Kilowatt-level 2-micron all-fiber laser

Abstract

The utility model discloses a kilowatt-level 2 [mu] m all-fiber laser, which can control the contour and the line width of a 2 [mu] m wave band laser line, realize line width tuning and stimulated Brillouin scattering suppression, realize 2 [mu] m wave band laser power improvement, is compact in structure and high in intelligent degree, and makes up the technical defects of the type of laser sources at home and abroad at present. The kilowatt-level 2-micron all-fiber laser comprises a laser line width modulation broadening module (10), a first-stage pre-amplifier (20), a second-stage pre-amplifier (30), a third-stage pre-amplifier (40) and a fourth-stage main amplifier (50) which are sequentially arranged along a light path.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of laser, especially a kilowatt 2mu all fiber laser. BACKGROUND

[0002] 2mu mid-infrared waveband is in the extremely important electromagnetic spectrum interval, has the characteristics of high transmittance and low scattering, thereby has important application value in laser radar, infrared countermeasure, high resolution molecular spectroscopy, nonlinear frequency conversion and medical field, especially in some special scene application, the line width and power of 2mu waveband laser are higher requirement.

[0003] At present, the seed source master oscillator power amplifier technology is usually adopted to improve the output power scale of 2mu waveband narrow line width laser. However, the stimulated Brillouin scattering effect threshold in the optical fiber is low, which has become the key factor limiting the further improvement of the output power of 2mu waveband narrow line width laser. In the case of generally using commercial gain optical fiber, the line width of the seed source is widened, which is an important technical means to reduce the stimulated Brillouin scattering threshold limitation of the laser system. The conventional multi-longitudinal mode oscillation resonant cavity seed source can widen the 2mu waveband seed source line width to tens of MHz, but the frequency longitudinal modes in the resonant cavity have random phases, so that the spectral line width is widened due to multiple nonlinear effects and strong intensity noise appears in the time domain in the process of improving the laser power, which hinders the further improvement of the laser power. The multi-longitudinal mode oscillation resonant cavity seed source is limited by the fixed cavity length of the oscillator, and the line width is fixed and cannot be tuned. In addition, the quantum efficiency of the 2mu waveband optical fiber laser is low, and the thermal load is high, so that the transverse mode instability effect is easily induced in the process of improving the laser power, which leads to the decline of the beam quality, reduces the stability and efficiency of the laser. Limited by the above technical difficulties, the output power of the current domestic and foreign 2mu waveband laser super narrow line width (<10GHz level) high power optical fiber laser is less than kilowatt level, and the laser line width is fixed and cannot be tuned. UTILITY MODEL CONTENTS

[0004] In order to overcome the defects of the prior art, the technical problem to be solved by the utility model is to provide a kilowatt 2mu all fiber laser, which can control the 2mu waveband laser spectral line profile and line width, realize line width tuning and stimulated Brillouin scattering suppression, realize 2mu waveband laser power improvement, and has compact structure and high intelligent degree, which makes up for the technical deficiency of the current domestic and foreign laser source of this type.

[0005] The technical scheme of the utility model is as follows: the kilowatt 2mu all fiber laser comprises a laser line width modulation and widening module (10), a first stage preamplifier (20), a second stage preamplifier (30), a third stage preamplifier (40) and a fourth stage main amplifier (50) arranged in sequence along the light path.

[0006] In the laser linewidth modulation broadening module, an arbitrary waveform generator (103) loads a generated radio frequency signal to a radio frequency power amplifier (104), the radio frequency power amplifier enhances the radio frequency power of the radio frequency signal, the amplified radio frequency signal is loaded to a phase modulator (102), a single-frequency fiber laser (101) injects single-frequency laser into the phase modulator and completes phase modulation, and a controller (105) adjusts the bias value of the radio frequency amplifier to control the phase modulator depth, so that the linewidth of the broadened laser is tuned;

[0007] In the first-stage pre-amplifier, the first 793nm semiconductor laser (202) is coupled with the first fiber combiner (201) to pump the first thulium-doped gain fiber (203) to generate gain to form laser amplification and form second-stage pre-amplification light.

[0008] In the second-stage pre-amplifier, the second fiber combiner (301) couples the pump light output by the second 793nm semiconductor laser (302) into the light path to pump the second thulium-doped gain fiber (303) to generate gain to form laser amplification and form second-stage pre-amplification light.

[0009] In the third-stage pre-amplifier, the third fiber combiner (401) couples the pump light output by the third 793nm semiconductor laser (402) into the light path to pump the third thulium-doped gain fiber (403) to generate gain to form laser amplification and form third-stage pre-amplification light. In the fourth-stage main amplifier, the mode field adapter (501) matches the mode field between the optical fiber of the previous-stage amplifier and the optical fiber of the current-stage amplifier to realize low-loss connection of the system, the first cladding light stripper (502) strips the cladding light that is reversely transmitted in the optical fiber cladding in the current-stage amplifier, the fourth 793nm semiconductor laser (504) and the fourth fiber combiner (503) are connected by optical fibers to input forwardly transmitted pump laser, the fifth 793nm semiconductor laser (507) and the fifth fiber combiner (506) are connected by optical fibers to input reversely transmitted pump laser, the output optical fiber pigtail of the fourth fiber combiner is fused to the front end of the fourth thulium-doped gain fiber (505), and the input optical fiber pigtail of the fifth fiber combiner is fused to the rear end of the fourth thulium-doped gain fiber, so that kilowatt-level 2-micron laser output is generated by the common gain, and the second cladding light stripper (508) strips the cladding light that is forwardly transmitted in the optical fiber cladding in the current-stage amplifier.

[0010] Compared with the prior art, the utility model can achieve the following technical effects:

[0011] 1. The utility model realizes kilowatt-level high-power output of a 2-micron waveband narrow linewidth (<10GHz order) laser with full fiber, has the advantages of compact structure, high integration level, high stability and good beam quality, is not sensitive to vibration and other interference factors in the working environment, and greatly improves the stability and reliability of the laser operation.

[0012] 2. The single radio frequency signal or multiple types of hybrid radio frequency signal is used to modulate the flat spectrum of the single-pole laser phase, and the threshold of the stimulated Brillouin scattering of the 2μm waveband laser system is significantly improved.

[0013] 3. The line width of the 2μm waveband laser is flexible and adjustable, the system has high intelligence, and the initial flat spectrum modulation and line width tuning can be realized quickly. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The structure schematic diagram of the kilowatt 2μm all-fiber laser according to the utility model is shown.

[0015] Figure 2 For Figure 1 The structure schematic diagram of the laser line width modulation and broadening module.

[0016] Figure 3 For Figure 1 The structure schematic diagram of the first-stage preamplifier.

[0017] Figure 4 For Figure 1 The structure schematic diagram of the second-stage preamplifier.

[0018] Figure 5 For Figure 1 The structure schematic diagram of the third-stage preamplifier.

[0019] Figure 6 For Figure 1 The structure schematic diagram of the fourth-stage main amplifier.

[0020] In the figure:

[0021] 10, laser line width modulation and broadening module; 101, single-frequency fiber laser; 102, phase modulator; 103, arbitrary waveform generator; 104, radio frequency power amplifier; 105, controller;

[0022] 20, first-stage preamplifier; 201, first fiber combiner; 202, first 793nm semiconductor laser; 203, first thulium-doped gain fiber; 204, first fiber isolator;

[0023] 30, second-stage preamplifier; 301, second fiber combiner; 302, second 793nm semiconductor laser; 303, second thulium-doped gain fiber; 304, second fiber isolator;

[0024] 40, third-stage preamplifier; 401, third fiber combiner; 402, third 793nm semiconductor laser; 403, third thulium-doped gain fiber; 404, third fiber isolator; 405, fiber circulator;

[0025] 50. Fourth-stage main amplifier; 501. Mode field adapter; 502. First cladding optical stripper; 503. Fourth fiber combiner; 504. Fourth 793nm semiconductor laser; 505. Fourth thulium-doped gain fiber; 506. Fifth fiber combiner; 507. Fifth 793nm semiconductor laser; 508. Second cladding optical stripper; 509. High-power output adapter. Detailed Implementation

[0026] like Figures 1-6 As shown, this kilowatt-level 2μm all-fiber laser includes a laser linewidth modulation and stretching module 10, a first-stage preamplifier 20, a second-stage preamplifier 30, a third-stage preamplifier 40, and a fourth-stage main amplifier 50 arranged sequentially along the optical path.

[0027] In the laser linewidth modulation and stretching module, the arbitrary waveform generator 103 loads the generated radio frequency signal onto the radio frequency power amplifier 104. The radio frequency power amplifier boosts the radio frequency power of the radio frequency signal. The amplified radio frequency signal is then loaded onto the phase modulator 102. The single-frequency fiber laser 101 injects the single-frequency laser into the phase modulator, which then performs phase modulation. The controller 105 adjusts the bias voltage of the radio frequency amplifier to control the depth of the phase modulator, thereby achieving laser linewidth tuning after stretching.

[0028] In the first-stage preamplifier, the first 793nm semiconductor laser 202 is coupled to the first fiber combiner 201 to pump the first thulium-doped gain fiber 203, generating gain to form laser amplification and forming the second-stage preamplified light.

[0029] In the second-stage preamplifier, the second fiber combiner 301 couples the pump light output from the second 793nm semiconductor laser 302 into the optical path, pumps the second thulium-doped gain fiber 303, generates gain to form laser amplification, and forms the second-stage preamplified light;

[0030] In the third stage pre-amplifier, the third optical fiber combiner 401 couples the pump light output by the third 793nm semiconductor laser 402 into the light path, pumps the third thulium-doped gain optical fiber 403, generates gain to form laser amplification, and forms the third stage pre-amplification light; in the fourth stage main amplifier, the mode field adapter 501 matches the mode field between the optical fiber of the last stage amplifier and the optical fiber of the current stage amplifier to realize low-loss connection of the system, the first cladding light stripper 502 strips the cladding light in the optical fiber cladding which is reversely transmitted in the current stage amplification, the fourth 793nm semiconductor laser 504 and the fourth optical fiber combiner 503 are connected by optical fibers to input forward transmission pump laser, the fifth 793nm semiconductor laser 507 and the fifth optical fiber combiner 506 are connected by optical fibers to input reverse transmission pump laser, the output optical fiber pigtail of the fourth optical fiber combiner is fused to the front end of the fourth thulium-doped gain optical fiber 505, and the input optical fiber pigtail of the fifth optical fiber combiner is fused to the rear end of the fourth thulium-doped gain optical fiber, so that kilowatt-level 2-micron laser output is generated by gain together, and the second cladding light stripper 508 strips the cladding light in the optical fiber cladding which is forwardly transmitted in the current stage amplification.

[0031] Compared with the prior art, the utility model can obtain the following technical effects:

[0032] 1. The utility model realizes kilowatt-level high-power output of 2-micron band narrow line width (<10GHz order of magnitude) laser of full optical fiber, has the advantages of compact structure, high integration degree, high stability and good beam quality, is not sensitive to vibration and other interference factors in the working environment, and greatly improves the stability and reliability of the laser operation.

[0033] 2. Single radio frequency signal or multiple types of mixed radio frequency signals are used to flatten and broaden the spectrum through single-pole laser phase modulation, and the stimulated Brillouin scattering threshold of the 2-micron band laser system is significantly improved.

[0034] 3. The line width of the 2-micron band laser is flexibly adjustable, the system has high intelligence, and fast initial flat spectrum modulation and line width tuning can be realized.

[0035] Preferably, the arbitrary waveform generator is a signal generation module composed of a field programmable gate array (FPGA) and a digital-to-analog converter (DAC) to generate multiple different types of radio frequency driving signals, including single radio frequency signals of pseudo-random signals, sinusoidal signals, white noise signals or radio frequency signals after different combinations of the above signals.

[0036] Preferably, the first optical fiber combiner is connected with a first optical fiber isolator 204.

[0037] Preferably, the second optical fiber combiner is connected with a second optical fiber isolator 304.

[0038] Preferably, the third optical fiber combiner is sequentially connected with a third optical fiber isolator 404 and an optical fiber circulator 405.

[0039] Preferably, a high-power output adapter 509 is welded after the second cladding light stripper.

[0040] Preferably, the fourth-stage main amplifier is bidirectional pumped.

[0041] The content of the present application will be described in more detail below.

[0042] Referring to Figures 1-6 The utility model provides a tunable super narrow line width's 2mu high power fiber laser, including laser line width modulation broadening module 10, first stage preamplifier 20, second stage preamplifier 30, third stage preamplifier 40 and fourth stage main amplifier 50 that are sequentially arranged along the light path, wherein, laser line width modulation broadening module 10 includes single frequency fiber laser 101, phase modulator 102, arbitrary waveform generator 103, radio frequency power amplifier 104 and controller 105, first stage preamplifier 20 includes first optical fiber combiner 201, first 793nm semiconductor laser 202, first thulium doped gain fiber 203 and first optical fiber isolator 204, second stage preamplifier 30 includes second optical fiber combiner 301, second 793nm semiconductor laser 302, second thulium doped gain fiber 303 and second optical fiber isolator 304, third stage preamplifier 40 includes third optical fiber combiner 401, third 793nm semiconductor laser 402, third thulium doped gain fiber 403, third optical fiber isolator 404 and optical fiber circulator 405, fourth stage main amplifier 50 includes mode field adapter 501, first cladding light stripper 502, fourth optical fiber combiner 503, fourth 793nm semiconductor laser 504, fourth thulium doped gain fiber 505, fifth optical fiber combiner 506, fifth 793nm semiconductor laser 507, second cladding light stripper 508 and high-power output adapter 509.

[0043] The functions of the above components are as follows:

[0044] The laser line width modulation broadening module 10 is used for tuning and broadening the line width of the single frequency fiber laser.

[0045] The single frequency fiber laser 101 is used for generating continuous and stable single frequency 2mu laser.

[0046] The phase modulator 102 is used for phase modulating the single frequency fiber laser.

[0047] The arbitrary waveform generator 103 is used for generating RF driving signals.

[0048] a radio frequency power amplifier 104 for amplifying the power of the RF drive signal;

[0049] a controller 105 for tuning the bias voltage of the radio frequency power amplifier;

[0050] a first-stage preamplifier 20 for amplifying the first-stage preamplified light after the line-width modulation and broadening of the laser light;

[0051] a first optical fiber combiner 201 for coupling the pump light and connecting the post-stage amplification structure;

[0052] a first 793 nm semiconductor laser 202 for pumping the single-mode thulium-doped optical fiber to generate gain;

[0053] a first thulium-doped gain optical fiber 203 for providing gain in the first-stage preamplifier;

[0054] a first optical fiber isolator 204 for preventing the feedback light of the second-stage preamplifier from damaging the devices in the system;

[0055] a second-stage preamplifier 30 for amplifying the first-stage preamplified laser light to generate second-stage preamplified light;

[0056] a second optical fiber combiner 301 for connecting the pump laser and the gain optical fiber in the stage;

[0057] a second 793 nm semiconductor laser 302 for pumping the gain optical fiber in the second-stage preamplifier to generate laser light;

[0058] a second thulium-doped gain optical fiber 303 for providing gain medium in the second-stage preamplifier;

[0059] a second optical fiber isolator 304 for preventing the feedback light of the third-stage preamplifier from damaging the devices in the system;

[0060] a third-stage preamplifier 40 for amplifying the second-stage preamplified laser light to generate third-stage preamplified light;

[0061] a third optical fiber combiner 401 for connecting the pump laser and the gain optical fiber in the stage;

[0062] a third 793 nm semiconductor laser 402 for pumping the gain fiber in the third-stage preamplifier to generate laser light;

[0063] a third thulium-doped gain optical fiber 403 for providing gain medium in the third-stage preamplifier;

[0064] a third optical fiber isolator 404 for preventing the feedback light of the next-stage amplifier from damaging the devices in the system;

[0065] Optical fiber circulator 405 is used to filter and monitor the scattered light transmitted reversely in the fourth stage main amplifier;

[0066] Fourth stage main amplifier 50 is used to amplify the third stage pre-amplified light to generate fourth stage main amplified light;

[0067] Mode field adapter 501 is used to match the optical field mode between the output optical fiber of the third stage pre-amplifier and the input optical fiber of the current stage;

[0068] First cladding light stripper 502 is used to strip the cladding light transmitted reversely in the current stage amplifier;

[0069] Fourth optical fiber combiner 503 is used to connect the forward pumping laser and the front end of the gain optical fiber of the current stage;

[0070] Fourth 793nm semiconductor laser 504 is used to forward pump the gain fiber of the fourth stage amplifier to generate laser;

[0071] Fourth thulium-doped gain optical fiber 505 is used to provide gain medium in the main amplifier;

[0072] Fifth optical fiber combiner 506 is used to connect the backward pumping laser and the rear end of the gain optical fiber of the current stage;

[0073] Fifth 793nm semiconductor laser 507 is used to backward pump the gain fiber of the fourth stage amplifier to generate laser;

[0074] Second cladding light stripper 508 is used to strip the cladding light transmitted forwardly in the current stage amplifier;

[0075] Adapter 509 is used for high-power laser collimation output.

[0076] The connection relationship of the above-mentioned components is as follows:

[0077] The laser linewidth modulation and broadening module 10 comprises a first stage pre-amplifier 20, a second stage pre-amplifier 30, a third stage pre-amplifier 40 and a fourth stage main amplifier 50 arranged in sequence along an optical path; a single-frequency fiber laser 01 is injected into a phase modulator 02 for phase modulation; an arbitrary waveform generator 03 is connected to the phase modulator 02 through a radio frequency power amplifier 04 to provide a radio frequency signal for the phase modulator 02; and a controller 05 is connected to the radio frequency power amplifier 04 to tune the bias value.

[0078] Further, the RF signal generated by the arbitrary waveform generator can be a sinusoidal signal, a pseudo-random signal, a white noise signal and other multi-frequency signals used for modulation and broadening;

[0079] Further, the embodiment adopts a PRBS signal and sine signal hybrid phase modulation method, after synchronous phase modulation, the frequency spectrum overlaps each other, while realizing spectrum broadening, filling the spectral line interval of sine phase modulation, presenting better near flat top form than single stage PRBS phase modulation, obtaining better SBS suppression effect, and programming the PRBS and sine modulation parameters, realizing high-precision tunable of spectral line width and regulation and control of spectral profile.

[0080] The first-stage pre-amplifier is sequentially provided with a first optical fiber combiner 201, a first 793nm semiconductor laser 202, a first thulium-doped gain optical fiber 203 and a first optical fiber isolator 204 along an optical path; the first optical fiber combiner 201 is low-loss fused with the first 793nm semiconductor laser 202 through an optical fiber, the first optical fiber combiner 201 performs core pumping on the first thulium-doped gain optical fiber 203 to generate laser amplification; the first optical fiber isolator 204 is used in the optical path to avoid adverse effects of backward transmission light in the optical path on devices and systems.

[0081] The second-stage pre-amplifier is sequentially provided with a second optical fiber combiner 301, a second thulium-doped gain optical fiber 303 and a second optical fiber isolator 304 along an optical path, and a second 793nm semiconductor laser 302 connected with the second optical fiber combiner 301 through an optical fiber; the second 793nm semiconductor laser 302 is connected with the second thulium-doped gain optical fiber 303 through an optical fiber to input pump laser, an output optical fiber tail fiber of the second optical fiber combiner 301 is fused with the second thulium-doped gain optical fiber 303 to generate gain and form laser amplification, and the second optical fiber isolator 304 is used in the optical path to avoid adverse effects of backward transmission light in the optical path on devices and systems.

[0082] The third-stage pre-amplifier is sequentially provided with a third optical fiber combiner 401, a third thulium-doped gain optical fiber 403, a third optical fiber isolator 404, an optical fiber circulator 405 along an optical path, and a third 793nm semiconductor laser 402 connected with the third optical fiber combiner 401 through an optical fiber; the third 793nm semiconductor laser 402 is connected with the third optical fiber combiner 401 through an optical fiber to input pump laser, an output optical fiber tail fiber of the third optical fiber combiner 401 is fused with the third thulium-doped gain optical fiber 403 to generate gain and form further laser amplification, the third optical fiber isolator 404 is used in the optical path to avoid adverse effects of backward transmission light in the optical path on devices and systems, and the optical fiber circulator 405 filters and monitors scattered laser transmitted in reverse in the next-stage optical path.

[0083] The fourth-stage main amplifier comprises, in sequence along an optical path, a mode field adapter 501, a first cladding light stripper 502, a fourth optical fiber combiner 503, a fourth 793nm semiconductor laser 504, a fourth thulium-doped gain optical fiber 505, a fifth optical fiber combiner 506, a fifth 793nm semiconductor laser 507, a second cladding light stripper 508, and an adapter 509, and the fourth 793nm semiconductor laser 504 is connected to the fourth optical fiber combiner 503 through an optical fiber, and the fifth 793nm semiconductor laser 507 is connected to the fifth optical fiber combiner 506 through an optical fiber; the mode field adapter 501 is used for matching the mode field between the last-stage amplifier and the current-stage amplifier to facilitate low-loss connection of the system, the first cladding light stripper 502 is used for stripping the cladding light reversely transmitted in the cladding of the optical fiber in the current-stage amplification, the fourth 793nm semiconductor laser 504 is connected to the fourth optical fiber combiner 503 through an optical fiber to input forwardly transmitted pump laser, the fifth 793nm semiconductor laser 507 is connected to the fifth optical fiber combiner 506 through an optical fiber to input reversely transmitted pump laser, the output optical fiber tail fiber of the fourth optical fiber combiner 503 is fused to the front end of the fourth thulium-doped gain optical fiber 505, and the input optical fiber tail fiber of the fifth optical fiber combiner 506 is fused to the rear end of the fourth thulium-doped gain optical fiber 505, so that gain is generated together to form kilowatt-level high-power 2μm laser output, and the second cladding light stripper 508 is used for stripping the cladding light forwardly transmitted in the cladding of the optical fiber in the current-stage amplification. In order to prevent the narrow-line-width high-power laser output from damaging the gain fiber, a high-power output adapter 509 is fused after the second cladding light stripper 508.

[0084] Further, the fourth-stage main amplifier is bidirectional pumped.

[0085] The specific working process of the utility model is as follows:

[0086] In the laser line width modulation and broadening module, the radio frequency signal generated by the arbitrary waveform generator is mixed (pseudo-random signal and sine signal) and loaded to the radio frequency amplifier, the radio frequency amplifier improves the radio frequency power of the radio frequency signal, the amplified radio frequency signal is loaded to the phase modulator, the single-frequency fiber laser injects single-frequency laser into the phase modulator and completes phase modulation, the controller adjusts the bias value of the radio frequency amplifier to control the depth of the phase modulator, and the laser line width after broadening is tuned.

[0087] The 2μm narrow-line-width laser after line width broadening enters the first-stage pre-amplification system through the first optical fiber combiner 201, the first 793nm semiconductor laser 202 is coupled with the first optical fiber combiner 201 to pump the first thulium-doped gain optical fiber 203, gain is generated to form laser amplification, and the first optical fiber isolator 204 is connected after that to prevent the influence of the reverse feedback light of the next stage on the system.

[0088] The second stage pre-amplifier is an intermediate stage, which aims to further increase the output power of the laser and ensure good beam quality to provide a high-quality light source for the next stage. The second optical fiber combiner 301 couples the pump light output by the second 793 nm semiconductor laser 302 into the optical path, pumps the second thulium-doped gain fiber 303 to generate laser amplification, and forms a second stage pre-amplification light. The second optical fiber isolator 304 is connected after the second stage pre-amplification light to prevent the reverse feedback light of the next stage from affecting the system.

[0089] The third stage pre-amplifier is also an intermediate stage, which also aims to further increase the output power of the laser and ensure good beam quality to provide a high-quality light source for the main amplification stage. The third optical fiber combiner 401 couples the pump light output by the third 793 nm semiconductor laser 402 into the optical path, pumps the third thulium-doped gain fiber 403 to generate laser amplification, and forms a third stage pre-amplification light. The third optical fiber isolator 404 is connected after the third stage pre-amplification light to prevent the reverse feedback light of the next stage from affecting the system, and the optical fiber ring 405 is used to monitor and filter out the reverse feedback light of the next stage.

[0090] The fourth stage main amplifier is the final output end of the 2 μm ultra-narrow linewidth high-power laser, and the main purpose is to achieve high-power amplification of signal light under different laser linewidths. The mode field adapter 501 is used to match the mode field between the optical fiber of the previous stage amplifier and the optical fiber of the current stage amplifier to facilitate low-loss connection of the system. The first cladding light stripper 502 strips the cladding light that is transmitted in the reverse direction in the optical fiber cladding in the current stage amplification. The fourth 793 nm semiconductor laser 504 and the fourth optical fiber combiner 503 are connected by optical fibers to input forward transmission pump laser. The fifth 793 nm semiconductor laser 507 and the fifth optical fiber combiner 506 are connected by optical fibers to input reverse transmission pump laser. The output optical fiber tail fiber of the fourth optical fiber combiner 503 is fused to the front end of the fourth thulium-doped gain fiber 505, and the input optical fiber tail fiber of the fifth optical fiber combiner 506 is fused to the rear end of the fourth thulium-doped gain fiber 505, which together generates gain to form a kilowatt-level high-power 2 μm laser output. The second cladding light stripper 508 strips the cladding light that is transmitted in the forward direction in the optical fiber cladding in the current stage amplification. In order to prevent the narrow linewidth high-power laser output from damaging the gain fiber, a high-power output adapter 509 is fused after the second cladding light stripper 508, which can withstand kilowatt-level high-power narrow linewidth laser output.

[0091] 2 The utility model discloses a kind of 2μm waveband fiber laser, which is mainly used in the field of laser radar, biological medical treatment, space communication and the like, and has very high requirements on the power of laser.The utility model can significantly improve the stimulated Brillouin scattering threshold of 2μm waveband laser by using single radio frequency signal or multiple types of mixed radio frequency signal to modulate flat spectrum through single laser phase, realize the output of 2μm laser with kilowatt power, and the laser linewidth is continuously adjustable within 3GHz to tens of GHz.The utility model adopts all-fiber structure, so that the device has the advantages of compact structure, high integration, good stability, high conversion efficiency and good beam quality.

[0092] The above is only a preferred embodiment of the utility model, and does not limit the utility model in any form. Any simple modification, equivalent change and modification made according to the technical essence of the utility model to the above embodiment are still within the protection scope of the technical scheme of the utility model.

Claims

1. A kilowatt class 2 pm all-fiber laser characterized in that: It includes laser linewidth modulation broadening module (10), first stage preamplifier (20), second stage preamplifier (30), third stage preamplifier (40) and fourth stage main amplifier (50) arranged in sequence along the light path;In the laser linewidth modulation broadening module, the arbitrary waveform generator (103) loads the generated radio frequency signal to the radio frequency power amplifier (104), the radio frequency power amplifier improves the radio frequency power of the radio frequency signal, the amplified radio frequency signal is loaded to the phase modulator (102), the single frequency fiber laser (101) injects single frequency laser into the phase modulator and completes phase modulation, the controller (105) adjusts the bias value of the radio frequency amplifier to control the phase modulator depth, realizes the linewidth tuning of the broadened laser; In the first stage preamplifier, the first 793nm semiconductor laser (202) is coupled with the first fiber combiner (201), pumps the first thulium-doped gain fiber (203), generates gain to form laser amplification, and forms the second stage preamplification light; In the second stage preamplifier, the second fiber combiner (301) couples the pump light output by the second 793nm semiconductor laser (302) into the light path, pumps the second thulium-doped gain fiber (303), generates gain to form laser amplification, and forms the second stage preamplification light; In the third stage preamplifier, the third fiber combiner (401) couples the pump light output by the third 793nm semiconductor laser (402) into the light path, pumps the third thulium-doped gain fiber (403), generates gain to form laser amplification, and forms the third stage preamplification light; In the fourth stage main amplifier, the mode field adapter (501) matches the mode field between the last stage amplifier and the amplifier fiber to realize low loss connection of the system, the first cladding light stripper (502) strips the cladding light in the optical fiber cladding in the reverse direction in the amplifier, the fourth 793nm semiconductor laser (504) and the fourth fiber combiner (503) are connected by optical fiber to input forward transmission pump laser, the fifth 793nm semiconductor laser (507) and the fifth fiber combiner (506) are connected by optical fiber to input reverse transmission pump laser, the output fiber tail fiber of the fourth fiber combiner is fused with the front end of the fourth thulium-doped gain fiber (505), and the input fiber tail fiber of the fifth fiber combiner is fused with the rear end of the fourth thulium-doped gain fiber, which together generates gain to form kilowatt level 2μm laser output, and the second cladding light stripper (508) strips the cladding light in the optical fiber cladding in the forward direction in the amplifier.

2. The kilo-watt class 2 pm all-fiber laser of claim 1, wherein: The arbitrary waveform generator is a signal generation module composed of field programmable gate array FPGA and digital to analog converter DAC, which is used to generate a plurality of different types of radio frequency driving signals, including: pseudo-random signal, sinusoidal signal, white noise signal single radio frequency signal or radio frequency signal after different combination of the above signals.

3. The kilo-watt class 2 pm all-fiber laser of claim 2, wherein: The first fiber combiner is connected with the first fiber isolator (204) behind.

4. The kilo-watt class 2 pm all-fiber laser of claim 3, wherein: The second fiber combiner is connected with the second fiber isolator (304) behind.

5. The kilo-watt class 2 pm all-fiber laser of claim 4, wherein: The third optical fiber combiner is connected with a third optical fiber isolator (404) and a fiber ring (405) in sequence.

6. The kilo-watt class 2 pm all-fiber laser of claim 1, wherein: A high-power output adapter (509) is fused after the second cladding light stripper.

7. The kilo-watt class 2 pm all-fiber laser of claim 6, wherein: The fourth-stage main amplifier is pumped in a bidirectional manner.

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