A high-power green fiber laser

Abstract

The application provides a high-power optical fiber green laser, and belongs to the technical field of optical fiber lasers; specifically comprises a seed source module, which is used for providing a seed light source with adjustable pulse width and frequency, and performing phase modulation on the seed light source to broaden the spectrum; a first amplification unit is connected with an output end optical path of the seed source module and is used for performing power amplification on the seed light; a second amplification unit is connected with an output end optical path of the first amplification unit and is used for performing power amplification on the signal light again; a third amplification unit is connected with an output end optical path of the second amplification unit and is used for performing third power amplification on the laser; a frequency doubling output unit is connected with an output end optical path of the third amplification unit and is used for performing frequency doubling on the laser amplified for the third time, so as to output green laser with a specified divergence angle and spot size. The application improves the SBS threshold from two aspects of phase modulation and shortening the length of the optical fiber, so that the peak power of the optical fiber green laser is higher.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fiber lasers, in particular to a high-power fiber green laser. BACKGROUND

[0002] Green laser has the characteristics of high single photon energy, good beam quality, strong material effect, etc., and is widely used in industrial precision machining, material surface treatment, scientific research and military industry, biological medicine, etc. Especially with the rapid development of semiconductor, 3C and new energy industry, green laser performs excellently in industrial metal material marking, copper material cutting and scribing application. At present, the products on the market are mainly solid green lasers, which use ytterbium-doped and neodymium-doped crystals as laser gain medium, and through the technology route of intracavity or extracavity frequency doubling, it is easy to realize high peak value and large energy nanosecond green laser output, and the structure is simple and compact, but the long-term working stability is poor, and the pulse width, repetition frequency and other parameters cannot be flexibly adjusted, and the average power is low. The fiber green laser adopts the technical route of combining fiber fundamental frequency with solid frequency doubling, the polarization maintaining fiber is used for amplification to ensure high polarization state of the fundamental frequency, thereby ensuring the frequency doubling efficiency; the fiber fundamental frequency adopts MOPA structure, which can realize high-precision seed waveform editing, and the output seed signal is controlled by software, which has the advantages of adjustable repetition frequency and pulse width, high average output power and good stability; the fundamental frequency light amplified by the fiber is spatially collimated, and the nonlinear crystal is used for frequency doubling, which has the advantages of simple structure and excellent beam quality, and greatly improves the industrial processing efficiency.

[0003] Chinese utility model patent CN219801481U discloses a 150ps-2ns all-fiber green and ultraviolet laser modulated by two Mach-Zehnder intensity modulators in cascade, which improves the average power of the green laser to some extent. However, there are still some problems: 1. The threshold of stimulated Brillouin scattering effect in the fiber cannot be improved, and the peak power is limited when the fiber fundamental frequency is amplified, and the pulse width range only supports below 2ns. 2. The frequency doubling structure is complex, and the frequency doubling efficiency is about 65% under the design of multiple frequency doubling groups.

[0004] Therefore, it is necessary to provide a high-power fiber green laser, which improves the threshold of stimulated Brillouin scattering by analyzing the threshold condition of stimulated Brillouin scattering, and improves the peak power of the fiber green laser by improving the laser linewidth through phase modulation of the seed light and shortening the length of the main amplifier stage. SUMMARY

[0005] Therefore, it is necessary to provide a high-power fiber green laser, which improves the threshold of stimulated Brillouin scattering by analyzing the threshold condition of stimulated Brillouin scattering, and improves the peak power of the fiber green laser by improving the laser linewidth through phase modulation of the seed light and shortening the length of the main amplifier stage.

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

[0007] A seed source module is configured to provide a seed light source with adjustable pulse width and repetition frequency, and to perform phase modulation on the seed light source to broaden the spectrum.

[0008] A first amplification unit is connected to the output end of the seed source module in an optical path, and is configured to perform power amplification on the seed light.

[0009] A second amplification unit is connected to the output end of the first amplification unit in an optical path, and is configured to perform power amplification again on the seed light amplified by the first amplification unit.

[0010] A third amplification unit is connected to the output end of the second amplification unit in an optical path, and is configured to perform third power amplification on the laser output by the second amplification unit.

[0011] A frequency doubling output unit is connected to the output end of the third amplification unit in an optical path, and is configured to perform frequency doubling and wavelength selection on the laser subjected to 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 comprises a distributed feedback laser, a polarization maintaining optical fiber, a phase modulator, a radio frequency driver and a first polarization maintaining optical isolator; the output end of the distributed feedback laser is connected to one end of the polarization maintaining optical fiber in an optical path, the other end of the polarization maintaining optical fiber is connected to the input end of the phase modulator in an optical path, the driving end of the phase modulator is connected to the output end of the radio frequency driver in a signal connection, the output end of the phase modulator is connected to the input end of the first polarization maintaining optical isolator in an optical path, and the output end of the first polarization maintaining optical isolator serves as the output end of the seed source module and outputs the seed light to the first amplification unit; the radio frequency driver is configured to generate a sinusoidal signal and apply the sinusoidal signal to the phase modulator to change the initial laser line width; and the first polarization maintaining optical isolator is configured to eliminate reflected light in the optical path.

[0013] Preferably, the first amplification unit comprises a first polarization maintaining gain optical 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 optical fiber serves as the input end of the first amplification unit and is connected to the output end of the first polarization maintaining optical isolator in an optical path, the other end of the first polarization maintaining gain optical fiber is connected to the first end of the first polarization maintaining pump combiner in an optical path, the second end of the first polarization maintaining pump combiner is connected to the output end of the first pump source in an optical path, the third end of the first polarization maintaining pump combiner is connected to the input end of the second polarization maintaining optical isolator in an optical path, and the output end of the second polarization maintaining optical isolator serves as the output end of the first amplification unit and outputs the laser subjected to power amplification; and the second polarization maintaining optical isolator is configured to eliminate reflected light in the optical path.

[0014] Further preferably, the secondary amplification unit comprises 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 connected in optical path with 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 connected in optical path with one end of the second polarization maintaining gain fiber, the other end of the second polarization maintaining gain fiber is connected in optical path with the first end of the second polarization maintaining pump combiner, the second end of the second polarization maintaining pump combiner is connected in optical path with the output end of the second pump source, the third end of the second polarization maintaining pump combiner is connected in optical path with the input end of the third polarization maintaining optical isolator, and the output end of the third polarization maintaining optical isolator outputs the laser after secondary power amplification as the output end of the secondary amplification unit, and the third polarization maintaining optical isolator is used for eliminating reflected light in the optical path.

[0015] Further preferably, the tertiary amplification unit comprises a third polarization maintaining pump combiner, a third pump source, a fourth pump source, a third polarization maintaining gain fiber and a C-lens; the first end of the third polarization maintaining pump combiner is connected in optical path with the output end of the third polarization maintaining optical isolator, the second end of the third polarization maintaining pump combiner is connected in optical path with the output end of the third pump source, the fourth end of the third polarization maintaining pump combiner is connected in optical path with the output end of the fourth pump source, 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; the third end of the third polarization maintaining pump combiner is connected in optical path with 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, and the other end of the C-lens is the output end of the tertiary amplification unit to collimate and output the laser with increased peak power.

[0016] Further preferably, the frequency doubling output unit comprises a first dichroic mirror, a second dichroic mirror, a focusing lens, a second doubling crystal, a first light absorption barrel, a third dichroic mirror, a fourth dichroic mirror, a second light absorption barrel and a collimating lens; the first dichroic mirror is located on the output optical path of the tertiary amplification unit, the first light absorption barrel is arranged on the transmission optical path of the first dichroic mirror, the second dichroic mirror is arranged on the reflection optical path of the first dichroic mirror, the focusing lens, the second doubling crystal and the third dichroic mirror are sequentially arranged on the reflection optical path of the second dichroic mirror, and the focusing lens and the second doubling crystal are coaxial with the reflection optical path; the second light absorption barrel is arranged on the transmission optical path of the third dichroic mirror, the fourth dichroic mirror is arranged on the reflection optical path of the third dichroic mirror, the reflection optical path of the fourth dichroic mirror is coaxial with the collimating lens, and the collimating lens is the output end of the frequency doubling output unit to collimate and output the frequency-doubled laser.

[0017] Further preferably, the first, second and third polarization-maintaining pump combiners are all (2+1) x 1 polarization-maintaining pump combiners; the signal input and output fibers of the first and second polarization-maintaining pump combiners are PM 10 / 125 mu m, the pump fiber is 105 / 125 mu m, the signal input fiber of the third polarization-maintaining pump combiner is PM 10 / 125 mu m, the signal output fiber is PM 20 / 250 mu m, and the pump fiber is 135 / 155 mu m.

[0018] Further preferably, the first and second polarization-maintaining pump combiners adopt a backward pump combining mode, and the third polarization-maintaining pump combiner adopts a forward pump combining mode.

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

[0020] Further preferably, the focal length of the focusing mirror is 50-100 mm, the length of the second-harmonic generation crystal is 15-25 mm, and the focal length of the collimating mirror is 50-300 mm.

[0021] The high-power optical fiber green laser provided by the application has the following advantages over the prior art.

[0022] Advantages:

[0023] (1) The seed source module of the application is equipped with a radio frequency driving module, which can output a high-speed sinusoidal signal and apply it to the phase modulator to change the linewidth of the laser signal light. The phase modulator adopts a fast-axis passing design, while the laser seed signal light passes through the slow axis. Therefore, the shaft fusion splicing is required when the optical fiber is spliced, which can improve the polarization extinction ratio of the signal light. When the green light is generated by laser frequency doubling, the high polarization state of the signal light can effectively improve the power stability of the laser.

[0024] (2) The three-stage continuous power amplification strategy is adopted, and the forward pumping scheme is adopted in the three-stage amplification unit. The gain fiber collimator is composed of a third polarization-maintaining gain fiber and a C-lens lens. The third polarization-maintaining gain fiber and the C-lens lens are fused together by a carbon dioxide fusion splicer. The third polarization-maintaining gain fiber ensures the polarization state of the output fundamental frequency light, adopts 20 / 250 mu m or 25 / 250 mu m optical fiber, can suppress high-order mode laser operation, and improve the beam quality. The C-lens lens is a cylindrical axially passing convex lens, which can collimate the divergent laser emitted by the optical fiber into a parallel light beam.

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

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0027] Figure 1 The structural block diagram of the high-power optical fiber green laser of the present application;

[0028] Figure 2 The output waveform schematic diagram of the radio frequency driver of the high-power optical fiber green laser of the present application;

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

[0030] Figure 4 The spectrum of the seed light after phase modulation and broadening of the high-power optical fiber green laser of the present application.

[0031] Reference signs: 100, seed source module; 200, first amplification unit; 300, second amplification unit; 400, third amplification unit; 500, frequency doubling output unit;

[0032] 1, distributed feedback laser; 2, polarization maintaining optical fiber; 3, phase modulator; 4, radio frequency driver; 5, first polarization maintaining optical isolator; 6, first polarization maintaining gain optical 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 optical 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 optical fiber; 19, C-lens lens; 20, first dichroic mirror; 21, second dichroic mirror; 22, focusing lens; 23, second frequency doubling crystal; 24, first light absorption barrel; 25, third dichroic mirror; 26, fourth dichroic mirror; 27, second light absorption barrel; 28, collimating lens. 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 embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Existing fiber green lasers have the following limitations: 1. They fail to increase the threshold of stimulated Brillouin scattering in optical fibers. 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. In view of this, if 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 and is used 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 optically connected to the output end of the primary amplifying unit 200 and is used to further power-amplify the seed light amplified by the primary amplifying unit 200.

[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 optically connected to the output end of the three-stage amplification unit 400 and is used to perform frequency doubling and wavelength selection on the laser light after the third power amplification and output a green laser light 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 full width at half maximum of the laser gain spectrum, i.e. the laser line width; P kFor the peak power of the laser, L is the length of the laser transmission fiber. In order to ensure the peak power of the laser amplification, the following measures can be taken: 1. A fiber with a larger mode field area can be used; 2. The linewidth of the laser can be increased by phase modulation of the seed light; 3. A forward amplification integrated device is used to shorten the length of the main amplification stage fiber. By increasing the threshold of the Stokes light through the above methods, the stimulated Brillouin scattering effect can be effectively suppressed, and the peak power of the fiber green laser can be greatly improved. In actual use, the fiber with a large mode field area can allow more modes of laser transmission, and the output laser beam quality is poor, so the present application mainly improves from the second point and the third point.

[0042] As shown in Figure 1 In combination Figure 2 As shown in the figure, 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 with one end of the polarization maintaining fiber 2, the other end of the polarization maintaining fiber 2 is optically connected with the input end of the phase modulator 3, the driving end of the phase modulator 3 is signal connected with the output end of the radio frequency driver 4, the output end of the phase modulator 3 is optically connected with the input end of the first polarization maintaining optical isolator 5, and the output end of the first polarization maintaining optical isolator 5 is as the output end of the seed source module 100 and outputs the seed light to the first amplification unit 200. The radio frequency driver 4 is used to generate a sinusoidal signal and apply it to the phase modulator 3 to change the linewidth of the initial laser. The first polarization maintaining optical isolator 5 is used to eliminate the reflected light in the optical path.

[0043] A high-speed phase modulator is introduced in the seed source module 100, and 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 linewidth of the initial laser. Specifically, the phase modulator is equipped with a radio frequency driving module, as shown in Figure 2 The radio frequency driving module can output a high-speed sinusoidal signal and apply it to the phase modulator to change the linewidth of the laser signal light. The radio frequency driving module is switched by the TTL clock signal issued by the control circuit, and then controls the operation of the phase modulator. In order to better dissipate heat from the radio frequency driver 4, the radio frequency driver 4 is fixed on the laser water cooling plate by an L-shaped adapter. A heat-conducting silicone pad is placed under the radio frequency driver 4, which can not only be insulated from the packaging shell of the laser, but also increase the contact area and improve the heat dissipation capacity. The distributed feedback laser 1, i.e. DFB-A laser, is mainly a semiconductor material medium, including gallium antimonide (GaSb), gallium arsenide (GaAs), indium phosphide (InP), zinc sulfide (ZnS) and the like. The maximum feature of the distributed feedback laser 1 is that it has very good monochromaticity, i.e. spectral purity, and its linewidth can generally be within 1MHz, and it also has very high side mode suppression ratio. Figure 3 and Figure 4The spectra of the initial laser before and after modulation, respectively, wherein the horizontal axis represents wavelength in nm, and the vertical axis represents the relative light intensity of the corresponding wavelength in dBm. Figure 3 and Figure 4 The center wavelength λc of the spectrum is 1063.6429 nm, Figure 3 The width of the dashed box at the center wavelength of the spectrum represents the line width Δλ of the laser before phase modulation, wherein Δλ is 0.2153 nm. Figure 4 The width of the dashed box at the center wavelength of the spectrum represents the line width Δλ of the laser after phase modulation, wherein Δλ is 0.2590 nm, which is 1.2 times of the line width before modulation, i.e. the line width of the initial laser is increased by 20% through modulation, achieving the effect of adjusting ΔV B .

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

[0045] As shown in Figure 1 , the first-stage amplification unit 200 includes 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, and the output end of the second polarization maintaining optical isolator 9 outputs the power-amplified laser as the output end of the first-stage amplification unit 200; the second polarization maintaining optical isolator 9 is used to eliminate reflected light in the optical path.

[0046] In the embodiment, the first polarization maintaining gain optical fiber 6 is a PM10 / 125 μm polarization maintaining gain optical fiber, with a length of 2 meters and an absorption coefficient of 0.6 dB / m@915 nm; the first polarization maintaining pump combiner 7 is a (2+1)×1 backward pump combiner, wherein the parameter before the plus sign in the parameter of the pump combiner represents the number of pump sources that can be combined, the parameter after the plus sign in the parameter represents the number of signal energy channels that are combined, and the parameter after the multiplication sign represents the output of the combined optical signal through one channel after combination; the first end of the backward pump combiner is an input end, the third end is an output end, and the second end and the fourth end are pump source input ends, which are the same below; the first pump source 8 is a 10W 915 nm pump source; the average power of the second polarization maintaining optical isolator 9 is <2W, and the input and output optical fibers are both PM10 / 125 μm polarization maintaining optical fibers with slow axis passing.

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

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

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

[0050] In the embodiment, the third polarization-maintaining pump combiner 15 is a (2+1) x 1 forward pump combiner, the signal input fiber is a PM 10 / 125 μm, the signal output fiber is a PM 20 / 250 μm, and the pump fiber is a 135 / 155 μm; the third pump source 16 and the fourth pump source 17 are both 976 nm pump sources, and the pump power is selected to be 80-240 W according to product requirements; the third polarization-maintaining gain fiber 18 is a PM 20 / 250 μm or PM 25 / 250 μm polarization-maintaining gain fiber with an absorption coefficient of 5 dB / m @ 976 nm; and the C-lens lens 19 collimates the laser after the third-stage power amplification to 1 mm output. The third-stage amplification unit 400 adopts a forward pumping scheme, uses a gain fiber collimator composed of the third polarization-maintaining gain fiber 18 and the C-lens lens 19, that is, the third polarization-maintaining gain fiber 18 and the C-lens lens 19 are fused together by using a carbon dioxide fusion machine, the third polarization-maintaining gain fiber 18 is a polarization-maintaining fiber to ensure the polarization state of the output fundamental frequency light, suppress the operation of high-order mode laser, and improve the beam quality, and the C-lens lens 19 is a cylindrical axially transmissive plano-convex lens which can collimate the divergent laser emitted by the fiber into a parallel light beam. The third polarization-maintaining gain fiber 18 and the C-lens lens 19 are fused together to form an integrated and integral molding, which can shorten the length of the laser transmission fiber and achieve the effect of adjusting the length L of the laser transmission fiber.

[0051] The frequency doubling output unit 500 comprises a first dichroic mirror 20, a second dichroic mirror 21, a focusing mirror 22, a second-harmonic crystal 23, a first light absorption bucket 24, a third dichroic mirror 25, a fourth dichroic mirror 26, a second light absorption bucket 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 bucket 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, the reflection light path of the second dichroic mirror 21 is connected with the input end light path of the focusing mirror 22, the output end of the focusing mirror 22 is connected with the input end light path of the second-harmonic crystal 23, the third dichroic mirror 25 is arranged on the output end light path of the second-harmonic crystal 23, the second light absorption bucket 27 is arranged on the transmission light path of the third dichroic mirror 25, the fourth dichroic mirror 26 is arranged on the reflection light path of the third dichroic mirror 25, the output light path of the fourth dichroic mirror 26 is connected with the input end light path of the collimating mirror 28, and the output end of the collimating mirror 28 is taken as the output end of the frequency doubling output unit 500 to output laser light with a required spot size.

[0052] In the embodiment, the first dichroic mirror 20 and the second dichroic mirror 21 are completely identical in specification, transmit 976nm laser light and reflect 1064nm laser light; the third dichroic mirror 25 and the fourth dichroic mirror 26 are completely identical in specification, transmit 1064nm wavelength laser light and reflect 532nm laser light; the focusing mirror 22 has a focal length of 50-100mm; the second-harmonic crystal 23 has a length of 15-25mm and is made of lithium triborate; and the collimating mirror 28 has a focal length of 50-300mm. The first light absorption bucket 24 absorbs residual 976nm laser light, and the second light absorption bucket 27 absorbs 1064nm laser light.

[0053] The above only describes the preferred embodiments of the present application and should not be used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

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 frequency, 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; The secondary amplification unit (300) is optically connected to the output end of the primary amplification unit (200) and is used to further power-amplify the seed light amplified by the primary amplification unit (200); 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); The frequency doubling output unit (500) is optically connected to the output end of the three-stage amplification unit (400) and is used to perform frequency doubling and wavelength selection on the laser light obtained by the third power amplification, and output green laser light with a specified divergence angle and spot size; 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) and outputs 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; 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 connected to the output end optical path 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 connected to the first end optical path of the first polarization-maintaining pump combiner (7); the second end of the first polarization-maintaining pump combiner (7) is connected to the output end optical path of the first pump source (8); the third end of the first polarization-maintaining pump combiner (7) is connected to the input end optical path of the second polarization-maintaining optical isolator (9); the output end of the second polarization-maintaining optical isolator (9) serves as the output end of the first-stage amplification unit (200) to output the laser light after power amplification; the second polarization-maintaining optical isolator (9) is used to eliminate reflected light in the optical path; The second polarization-maintaining optical isolator (9) passes through a slow axis, that is, the phase modulator (3) adopts a design of passing through a fast axis, while the laser seed signal light passes through a slow axis, thereby improving the polarization extinction ratio of the signal light.

2. A high-power fiber green laser according to claim 1, 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), and the second polarization-maintaining gain optical fiber (11) is optically connected to the output end of the second polarization-maintaining gain optical isolator (9). The other end of the 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) serves as the output end of the secondary amplification unit (300) to output the laser light after secondary power amplification, and the third polarization-maintaining optical isolator (14) 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 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 the third pump source (16) and the 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 the optical path of one end of the third polarization-maintaining gain fiber (18), the other end of the third polarization-maintaining gain fiber (18) is fused together with one end of the 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.

4. A high-power fiber green laser according to claim 3, 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 provided on the transmission light path of the first dichroic mirror (20); the second dichroic mirror (21) is provided on the reflection light path of the first dichroic mirror (20); and the fourth dichroic mirror (26) is provided on the second light absorption barrel (27). 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 provided on the transmitted light path of the third dichroic mirror (25), and a fourth dichroic mirror (26) is provided 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 the 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.

5. The high-power fiber green laser according to claim 4, 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.

6. The high-power fiber green laser according to claim 4, 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.

7. The high-power fiber green laser according to claim 4, characterized in that: The first dichroic mirror (20) and the second dichroic mirror (21) have the same specifications, transmit 976nm laser light and reflect 1064nm laser light; the third dichroic mirror (25) and the fourth dichroic mirror (26) have the same specifications, transmit 1064nm wavelength laser light and reflect 532nm laser light.

8. The high-power fiber green laser according to claim 4, characterized in that: The focal length of the focusing mirror (22) is 50-100 mm; the length of the frequency doubling crystal (23) is 15-25 mm; and the focal length of the collimating mirror (28) is 50-300 mm.

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