other end of the C-lens lens serves as the output end of the three-stage amplification unit to collimate and output the laser with increased peak power.

[0016] Still further preferably, the frequency doubling output unit comprises a first dichroic mirror, a second dichroic mirror, a focusing mirror, a frequency doubling crystal, a first light absorption barrel, a third dichroic mirror, a fourth dichroic mirror, a second light absorption barrel and a collimating mirror; the first dichroic mirror is located on the output light path of the three-stage amplification unit, the first light absorption barrel is arranged on the transmission light path of the first dichroic mirror, the second dichroic mirror is arranged on the reflection light path of the first dichroic mirror, the focusing mirror, the frequency doubling crystal and the third dichroic mirror are arranged in sequence on the reflection light path of the second dichroic mirror, and the focusing mirror and the frequency doubling crystal are coaxial with the reflection light path; the second light absorption barrel is arranged on the transmission light path of the third dichroic mirror, the fourth dichroic mirror is arranged on the reflection light path of the third dichroic mirror, the reflection light path of the fourth dichroic mirror is coaxial with the collimating mirror, and the collimating mirror serves as the output end of the frequency doubling output unit to collimate the laser after frequency doubling for output.

[0017] Further preferably, the first polarization-maintaining pump combiner, the second polarization-maintaining pump combiner and the third polarization-maintaining pump combiner are all (2+1)×1 polarization-maintaining pump combiners; wherein the signal input and output fibers of the first polarization-maintaining pump combiner and the second polarization-maintaining pump combiner are both PM 10 / 125μm, and the pump fiber is 105 / 125μm; the signal input fiber of the third polarization-maintaining pump combiner is PM 10 / 125μm, the signal output fiber is PM20 / 250μm, and the pump fiber is 135 / 155μm.

[0018] More preferably, the first polarization-maintaining pump beam combiner and the second polarization-maintaining pump beam combiner adopt a reverse pump beam combining mode, and the third polarization-maintaining pump beam combiner adopts a forward pump beam combining mode.

[0019] More preferably, the first dichroic mirror and the second dichroic mirror have completely the same specifications, transmit 976nm laser and reflect 1064nm laser; the third dichroic mirror and the fourth dichroic mirror have completely the same specifications, transmit 1064nm wavelength laser and reflect 532nm laser.

[0020] More preferably, the focal length of the focusing mirror is 50-100 mm; the length of the double frequency crystal is 15-25 mm; and the focal length of the collimating mirror is 50-300 mm.

[0021] The high-power fiber green laser provided by the present invention has the following advantages compared with the prior art:

[0022] Beneficial effects:

[0023] (1) The seed source module of the present invention is equipped with a radio frequency driving module through a phase modulator. The radio frequency driving module can output a high-speed sinusoidal wave signal, which is applied to the phase modulator to change the line width of the laser signal light. The phase modulator adopts a fast axis passing design, while the laser seed signal light is a slow axis passing design. In this way, when the optical fiber is fused, the axis needs to be fused, which can improve the polarization extinction ratio of the signal light. When the laser frequency is doubled to generate green light, the high polarization state of the signal light can effectively improve the power stability of the laser;

[0024] (2) A three-stage continuous power amplification strategy is adopted, a forward pumping scheme is adopted in the three-stage amplification unit, and a gain fiber collimator composed of a third polarization-maintaining gain fiber and a C-lens lens is used. The gain fiber collimator uses a carbon dioxide welding machine to weld the third polarization-maintaining gain fiber and the C-lens lens together; the third polarization-maintaining gain fiber ensures the polarization state of the output fundamental frequency light, and uses 20 / 250μm or 25 / 250μm fiber to suppress the operation of high-order mode lasers and improve the beam quality; the C-lens is a cylindrical axially transparent plano-convex lens, which can collimate the divergent laser emitted by the optical fiber into a parallel beam;

[0025] (3) The dichroic mirror cooperates with the light absorption bucket to absorb the transmitted light of a specific wavelength, eliminate the component of the corresponding wavelength, and improve the output quality of the green laser after frequency doubling. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying creative work.

[0027] Figure 1 This is a structural block diagram of a high-power fiber green laser of the present invention;

[0028] Figure 2 This is a schematic diagram of the output waveform of a radio frequency driver of a high-power fiber green laser of the present invention;

[0029] Figure 3 The spectrum of the initial laser of a high-power fiber green laser of the present invention;

[0030] Figure 4 The spectrum of the seed light of a high-power fiber green laser of the present invention is broadened by phase modulation.

[0031] Reference numerals: 100, seed source module; 200, primary amplification unit; 300, secondary amplification unit; 400, tertiary amplification unit; 500, frequency doubling output unit;

[0032] 1. Distributed feedback laser; 2. Polarization-maintaining fiber; 3. Phase modulator; 4. RF driver; 5. First polarization-maintaining optical isolator; 6. First polarization-maintaining gain fiber; 7. First polarization-maintaining pump combiner; 8. First pump source; 9. Second polarization-maintaining optical isolator; 10. Polarization-maintaining cladding light stripper; 11. Second polarization-maintaining gain fiber; 12. Second polarization-maintaining pump combiner; 13. Second pump source; 14. Third polarization-maintaining optical isolator; 15. Third polarization-maintaining pump combiner; 16. Third pump source; 17. Fourth pump source; 18. Third polarization-maintaining gain fiber; 19. C-lens; 20. First dichroic mirror; 21. Second dichroic mirror; 22. Focusing mirror; 23. Double frequency crystal; 24. First light absorption barrel; 25. Third dichroic mirror; 26. Fourth dichroic mirror; 27. Second light absorption barrel; 28. Collimating mirror. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions 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 are within the scope of protection of the present invention.

[0034] The existing fiber green lasers have the following problems: 1. They fail to improve the threshold of stimulated Brillouin scattering effect in the fiber. When the fiber fundamental frequency power is amplified, the peak power is limited and the pulse width range only supports less than 2ns.

[0035] 2. The frequency doubling structure is complex. Figure 1 As shown, the present invention provides a high-power fiber green laser, comprising:

[0036] The seed source module 100 is used to provide a seed light source with adjustable pulse width and repetition frequency. The phase modulator is connected to the output optical path of the seed source module to perform phase modulation on the seed light source to broaden the spectrum.

[0037] The first-stage amplification unit 200 is connected to the output optical path of the seed source module 100 and is used to amplify the power of the seed light;

[0038] The secondary amplifying unit 300 is connected to the output optical path of the primary amplifying unit 200, and is used to amplify the power of the seed light amplified by the primary amplifying unit 200 again;

[0039] The third-stage amplification unit 400 is optically connected to the output end of the second-stage amplification unit 300, and is used to perform a third power amplification on the laser output by the second-stage amplification unit 300;

[0040] The frequency doubling output unit 500 is connected to the output optical path of the three-stage amplification unit 400, and is used to perform frequency doubling and wavelength selection on the third power amplified laser, and output green laser with a specified divergence angle and spot size.

[0041] By analyzing the coupling equation of the SBS process, the following expression is obtained: Where P th is the SBS threshold, A eff is the effective mode field area of ​​the optical fiber, ΔV B is the half-maximum width of the laser gain spectrum, i.e., the laser line width; P kis the laser peak power, and L is the length of the laser transmission fiber. To ensure the peak power of laser amplification, the following measures can be adopted: 1. Use optical fibers with larger mode field areas; 2. Phase modulate the seed light to increase the line width of the laser; 3. Use forward amplification integrated devices to shorten the length of the main stage optical fiber. By raising the threshold of Stokes light through the above method, the stimulated Brillouin scattering effect can be effectively suppressed, greatly improving the peak power of the fiber green laser. In actual use, optical fibers with large mode field areas allow more modes of laser transmission, and the output laser beam quality is poor. Therefore, the present invention mainly improves points 2 and 3.

[0042] like Figure 1 Combination Figure 2 As shown, the seed source module 100 includes a distributed feedback laser 1, a polarization-maintaining fiber 2, a phase modulator 3, a radio frequency driver 4 and a first polarization-maintaining optical isolator 5; the output end of the distributed feedback laser 1 is optically connected to one end of the polarization-maintaining optical fiber 2, the other end of the polarization-maintaining optical fiber 2 is optically connected to the input end of the phase modulator 3, the driving end of the phase modulator 3 is signal-connected to the output end of the radio frequency driver 4, the output end of the phase modulator 3 is optically connected to the input end of the first polarization-maintaining optical isolator 5, and the output end of the first polarization-maintaining optical isolator 5 serves as the output end of the seed source module 100 to output seed light to the first-stage amplification unit 200; the radio frequency driver 4 is used to generate a sinusoidal wave signal and apply it to the phase modulator 3 to change the line width of the initial laser; the first polarization-maintaining optical isolator 5 is used to eliminate reflected light in the optical path.

[0043] A high-speed phase modulator is introduced in the seed source module 100. The bandwidth of the phase modulator is in the order of hundreds of MHz-GHz, which can respond to high-speed signal modulation and effectively broaden the initial laser line width. Specifically, the phase modulator is equipped with a radio frequency driving module, such as Figure 2 As shown, the RF driver module can output a high-speed sinusoidal signal, which is applied to the phase modulator to change the line width of the laser signal light. The RF driver module uses a TTL clock signal from the control circuit as a switch to control the phase modulator. In order to better dissipate the heat of the RF driver 4, the RF driver 4 is fixed on the laser water cooling plate using an L-shaped adapter. A thermal conductive silicone pad needs to be placed under the RF driver 4, which can be insulated from the laser packaging shell and increase the contact area to improve the heat dissipation capacity. The distributed feedback laser 1, namely the DFB-A laser, is mainly based on semiconductor materials, including gallium antimonide (GaSb), gallium arsenide (GaAs), indium phosphide (InP), zinc sulfide (ZnS), etc. The biggest feature of the distributed feedback laser 1 is that it has very good monochromaticity, that is, spectral purity. Its line width can generally be within 1MHz, and it has a very high side mode suppression ratio. Figure 3 and Figure 4They are the spectra of the initial laser before and after modulation, respectively. The horizontal axis represents the wavelength in nm, and the vertical axis represents the relative light intensity of the corresponding wavelength in dBm. Figure 3 and Figure 4 The λc in the spectrum is 1063.6429nm, Figure 3 The width of the dashed box at the central wavelength of the spectrum represents the line width △λ of the laser before phase modulation, which is 0.2153nm. Figure 4 The width of the dotted box at the center wavelength of the spectrum represents the line width △λ of the laser after phase modulation. At this time, △λ is 0.2590nm, which is 1.2 times that before modulation. That is, the line width of the initial laser is increased by 20% through modulation, achieving the adjustment of ΔV B effect.

[0044] In this embodiment, the distributed feedback laser 1 has an output central wavelength of 1064±2nm, a 3dB bandwidth of 0.05±0.02nm, and an average power of 0.1-10mW; the polarization-maintaining optical fiber 2 is PM980 optical fiber; the insertion loss of the phase modulator 3 is less than 3dB, and the bandwidth is 0.1-10GHz; the bandwidth range of the RF driver 4 is 0.1-10GHz, and the peak-to-peak voltage range is ±12V to ±25V; the average power of the first polarization-maintaining optical isolator 5 is less than 300mW, the input end uses PM980 optical fiber, and the output end uses PM10 / 125μm optical fiber.

[0045] like Figure 1 As shown, the primary amplification unit 200 includes a first polarization-maintaining gain fiber 6, a first polarization-maintaining pump combiner 7, a first pump source 8, and a second polarization-maintaining optical isolator 9; one end of the first polarization-maintaining gain fiber 6 is optically connected to the output end of the first polarization-maintaining optical isolator 5 as the input end of the primary amplification unit 200, the other end of the first polarization-maintaining gain fiber 6 is optically connected to the first end of the first polarization-maintaining pump combiner 7, the second end of the first polarization-maintaining pump combiner 7 is optically connected to the output end of the first pump source 8, the third end of the first polarization-maintaining pump combiner 7 is optically connected to the input end of the second polarization-maintaining optical isolator 9, and the output end of the second polarization-maintaining optical isolator 9 is used as the output end of the primary amplification unit 200 to output the laser after power amplification; the second polarization-maintaining optical isolator 9 is used to eliminate reflected light in the optical path.

[0046] In this embodiment, the first polarization-maintaining gain fiber 6 is a PM10 / 125μm polarization-maintaining gain fiber with a length of 2 meters and an absorption coefficient of 0.6dB / m@915nm; the first polarization-maintaining pump combiner 7 is a (2+1)×1 reverse pump combiner. Among the parameters of the pump combiner, the parameter before the plus sign in the brackets indicates the number of pump sources that can be combined, the parameter after the plus sign in the brackets indicates the number of paths of the combined signal energy, and the parameter after the multiplication sign indicates that the combined optical signal is output through one channel after the combination. The first end of the polarization-maintaining pump combiner is the input end, the third end is the output end, and the second end and the fourth end are the pump source input ends, respectively, the same below; the first pump source 8 is a 10W 915nm pump source; the average power of the second polarization-maintaining optical isolator 9 is less than 2W, and the input and output optical fibers are both PM10 / 125μm polarization-maintaining fibers, and the slow axis passes through. The signal input and output optical fibers of the first polarization-maintaining pump combiner 7 are both PM 10 / 125 μm, and the pump optical fiber is 105 / 125 μm.

[0047] The secondary amplification unit 300 includes a polarization-maintaining cladding light stripper 10, a second polarization-maintaining gain fiber 11, a second polarization-maintaining pump combiner 12, a second pump source 13 and a third polarization-maintaining optical isolator 14; the input end of the polarization-maintaining cladding light stripper 10 is optically connected to the output end of the second polarization-maintaining optical isolator 9 as the input end of the secondary amplification unit 300, the output end of the polarization-maintaining cladding light stripper 10 is optically connected to one end of the second polarization-maintaining gain fiber 11, the other end of the second polarization-maintaining gain fiber 11 is optically connected to the first end of the second polarization-maintaining pump combiner 12, the second end of the second polarization-maintaining pump combiner 12 is optically connected to the output end of the second pump source 13, the third end of the second polarization-maintaining pump combiner 12 is optically connected to the input end of the third polarization-maintaining optical isolator 14, the output end of the third polarization-maintaining optical isolator 14 is optically connected to the output end of the secondary amplification unit 300 to output the laser after secondary power amplification, and the third polarization-maintaining optical isolator 14 is used to eliminate reflected light in the optical path.

[0048] In this embodiment, the second polarization-maintaining gain fiber 11 is a PM10 / 125μm polarization-maintaining gain fiber, 3 meters in length, and has an absorption coefficient of 2.0dB / m@976nm; the second polarization-maintaining pump combiner 12 is a (2+1)×1 reverse pump combiner; the second pump source 13 is a 27W 976nm pump source; the average power of the third polarization-maintaining optical isolator 14 is less than 10W, and the input and output fibers are both PM10 / 125μm polarization-maintaining gain fibers, through which the slow axis passes. The signal input and output fibers of the second polarization-maintaining pump combiner 12 are both PM 10 / 125μm, and the pump fiber is 105 / 125μm.

[0049] The three-stage amplification unit 400 includes a third polarization-maintaining pump combiner 15, a third pump source 16, a fourth pump source 17, a third polarization-maintaining gain fiber 18 and a C-lens lens 19; a first end of the third polarization-maintaining pump combiner 15 is optically connected to the output end of the third polarization-maintaining optical isolator 14, a second end of the third polarization-maintaining pump combiner 15 is optically connected to the output end of the third pump source 16, a fourth end of the third polarization-maintaining pump combiner 15 is optically connected to the output end of the fourth pump source 17, and the third polarization-maintaining pump combiner 15 combines the third pump source 16 and the fourth pump source 17 to increase the pump power of the input laser; a third end of the third polarization-maintaining pump combiner 15 is optically connected to one end of the third polarization-maintaining gain fiber 18, the other end of the third polarization-maintaining gain fiber 18 is fused to one end of the C-lens lens 19, and the other end of the C-lens lens 19 is used as the output end of the three-stage amplification unit 400 to collimate the laser after providing the peak power.

[0050] In this embodiment, the third polarization-maintaining pump combiner 15 is a (2+1)×1 forward pump combiner, the signal input fiber is PM 10 / 125μm, the signal output fiber is PM20 / 250μm, and the pump fiber is 135 / 155μm; the third pump source 16 and the fourth pump source 17 are both 976nm pump sources, and the pump power is selected from 80-240W according to product requirements; the third polarization-maintaining gain fiber 18 is PM20 / 250μm or PM25 / 250μm polarization-maintaining gain fiber with an absorption coefficient of 5dB / m@976nm; the C-lens 19 collimates the third power-amplified laser to 1mm for output. The three-stage amplification unit 400 adopts a forward pumping solution, and uses a gain fiber collimator composed of a third polarization-maintaining gain fiber 18 and a C-lens lens 19, that is, a carbon dioxide fusion machine is used to fuse the third polarization-maintaining gain fiber 18 and the C-lens lens 19 together. The third polarization-maintaining gain fiber 18 is a polarization-maintaining fiber to ensure the polarization state of the output fundamental frequency light, which can suppress the operation of high-order mode lasers and improve the beam quality. The C-lens lens 19 is a cylindrical axially transparent plano-convex lens, which can collimate the divergent laser emitted by the optical fiber into a parallel beam. Here, the third polarization-maintaining gain fiber 18 and the C-lens lens 19 are fused together to form an integral integrated molding, which has the benefit of shortening the length of the laser transmission optical fiber and achieving the effect of adjusting the length L of the laser transmission optical fiber.

[0051] The frequency doubling output unit 500 includes a first dichroic mirror 20, a second dichroic mirror 21, a focusing mirror 22, a double frequency crystal 23, a first light absorption barrel 24, a third dichroic mirror 25, a fourth dichroic mirror 26, a second light absorption barrel 27 and a collimating mirror 28; the first dichroic mirror 20 is located on the output light path of the three-stage amplification unit 400, the first light absorption barrel 24 is arranged on the transmission light path of the first dichroic mirror 20, the second dichroic mirror 21 is arranged on the reflection light path of the first dichroic mirror 20, and the reflection light path of the second dichroic mirror 21 is connected to the focusing mirror 22. The input optical path is connected, the output end of the focusing mirror 22 is connected to the input optical path of the double frequency crystal 23, a third dichroic mirror 25 is arranged on the optical path of the output end of the double frequency crystal 23, a second light absorption barrel 27 is arranged on the transmission optical path of the third dichroic mirror 25, a fourth dichroic mirror 26 is arranged on the reflection optical path of the third dichroic mirror 25, the output optical path of the fourth dichroic mirror 26 is connected to the input optical path of the collimating mirror 28, and the output end of the collimating mirror 28 serves as the output end of the frequency doubling output unit 500 to collimate the laser to the required spot size for output.

[0052] In this embodiment, the first dichroic mirror 20 and the second dichroic mirror 21 have the same specifications, transmit 976nm laser and reflect 1064nm laser; the third dichroic mirror 25 and the fourth dichroic mirror 26 have the same specifications, transmit 1064nm wavelength laser and reflect 532nm laser; the focal length of the focusing mirror 22 is 50-100mm; the length of the double frequency crystal 23 is 15-25mm, and the material is lithium triborate; the focal length of the collimating mirror 28 is 50-300mm. The first light absorption barrel 24 absorbs the residual 976nm laser, and the second light absorption barrel 27 absorbs the 1064nm laser.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-power fiber green laser, characterized in that: include: A seed source module (100) is used to provide a seed light source with adjustable pulse width and repetition rate, and to perform phase modulation on the seed light source to broaden the spectrum; A first-stage amplification unit (200) is connected to the output optical path of the seed source module (100) and is used to amplify the power of the seed light; A secondary amplification unit (300) is connected to the output end optical path of the primary amplification unit (200) and is used to re-amplify the power of the seed light amplified by the primary amplification unit (200); A third-stage amplification unit (400) is optically connected to the output end of the second-stage amplification unit (300) and is used to perform a third power amplification on the laser output by the second-stage amplification unit (300); The frequency doubling output unit (500) is connected to the output end optical path of the three-stage amplification unit (400) and is used to perform frequency doubling and wavelength selection on the third power amplified laser and output green laser with a specified divergence angle and spot size.

2. A high-power fiber green laser according to claim 1, characterized in that: The seed source module (100) comprises a distributed feedback laser (1), a polarization-maintaining optical fiber (2), a phase modulator (3), a radio frequency driver (4) and a first polarization-maintaining optical isolator (5); the output end of the distributed feedback laser (1) is optically connected to one end of the polarization-maintaining optical fiber (2), the other end of the polarization-maintaining optical fiber (2) is optically connected to the input end of the phase modulator (3), the driving end of the phase modulator (3) is signal-connected to the output end of the radio frequency driver (4), the output end of the phase modulator (3) is optically connected to the input end of the first polarization-maintaining optical isolator (5), and the output end of the first polarization-maintaining optical isolator (5) serves as the output end of the seed source module (100) to output seed light to the primary amplification unit (200); The radio frequency driver (4) is used to generate a sinusoidal wave signal and apply it to the phase modulator (3) to change the line width of the initial laser; the first polarization-maintaining optical isolator (5) is used to eliminate reflected light in the optical path.

3. A high-power fiber green laser according to claim 2, characterized in that: The first-stage amplification unit (200) comprises a first polarization-maintaining gain optical fiber (6), a first polarization-maintaining pump combiner (7), a first pump source (8), and a second polarization-maintaining optical isolator (9); one end of the first polarization-maintaining gain optical fiber (6) is optically connected to the output end of the first polarization-maintaining optical isolator (5) as the input end of the first-stage amplification unit (200); the other end of the first polarization-maintaining gain optical fiber (6) is optically connected to the first end of the first polarization-maintaining pump combiner (7); the second end of the first polarization-maintaining pump combiner (7) is optically connected to the output end of the first pump source (8); the third end of the first polarization-maintaining pump combiner (7) is optically connected to the input end of the second polarization-maintaining optical isolator (9); the output end of the second polarization-maintaining optical isolator (9) is optically connected to the output end of the first-stage amplification unit (200) to output power-amplified laser light; and the second polarization-maintaining optical isolator (9) is used to eliminate reflected light in the optical path.

4. A high-power fiber green laser according to claim 3, characterized in that: The secondary amplification unit (300) comprises a polarization-maintaining cladding light stripper (10), a second polarization-maintaining gain optical fiber (11), a second polarization-maintaining pump combiner (12), a second pump source (13) and a third polarization-maintaining optical isolator (14); the input end of the polarization-maintaining cladding light stripper (10) is optically connected to the output end of the second polarization-maintaining optical isolator (9) as the input end of the secondary amplification unit (300); the output end of the polarization-maintaining cladding light stripper (10) is optically connected to one end of the second polarization-maintaining gain optical fiber (11); the second polarization-maintaining gain optical fiber (11) is optically connected to the output end of the second polarization-maintaining gain optical fiber (9). The other end of the fiber (11) is optically connected to the first end of the second polarization-maintaining pump beam combiner (12), the second end of the second polarization-maintaining pump beam combiner (12) is optically connected to the output end of the second pump source (13), the third end of the second polarization-maintaining pump beam combiner (12) is optically connected to the input end of the third polarization-maintaining optical isolator (14), the output end of the third polarization-maintaining optical isolator (14) serves as the output end of the secondary amplification unit (300) to output laser light after secondary power amplification, and the third polarization-maintaining optical isolator (14) is used to eliminate reflected light in the optical path.

5. A high-power fiber green laser according to claim 4, characterized in that: The three-stage amplification unit (400) comprises a third polarization-maintaining pump combiner (15), a third pump source (16), a fourth pump source (17), a third polarization-maintaining gain optical fiber (18) and a C-lens (19); a first end of the third polarization-maintaining pump combiner (15) is optically connected to the output end of the third polarization-maintaining optical isolator (14), a second end of the third polarization-maintaining pump combiner (15) is optically connected to the output end of the third pump source (16), and a fourth end of the third polarization-maintaining pump combiner (15) is optically connected to the output end of the fourth pump source (17). The third polarization-maintaining pump combiner (15) is connected to an optical path of an end of a third polarization-maintaining gain optical fiber (18), and the third polarization-maintaining pump combiner (15) is combined with a third pump source (16) and a fourth pump source (17) to increase the pump power of the input laser; the third end of the third polarization-maintaining pump combiner (15) is connected to an optical path of one end of a third polarization-maintaining gain optical fiber (18), and the other end of the third polarization-maintaining gain optical fiber (18) is fused together with one end of a C-lens lens (19), and the other end of the C-lens lens (19) serves as the output end of the three-stage amplification unit (400) to collimate and output the laser with increased peak power.

6. A high-power fiber green laser according to claim 5, characterized in that: The frequency doubling output unit (500) comprises a first dichroic mirror (20), a second dichroic mirror (21), a focusing mirror (22), a frequency doubling crystal (23), a first light absorption barrel (24), a third dichroic mirror (25), a fourth dichroic mirror (26), a second light absorption barrel (27) and a collimating mirror (28); the first dichroic mirror (20) is located on the output light path of the three-stage amplification unit (400), the first light absorption barrel (24) is arranged on the transmission light path of the first dichroic mirror (20), the second dichroic mirror (21) is arranged on the reflection light path of the first dichroic mirror (20), and the third dichroic mirror (25) is arranged on the fourth dichroic mirror (26). A focusing mirror (22), a frequency doubling crystal (23), and a third dichroic mirror (25) are sequentially placed on the reflected light path of the second dichroic mirror (21), and the focusing mirror (22) and the frequency doubling crystal (23) are coaxial with the reflected light path; a second light absorption barrel (27) is arranged on the transmitted light path of the third dichroic mirror (25), and a fourth dichroic mirror (26) is arranged on the reflected light path of the third dichroic mirror (25), and the reflected light path of the fourth dichroic mirror (26) is coaxial with a collimating mirror (28), and the collimating mirror (28) serves as the output end of the frequency doubling output unit (500) to collimate and output the frequency-doubled laser.

7. A high-power fiber green laser according to claim 6, characterized in that: The first polarization-maintaining pump combiner (7), the second polarization-maintaining pump combiner (12) and the third polarization-maintaining pump combiner (15) are all (2+1)×1 polarization-maintaining pump combiners; wherein the signal input and output optical fibers of the first polarization-maintaining pump combiner (7) and the second polarization-maintaining pump combiner (12) are both PM 10 / 125 μm, and the pump optical fiber is 105 / 125 μm; the signal input optical fiber of the third polarization-maintaining pump combiner (15) is PM 10 / 125 μm, the signal output optical fiber is PM20 / 250 μm, and the pump optical fiber is 135 / 155 μm.

8. A high-power fiber green laser according to claim 6, characterized in that: The first polarization-maintaining pump beam combiner (7) and the second polarization-maintaining pump beam combiner (12) adopt a reverse pump beam combining mode, and the third polarization-maintaining pump beam combiner (15) adopts a forward pump beam combining mode.

9. A high-power fiber green laser according to claim 6, characterized in that: The first dichroic mirror (20) and the second dichroic mirror (21) have completely the same specifications, transmit 976nm laser light and reflect 1064nm laser light; the third dichroic mirror (25) and the fourth dichroic mirror (26) have completely the same specifications, transmit 1064nm wavelength laser light and reflect 532nm laser light.

10. A high-power fiber green laser according to claim 6, characterized in that: The focal length of the focusing mirror (22) is 50-100 mm; the length of the double frequency crystal (23) is 15-25 mm; and the focal length of the collimating mirror (28) is 50-300 mm.

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