Mode instability suppression method and device based on laser time domain control

Abstract

The present invention provides a method and device for suppressing mode instability based on laser time-domain regulation. By detecting the output characteristics of a fiber laser, the current state of the fiber laser and whether the mode instability threshold has been reached are determined. If the threshold is reached, a pulsed pump light sequence that has undergone time-domain regulation is injected into the fiber laser until the mode instability effect in the fiber laser is effectively suppressed, further increasing the output power of the fiber laser. This invention enables fiber lasers to operate stably at higher power levels, meeting the application requirements of high-power lasers.

Description

Technical Field

[0001] The present invention mainly relates to the field of optical fiber laser technology, and in particular to a method and device for suppressing mode instability based on laser time domain regulation. Background Art

[0002] In the development and application of high-power fiber lasers, mode instability is a common phenomenon, seriously threatening the stability of the lasers, reducing the output beam quality, and significantly limiting further increases in system power. This not only affects the performance of fiber lasers in key areas such as industrial processing, biomedicine, and aerospace, but also poses challenges to the further development and application of related technologies.

[0003] At present, in the field of fiber lasers, some methods and devices for suppressing mode instability have been disclosed. Patent application with publication number CN 208571223U proposes a system for suppressing mode instability in high-power fiber laser amplifiers. By introducing a polarization control system, the proportion of high-order modes injected and transmitted longitudinally along the gain fiber is reduced, thereby suppressing the mode instability effect in high-power fiber laser amplifiers. Patent application with publication number CN 212485781U describes a gain fiber group and fiber amplifier that suppress nonlinear and mode instability effects. By designing the curvature radius of multiple arc-shaped gain fiber segments, the beam quality of the fiber laser amplifier is improved and the nonlinear effect is effectively suppressed. Patent application with publication number CN 115313138A proposes a system and method for actively suppressing fiber laser mode instability. By controlling the frequency shift between the high-order mode and the fundamental mode through beam splitting, the inter-modal interference in the fiber amplifier is destroyed, and the generation of mode instability effects is suppressed. Patent application CN 111916984A introduces a fiber laser system with a mode instability suppression function. It uses a few-mode fiber Bragg grating and a high-order mode filter to change the pump light wavelength and appropriately increase the proportion of backward pump light energy to increase the fiber laser's mode instability threshold and boost output power.

[0004] However, these modal instability suppression methods typically involve physical modifications to the fiber laser's optical path or structure, which not only increases system complexity and cost but is also challenging to implement on existing fiber lasers. Furthermore, these methods often struggle to adapt to rapidly changing operating conditions in practical applications, resulting in cumbersome adjustments and slow response times, making it difficult to accurately lock in the optimal suppression parameters.

[0005] With the development of laser technology, the requirements for laser performance are becoming increasingly stringent, especially in terms of beam quality and power stability. Therefore, there is an urgent need for new methods and devices that can effectively suppress mode instability effects while maintaining cost-effectiveness and operational flexibility. Summary of the Invention

[0006] In view of the technical problems existing in the prior art, the present invention provides a method and device for suppressing mode instability based on laser time domain regulation.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a mode instability suppression method based on laser time domain regulation. The fiber laser includes one or more continuous pump light sources and one or more time domain modulated pump light sources. The time domain modulated pump light sources are used to output a pulsed pump light sequence that has undergone time domain regulation. By detecting the output characteristics of the fiber laser, the current state of the fiber laser and whether the mode instability threshold has been reached are determined. If the mode instability threshold has been reached, the pulsed pump light sequence that has undergone time domain regulation is injected into the fiber laser. The pump light modulation parameters of each time domain modulated pump light source are continuously changed based on a control algorithm. The pump light modulation parameters of the time domain modulated pump light source include the amplitude, frequency, duty cycle, waveform and / or modulation depth of the pulsed pump light sequence. The output characteristics of the fiber laser are synchronously detected until it is detected that the laser output power of the fiber laser continues to increase linearly, the time domain is stable, the frequency domain characteristic peaks only have the repetition frequency and its multiple frequency corresponding to the pump modulation, and the mode instability phenomenon disappears. In this way, the mode instability effect in the fiber laser is effectively suppressed, and the output power of the fiber laser is further improved.

[0009] The fiber laser in the present invention is not limited to any type. Further, the fiber laser includes but is not limited to a fiber laser oscillator, a fiber laser amplifier, an integrated oscillator-amplifier fiber laser, and a fiber laser with a single-ended output or a double-ended output structure, and the fiber laser is suitable for high-power output.

[0010] Preferably, the fiber laser is a single-ended output fiber laser oscillator, comprising a first pump signal combiner, a first fiber Bragg grating, a first gain fiber, a second fiber Bragg grating, a second pump signal combiner, a first cladding light filter, and a first fiber end cap; a first pump light source is connected to a pump input arm of the first pump signal combiner, and a second pump light source is connected to a pump input arm; a third pump light source is connected to a pump input arm of the second pump signal combiner, and a fourth pump light source is connected to a pump input arm, wherein the first pump light source and the third pump light source are continuous pump light sources, and the second pump light source and the fourth pump light source are time-domain modulated pump light sources, and the time-domain modulated pump light source is used to output a pulsed pump light sequence for time-domain regulation;

[0011] The pump output arm of the first pump signal combiner, the first fiber Bragg grating, the first gain fiber, the second fiber Bragg grating, and the pump output arm of the second pump signal combiner are connected in sequence; the signal output arm of the second pump signal combiner, the first cladding light filter, and the first fiber end cap are connected in sequence; the first fiber end cap serves as the output end of the fiber laser and finally outputs laser.

[0012] Preferably, the fiber laser is a double-ended output fiber laser oscillator, comprising a first pump signal combiner, a first fiber Bragg grating, a first gain fiber, a second fiber Bragg grating, a second pump signal combiner, a first cladding light filter, a first fiber end cap, a second cladding light filter, and a second fiber end cap; a first pump light source is connected to a pump input arm of the first pump signal combiner, and a second pump light source is connected to a pump input arm; a third pump light source is connected to a pump input arm of the second pump signal combiner, and a fourth pump light source is connected to a pump input arm, wherein the first pump light source and the third pump light source are continuous pump light sources, and the second pump light source and the fourth pump light source are time-domain modulated pump light sources, and the time-domain modulated pump light source is used to output a pulsed pump light sequence for time-domain regulation;

[0013] The pump output arm of the first pump signal combiner, the first fiber Bragg grating, the first gain fiber, the second fiber Bragg grating, and the pump output arm of the second pump signal combiner are connected in sequence; the signal output arm of the second pump signal combiner, the first cladding light filter, and the first fiber end cap are connected in sequence; the signal output arm of the first pump signal combiner, the second cladding light filter, and the second fiber end cap are connected in sequence; the first fiber end cap and the second fiber end cap serve as the two output ends of the fiber laser, and ultimately output laser.

[0014] Preferably, the fiber laser includes a first pump signal combiner, a first fiber Bragg grating, a first gain fiber, a second fiber Bragg grating, a second gain fiber, a second pump signal combiner, a first cladding light filter, and a first fiber end cap; a first pump light source is connected to a pump input arm of the first pump signal combiner, and a second pump light source is connected to a pump input arm; a third pump light source is connected to a pump input arm of the second pump signal combiner, and a fourth pump light source is connected to a pump input arm, wherein the first pump light source and the third pump light source are continuous pump light sources, and the second pump light source and the fourth pump light source are time-domain modulated pump light sources;

[0015] The pump output arm of the first pump signal combiner, the first fiber Bragg grating, the first gain fiber, the second fiber Bragg grating, the second gain fiber, and the pump output arm of the second pump signal combiner are connected in sequence; the signal output arm of the second pump signal combiner, the first cladding light filter, and the first fiber end cap are connected in sequence; the first fiber end cap serves as the output end of the fiber laser and ultimately outputs laser.

[0016] Preferably, the fiber laser includes a first pump signal combiner, a first fiber Bragg grating, a first gain fiber, a second fiber Bragg grating, a second cladding light filter, a second pump signal combiner, a second gain fiber, a third pump signal combiner, a first cladding light filter, and a first fiber end cap;

[0017] A first pump light source is connected to one pump input arm of the first pump signal combiner, and a second pump light source is connected to one pump input arm; a fourth pump light source is connected to one pump input arm of the second pump signal combiner, and a third pump light source is connected to one pump input arm of the third pump signal combiner, wherein the second pump light source is a time-domain modulated pump light source, and the first pump light source, the third pump light source, and the fourth pump light source are all continuous pump light sources;

[0018] The pump output arm of the first pump signal combiner, the first fiber Bragg grating, the first gain fiber, the second fiber Bragg grating, the second cladding optical filter, the signal output arm of the second pump signal combiner, the second gain fiber, and the pump output arm of the third pump signal combiner are connected in sequence; the signal output arm of the third pump signal combiner, the first cladding optical filter, and the first fiber end cap are connected in sequence; the first fiber end cap serves as the output end of the fiber laser and ultimately outputs laser.

[0019] Preferably, the fiber laser includes a first pump signal combiner, a first fiber Bragg grating, a first gain fiber, a second fiber Bragg grating, a second pump signal combiner, a first cladding light filter, a first fiber end cap, a second cladding light filter, a first phase modulator, a second phase modulator, and a polarization combiner; a first pump light source is connected to a pump input arm of the first pump signal combiner, and a second pump light source is connected to a pump input arm; a third pump light source is connected to a pump input arm of the second pump signal combiner, and a fourth pump light source is connected to a pump input arm, wherein the first pump light source and the third pump light source are continuous pump light sources, and the second pump light source and the fourth pump light source are time-domain modulated pump light sources;

[0020] The pump output arm of the first pump signal combiner, the first fiber Bragg grating, the first gain fiber, the second fiber Bragg grating, and the pump output arm of the second pump signal combiner are connected in sequence; the signal output arm of the second pump signal combiner, the first cladding optical filter, and the input end of the second phase modulator are connected in sequence; the signal output arm of the first pump signal combiner, the second cladding optical filter, and the input end of the first phase modulator are connected in sequence; the output end of the first phase modulator and the output end of the second phase modulator are both connected to the polarization combiner, and the polarization combiner is connected to the first fiber end cap, which serves as the output end of the fiber laser and ultimately outputs laser.

[0021] On the other hand, the present invention proposes a mode instability suppression device based on laser time domain regulation, comprising a fiber laser, a mode instability detection module, and a control module;

[0022] The fiber laser includes one or more continuous pump light sources and one or more time-domain modulated pump light sources, wherein the time-domain modulated pump light sources are used to output a pulsed pump light sequence that has been time-domain regulated;

[0023] The mode instability detection module is used to detect the output characteristics of the fiber laser in real time;

[0024] The control module determines the current state of the fiber laser and whether the mode instability threshold is reached based on the detected output characteristics. If the mode instability threshold is reached, a pulsed pump light sequence that has been time-domain modulated is injected into the fiber laser, and the pump light modulation parameters of each time-domain modulated pump light source are continuously changed based on the control algorithm. The pump light modulation parameters of the time-domain modulated pump light source include the amplitude, frequency, duty cycle, waveform and / or modulation depth of the pulsed pump light sequence. The output characteristics of the fiber laser are synchronously detected until it is detected that the laser output power of the fiber laser continues to increase linearly, the time domain is stable, the frequency domain characteristic peaks only have the repetition frequency and its multiple frequency corresponding to the pump modulation, and the mode instability phenomenon disappears. In this way, the mode instability effect in the fiber laser is effectively suppressed, and the output power of the fiber laser is further improved.

[0025] The fiber laser in the present invention is not limited to any type. Further, the fiber laser includes but is not limited to a fiber laser oscillator, a fiber laser amplifier, an integrated oscillator-amplifier fiber laser, and a fiber laser with a single-ended output or a double-ended output structure, and the fiber laser is suitable for high-power output.

[0026] Furthermore, the mode instability detection module is used to detect the laser output characteristics caused by mode instability in real time. The output laser characteristics detected by the mode instability detection module include but are not limited to: power, time domain, mode ratio, and beam quality;

[0027] The control module includes a performance evaluation submodule, a feedback control submodule, and a pump control submodule. The output laser characteristics detected by the mode instability detection module are input into the performance evaluation submodule for analysis and processing. The performance evaluation submodule determines the current state of the fiber laser and whether the mode instability threshold is reached and mode instability occurs based on the laser output characteristic change data detected by the mode instability detection module. The laser characteristic changes after the current fiber laser reaches the mode instability threshold and mode instability occurs include: time domain power fluctuations with a kHz characteristic frequency, laser power stagnation or decline, laser mode dynamic coupling, and rapid decline in beam quality.

[0028] When the performance evaluation submodule determines that the current fiber laser has reached a mode instability threshold and mode instability occurs, the control algorithm run by the feedback control submodule continuously changes the pump light modulation parameters of each time-domain modulated pump light source and transmits them to the pump control submodule, so that each time-domain modulated pump light source injects a pulsed pump light sequence that has been time-domain controlled into the fiber laser, wherein the control algorithm run in the feedback control submodule is linear or nonlinear, including but not limited to: random parallel gradient descent algorithm, hill climbing method, genetic algorithm, simulated annealing algorithm, ant colony algorithm, auto-disturbance rejection control algorithm, PID control algorithm, fuzzy control algorithm, and neural network control algorithm.

[0029] The method of the present invention can achieve the following technical effects:

[0030] 1) The present invention detects the output characteristics of a fiber laser to determine whether the current fiber laser has reached a mode instability threshold. If so, a pulsed pump light sequence that has undergone time-domain modulation is injected into the fiber laser to effectively suppress the mode instability effect of the fiber laser, thereby increasing the mode instability threshold and enabling the laser to operate stably at a higher power level, thus meeting the demand for high-power laser applications such as material processing, laser cutting, and welding.

[0031] 2) The present invention helps to optimize the beam quality of high-power output lasers, reduce the beam divergence angle, and improve the beam brightness, which is particularly important for fields such as precision machining, biomedicine, and scientific research.

[0032] 3) The mode instability detection and control modules described in this invention are designed as external circuits for fiber lasers. This design is compatible with existing fiber laser architectures, eliminating the need for optical path modifications and costly optical component replacement and complex mechanical adjustments, making upgrades and maintenance more convenient. Furthermore, the method's adjustability allows the laser to adapt to varying operating conditions and application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 the structures shown in these drawings without paying any creative work.

[0034] Figure 1 Schematic diagram of the structure of the mode instability suppression device based on laser time domain regulation provided in Example 1;

[0035] Figure 2 Schematic diagram of the structure of the mode instability suppression device based on laser time domain regulation provided in Example 2;

[0036] Figure 3 Schematic diagram of the structure of the mode instability suppression device based on laser time domain regulation provided in Example 3;

[0037] Figure 4 Schematic diagram of the structure of the mode instability suppression device based on laser time domain regulation provided in Example 4;

[0038] Figure 5 Schematic diagram of the structure of the mode instability suppression device based on laser time domain regulation provided in Example 5;

[0039] Figure 6 Schematic diagram of the laser output characteristic change of the mode instability suppression device based on laser time domain regulation provided in Example 2, wherein Figure 6 (a) is the graph showing the laser output power changing with pump power in the first stage. Figure 6 (b) is the time domain and frequency domain diagram after the mode instability occurs in the first stage. Figure 6 (c) is the graph showing the variation of laser output power with pump power in the second stage. Figure 6 (d) Time domain and frequency domain diagrams after the second stage mode instability is suppressed;

[0040] Figure Number:

[0041] 1-1, first pump signal combiner; 1-2, first fiber Bragg grating; 1-3, first gain fiber; 1-4, second fiber Bragg grating; 1-5, second pump signal combiner; 1-6, first cladding optical filter; 1-7, first fiber end cap; 1-8, second cladding optical filter; 1-9, second fiber end cap; 1-10, second gain fiber; 1-11, second cladding optical filter; 1-12, third pump signal combiner; 1-13, first phase modulator; 1-14, second phase modulator; 1-15, polarization combiner;

[0042] 2. First pump light source; 3. First pump light source driving power supply; 4. Second pump light source; 5. Second pump light source driving power supply; 6. Third pump light source; 7. Third pump light source driving power supply; 8. Fourth pump light source; 9. Fourth pump light source driving power supply;

[0043] 10-1, first mode instability detection module; 10-2, second mode instability detection module;

[0044] 11. Control module; 11-1. Performance evaluation submodule; 11-2. Feedback control submodule; 11-3. Pump control submodule. DETAILED DESCRIPTION

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0046] An embodiment of the present invention provides a method for suppressing mode instability based on laser time-domain regulation. By detecting the output characteristics of a fiber laser, the current state of the fiber laser and whether the mode instability threshold has been reached are determined. If the mode instability threshold has been reached, a pulsed pump light sequence that has undergone time-domain regulation is injected into the fiber laser until the mode instability effect in the fiber laser is effectively suppressed, thereby further improving the output power of the fiber laser.

[0047] Specifically, a mode instability suppression method based on laser time domain regulation is provided. The fiber laser includes one or more continuous pump light sources and one or more time domain modulated pump light sources. The time domain modulated pump light sources are used to output a pulsed pump light sequence that has undergone time domain regulation. By detecting the output characteristics of the fiber laser, the current state of the fiber laser and whether the mode instability threshold has been reached are judged. If the mode instability threshold has been reached, the pulsed pump light sequence that has undergone time domain regulation is injected into the fiber laser. The pump light modulation parameters of each time domain modulated pump light source are continuously changed based on a control algorithm. The pump light modulation parameters of the time domain modulated pump light source include the amplitude, frequency, duty cycle, waveform and / or modulation depth of the pulsed pump light sequence. The output characteristics of the fiber laser are synchronously detected until it is detected that the laser output power of the fiber laser continues to increase linearly, the time domain is stable, the frequency domain characteristic peaks only have the repetition frequency and its multiple frequency corresponding to the pump modulation, and the mode instability phenomenon disappears. In this way, the mode instability effect in the fiber laser is effectively suppressed, and the output power of the fiber laser is further improved.

[0048] The fiber laser in the present invention is not limited to any type. Further, the fiber laser includes but is not limited to a fiber laser oscillator, a fiber laser amplifier, an integrated oscillator-amplifier fiber laser, and a fiber laser with a single-ended output or a double-ended output structure, and the fiber laser is suitable for high-power output.

[0049] The gain fiber in the fiber laser of the present invention can be doped with rare earth ions (Er 3+ / Yb 3+ Single-clad, double-clad, triple-clad, or special multi-clad optical fibers (e.g., optical fibers with uniform dimensions, tapered fibers, or fibers with optimized transverse structures, such as limited-doping fibers) can be used. The core and cladding can be configured in any geometric shape. The gain fiber in the fiber laser can, under certain conditions, support transmission in two or more modes.

[0050] Specifically, the mode instability suppression method based on laser time-domain regulation includes:

[0051] (1) The current of the driving power supply of each continuous pump light source in the fiber laser is continuously increased, and the output power of the corresponding continuous pump light source is continuously increased. out The time domain signal of the output laser is collected, and the signal intensity corresponding to the nth time series sampling point is I n , where n = 1, 2, 3, ..., N;

[0052] (2) Determine the mode instability threshold: calculate the mean value of the signal strength Normalized standard deviation According to the formula σ norm (P out )=A·exp(B·P out )+C, where A, B, and C are all constants, and the normalized standard deviation curve σ is obtained by fitting with the output power norm (P out ); let σ norm (P out ) is equal to 0.1‰ / W, which satisfies the threshold judgment condition Where W represents the unit, which means watt; the solution is to obtain the mode instability threshold P CW =P th , P th Indicates that the threshold judgment condition is met P out ;

[0053] (3) When P is detected out =P CW When the current of the driving power supply of each continuous pump light source is stopped, the P out =PCW The current value of the driving power supply of each continuous pump light source remains unchanged;

[0054] (4) setting an initial value of a pump light modulation parameter controlling each time-domain modulated pump light source so that each time-domain modulated pump light source outputs a pulsed pump light sequence corresponding to the pump light modulation parameter;

[0055] (5) In order to find the optimal pump light modulation parameters of the time domain modulated pump light source, the pump light modulation parameters of each time domain modulated pump light source are continuously changed according to the pre-set control algorithm, and the different output powers P corresponding to the pump light modulation parameters of different time domain modulated pump light sources are collected. out The time domain signal of the output laser is x(n), and the signal intensity corresponding to the nth time series sampling point is x(n), where n = 1, 2, 3, ..., N;

[0056] (6) Perform discrete Fourier transform on x(n), that is, Where X(k) is the frequency domain value, k is the sequence index of the frequency domain value; the frequency domain values ​​corresponding to the pump modulation frequency f and all its multiples are set to 0, that is, let X(k i )=0, where k i =mNf·ΔT+1, where m is an integer and ΔT is the sampling interval, and we get X'(k). We do inverse Fourier transform on X'(k) and get x'(n). Let I n = x'(n), and the same method as step (2) is used to calculate the corresponding mode instability threshold P under different time-domain modulation pump light source pump light modulation parameters. QCW =P th ;

[0057] (7) Repeat steps (5)-(7) until the pump light modulation parameters of the time-domain modulated pump light source corresponding to the highest mode instability threshold are found, thereby obtaining a laser output with a higher mode instability threshold. out By P CW Growth to P QCW During the process, the laser output power continues to grow linearly, the time domain is stable, the frequency domain characteristic peaks are only the repetition frequency and its multiples corresponding to the pump modulation, and the mode instability phenomenon disappears.

[0058] In one embodiment, a mode instability suppression device based on laser time domain regulation is provided, comprising a fiber laser, a mode instability detection module, and a control module;

[0059] The fiber laser includes one or more continuous pump light sources and one or more time-domain modulated pump light sources, wherein the time-domain modulated pump light sources are used to output a pulsed pump light sequence that has been time-domain regulated;

[0060] The mode instability detection module is used to detect the output characteristics of the fiber laser in real time;

[0061] The control module determines the current state of the fiber laser and whether the mode instability threshold is reached based on the detected output characteristics. If the mode instability threshold is reached, a pulsed pump light sequence that has been time-domain modulated is injected into the fiber laser, and the pump light modulation parameters of each time-domain modulated pump light source are continuously changed based on the control algorithm. The pump light modulation parameters of the time-domain modulated pump light source include the amplitude, frequency, duty cycle, waveform and / or modulation depth of the pulsed pump light sequence. The output characteristics of the fiber laser are synchronously detected until it is detected that the laser output power of the fiber laser continues to increase linearly, the time domain is stable, the frequency domain characteristic peaks only have the repetition frequency and its multiple frequency corresponding to the pump modulation, and the mode instability phenomenon disappears. In this way, the mode instability effect in the fiber laser is effectively suppressed, and the output power of the fiber laser is further improved.

[0062] Furthermore, the mode instability detection module is used to detect the laser output characteristics caused by mode instability in real time. The output laser characteristics detected by the mode instability detection module include but are not limited to: power, time domain, mode ratio, and beam quality;

[0063] The control module includes a performance evaluation submodule, a feedback control submodule, and a pump control submodule. The output laser characteristics detected by the mode instability detection module are input into the performance evaluation submodule for analysis and processing. The performance evaluation submodule determines the current state of the fiber laser and whether the mode instability threshold is reached and mode instability occurs based on the laser output characteristic change data detected by the mode instability detection module. The laser characteristic changes after the current fiber laser reaches the mode instability threshold and mode instability occurs include: time domain power fluctuations with a kHz characteristic frequency, laser power stagnation or decline, laser mode dynamic coupling, and rapid decline in beam quality.

[0064] When the performance evaluation submodule determines that the current fiber laser has reached a mode instability threshold and mode instability occurs, the control algorithm run by the feedback control submodule continuously changes the pump light modulation parameters of each time-domain modulated pump light source and transmits them to the pump control submodule, so that each time-domain modulated pump light source injects a pulsed pump light sequence that has been time-domain controlled into the fiber laser, wherein the control algorithm run in the feedback control submodule is linear or nonlinear, including but not limited to: random parallel gradient descent algorithm, hill climbing method, genetic algorithm, simulated annealing algorithm, ant colony algorithm, auto-disturbance rejection control algorithm, PID control algorithm, fuzzy control algorithm, and neural network control algorithm.

[0065] The following provides various specific implementations of a mode instability suppression device based on laser time-domain regulation.

[0066] Example 1

[0067] Reference Figure 1 The mode instability suppression device based on laser time domain control provided in Example 1 includes a fiber laser, a first mode instability detection module 10-1 and a control module 11, wherein the control module 11 includes a performance evaluation submodule 11-1, a feedback control submodule 11-2, and a pump control submodule 11-3. The fiber laser includes a first pump signal combiner 1-1, a first fiber Bragg grating 1-2, a first gain fiber 1-3, a second fiber Bragg grating 1-4, a second pump signal combiner 1-5, a first cladding An optical filter 1-6 and a first optical fiber end cap 1-7; a first pump light source 2 is connected to one pump input arm of the first pump signal combiner 1-1, and a second pump light source 4 is connected to one pump input arm; a third pump light source 6 is connected to one pump input arm of the second pump signal combiner 1-5, and a fourth pump light source 8 is connected to one pump input arm, wherein the first pump light source 2 and the third pump light source 6 are continuous pump light sources, and the second pump light source 4 and the fourth pump light source 8 are time-domain modulated pump light sources;

[0068] The pump output arm of the first pump signal combiner 1-1, the first fiber Bragg grating 1-2, the first gain fiber 1-3, the second fiber Bragg grating 1-4, and the pump output arm of the second pump signal combiner 1-5 are connected in sequence; the signal output arm of the second pump signal combiner 1-5, the first cladding light filter 1-6, and the first fiber end cap 1-7 are connected in sequence;

[0069] The first mode instability detection module 10-1 is used to detect the output characteristics of the laser output by the first optical fiber end cap 1-7 in real time, and transmit the detected information to the performance evaluation submodule 11-1;

[0070] The performance evaluation submodule 11-1 determines the current state of the fiber laser and whether it reaches the mode instability threshold based on the information detected by the first mode instability detection module 10-1;

[0071] The feedback control submodule 11-2 is configured to generate pump light modulation parameters based on a preloaded control algorithm according to the current state of the fiber laser and input the parameters to the pump control submodule 11-3. The pump control submodule 11-3 controls the current magnitude and timing characteristics of the driving power supplies of the first pump light source 2, the second pump light source 4, the third pump light source 6, and the fourth pump light source 8, thereby controlling the mode instability threshold. The positive and negative poles of the constant current output cable of the first pump light source driving power supply 3 are connected to the positive and negative poles of the power supply of the first pump light source 2; the positive and negative poles of the constant current output cable of the second pump light source driving power supply 5 are connected to the positive and negative poles of the power supply of the second pump light source 4; the positive and negative poles of the constant current output cable of the third pump light source driving power supply 7 are connected to the positive and negative poles of the power supply of the third pump light source 6; and the positive and negative poles of the constant current output cable of the fourth pump light source driving power supply 9 are connected to the positive and negative poles of the power supply of the fourth pump light source 8. Each driving power supply is configured to drive a corresponding pump light source to generate pump light output of corresponding intensity and timing. The control input ends of the first pump light source driving power supply 3, the second pump light source driving power supply 5, the third pump light source driving power supply 7 and the fourth pump light source driving power supply 9 are respectively connected to the output ends of the pump control submodule 11-3 of the control module 11, wherein the first pump light source 2 and the third pump light source 6 are continuous pump light sources, and the first pump light source driving power supply 3 and the third pump light source driving power supply 7 are continuous driving power supplies; the second pump light source 4 and the fourth pump light source 8 are time domain modulated pump light sources, and the second pump light source driving power supply 5 and the fourth pump light source driving power supply 9 are pulsed driving power supplies.

[0072] The following provides a mode instability suppression process based on laser time domain control according to Example 1:

[0073] (1) The pump control submodule 11-3 controls the current of the first pump light source driving power supply 3 and the third pump light source driving power supply 7 to continuously increase, and the output power of the corresponding first pump light source 2 and the third pump light source 6 to continuously increase. In order to improve the system bandwidth and reduce the cost, the first mode instability detection module 10-1 is generally a high-speed photodetector. out The time domain signal of the output laser is collected, and the signal intensity corresponding to the nth time series sampling point is I n , where n = 1, 2, 3, ..., N;

[0074] (2) The first mode instability detection module 10-1 feeds back the time domain signal to the performance evaluation submodule 11-1 in real time, and determines the mode instability threshold in the performance evaluation submodule 11-1: calculates the mean value of the signal strength Normalized standard deviation According to the formula σ norm (P out )=A·exp(B·P out)+C, where A, B, and C are all constants, and the normalized standard deviation curve σ is obtained by fitting with the output power norm (P out ); let σ norm (P out ) is equal to 0.1‰ / W, which satisfies the threshold judgment condition Where W represents the unit, which means watt; the solution is to obtain the mode instability threshold P CW =P th , P th Indicates that the threshold judgment condition is met P out ;

[0075] (3) When the feedback control submodule 11-2 detects P out =P CW When the current of the first pump light source driving power supply 3 and the third pump light source driving power supply 7 is increased, the pump control submodule 11-3 is controlled to stop increasing the current of the first pump light source driving power supply 3 and the third pump light source driving power supply 7 and to keep the current current values ​​of the first pump light source driving power supply 3 and the third pump light source driving power supply 7 fixed;

[0076] (4) The feedback control submodule 11-2 sets the initial values ​​of the pump light modulation parameters: frequency is 1 kHz, duty cycle is 10%, waveform is square wave, and modulation depth is 100%, and inputs them to the pump control submodule 11-3 to control the second pump light source driving power supply 5 and the fourth pump light source driving power supply 9, so that the second pump light source 4 and the fourth pump light source 8 output pulsed pump light sequences with corresponding parameters.

[0077] (5) In order to find the optimal pump light modulation parameters of the time domain modulated pump light source (the second pump light source 4 and the fourth pump light source 8), the feedback control submodule 11-2 continuously changes the modulation parameters of the time domain modulated pump light source, the second pump light source 4 and the fourth pump light source 8, according to the pre-set control algorithm, and inputs them into the pump control submodule 11-3 in real time. The different output powers P corresponding to the pump light modulation parameters of each group of different time domain modulated pump light sources are out In this case, the first mode instability detection module 10 - 1 uses a high-speed photodetector to collect the time domain signal of the output laser, and the signal intensity corresponding to the nth time series sampling point is x(n), where n=1, 2, 3, …, N;

[0078] (6) In real time, the performance evaluation submodule 11-1 processes the time domain signal collected by the first mode instability detection module 10-1 by performing a discrete Fourier transform on x(n), that is, Where X(k) is the frequency domain value, k is the sequence index of the frequency domain value; the frequency domain values ​​corresponding to the pump modulation frequency f and all its multiples are set to 0, that is, let X(k i )=0, where k i=mNf·ΔT+1, where m is an integer and ΔT is the sampling interval, and we get X'(k). We do inverse Fourier transform on X'(k) and get x'(n). Let I n = x'(n), and the same method as step (2) is used to calculate the corresponding mode instability threshold P under different time-domain modulation pump light source pump light modulation parameters. QCW =P th ;

[0079] (7) The performance evaluation submodule 11-1 sets the mode instability threshold P QCW Feedback is sent to the feedback control submodule 11-2, and steps (5)-(7) are repeated until the pump light modulation parameter group of the time domain modulated pump light source corresponding to the highest mode instability threshold is found, thereby obtaining a laser output with a higher mode instability threshold. out By P CW Growth to P QCW During the process, the laser output power continues to grow linearly, the time domain is stable, the frequency domain characteristic peaks are only the repetition frequency and its multiples corresponding to the pump modulation, and the mode instability phenomenon disappears.

[0080] Example 2

[0081] Reference Figure 2 The mode instability suppression device based on laser time domain regulation provided in Example 2 includes a fiber laser, a first mode instability detection module 10-1 and a control module 11, wherein the control module 11 includes a performance evaluation submodule 11-1, a feedback control submodule 11-2, and a pump control submodule 11-3, and the fiber laser includes a first pump signal combiner 1-1, a first fiber Bragg grating 1-2, a first gain fiber 1-3, a second fiber Bragg grating 1-4, a second pump signal combiner 1-5, a first cladding light filter 1-6, a first light Fiber end cap 1-7, second cladding light filter 1-8, second fiber end cap 1-9; one pump input arm of the first pump signal combiner 1-1 is connected to a first pump light source 2, and one pump input arm is connected to a second pump light source 4; one pump input arm of the second pump signal combiner 1-5 is connected to a third pump light source 6, and one pump input arm is connected to a fourth pump light source 8, wherein the first pump light source 2 and the third pump light source 6 are continuous pump light sources, and the second pump light source 4 and the fourth pump light source 8 are time-domain modulated pump light sources;

[0082] The pump output arm of the first pump signal combiner 1-1, the first fiber Bragg grating 1-2, the first gain fiber 1-3, the second fiber Bragg grating 1-4, and the pump output arm of the second pump signal combiner 1-5 are connected in sequence; the signal output arm of the second pump signal combiner 1-5, the first cladding optical filter 1-6, and the first fiber end cap 1-7 are connected in sequence; the signal output arm of the first pump signal combiner 1-1, the second cladding optical filter 1-8, and the second fiber end cap 1-9 are connected in sequence;

[0083] The first mode instability detection module 10-1 is used to detect the output characteristics of the laser output by the first optical fiber end cap 1-7 in real time, and transmit the detected information to the performance evaluation submodule 11-1;

[0084] The second mode instability detection module 10-2 is used to detect the output characteristics of the laser output from the second optical fiber end cap 1-9 in real time, and transmit the detected information to the performance evaluation submodule 11-1;

[0085] The performance evaluation submodule 11-1 determines the current state of the fiber laser and whether it reaches the mode instability threshold based on the information detected by the first mode instability detection module 10-1 and the second mode instability detection module 10-2;

[0086] The feedback control submodule 11-2 is configured to generate pump light modulation parameters based on a preloaded control algorithm according to the current state of the fiber laser and input the parameters to the pump control submodule 11-3. The pump control submodule 11-3 controls the current magnitude and timing characteristics of the driving power supplies of the first pump light source 2, the second pump light source 4, the third pump light source 6, and the fourth pump light source 8, thereby controlling the mode instability threshold. The positive and negative poles of the constant current output cable of the first pump light source driving power supply 3 are connected to the positive and negative poles of the power supply of the first pump light source 2; the positive and negative poles of the constant current output cable of the second pump light source driving power supply 5 are connected to the positive and negative poles of the power supply of the second pump light source 4; the positive and negative poles of the constant current output cable of the third pump light source driving power supply 7 are connected to the positive and negative poles of the power supply of the third pump light source 6; and the positive and negative poles of the constant current output cable of the fourth pump light source driving power supply 9 are connected to the positive and negative poles of the power supply of the fourth pump light source 8. Each driving power supply is configured to drive a corresponding pump light source to generate pump light output of corresponding intensity and timing. The control input ends of the first pump light source driving power supply 3, the second pump light source driving power supply 5, the third pump light source driving power supply 7 and the fourth pump light source driving power supply 9 are respectively connected to the output ends of the pump control submodule 11-3 of the control module 11, wherein the first pump light source 2 and the third pump light source 6 are continuous pump light sources, and the first pump light source driving power supply 3 and the third pump light source driving power supply 7 are continuous driving power supplies; the second pump light source 4 and the fourth pump light source 8 are time domain modulated pump light sources, and the second pump light source driving power supply 5 and the fourth pump light source driving power supply 9 are pulsed driving power supplies.

[0087] The following provides an embodiment 2 for implementing a mode instability suppression process based on laser time domain regulation. The pump control submodule 11-3 controls the current of the first pump light source driving power supply 3 and the third pump light source driving power supply 7 to continuously increase, corresponding to the continuous increase in the output power of the first pump light source 2 and the third pump light source 6. To improve system bandwidth and reduce costs, the first mode instability detection module 10-1 and the second mode instability detection module 10-2 use high-speed photodetectors to detect the time-frequency characteristics of the output laser and provide real-time feedback to the performance evaluation submodule 11-1. When the total pump power is 1711W and the total output power is 1390W, the first mode instability detection module 10-1 and the second mode instability detection module 10-2 both detect time-domain power fluctuations with a kHz characteristic frequency. At this time, the performance evaluation submodule 11-1 determines that the fiber laser has reached the mode instability threshold. Figure 6 , Figure 6 Schematic diagram of the laser output characteristic change of the mode instability suppression device based on laser time domain regulation provided in Example 2, wherein Figure 6 (a) is the graph showing the laser output power changing with pump power in the first stage. Figure 6(b) shows the time domain and frequency domain diagrams after mode instability occurs in the first stage. After mode instability occurs, if the pump power is continued to increase, the time domain power fluctuations will intensify, the frequency domain kHz characteristic peaks will increase and tend to be continuous, the laser output power will stagnate, and the mode instability will increase. At the power point corresponding to the mode instability threshold, the feedback control submodule 11-2 generates the pump light modulation parameters and inputs them to the pump control submodule 11-3, which controls the second pump light source driver power supply 5 and the fourth pump light source driver power supply 9, so that the second pump light source 4 and the fourth pump light source 8 output a square wave with a frequency of 1 kHz and a duty cycle of 10%. Figure 6 (c) and Figure 6 (d) Figure 6 (c) is the graph showing the variation of laser output power with pump power in the second stage. Figure 6 (d) shows the time and frequency domain diagrams after the second stage of mode instability is suppressed. After injecting the pulsed pump light sequence that has undergone time domain control, the laser output power continues to increase linearly, the time domain is stable, and the frequency domain only has the corresponding 1kHz repetition rate and its multiples after modulation, and the mode instability phenomenon disappears. The pump control submodule 11-3 continues to control the pulsed pump light power output by the second pump light source 4 and the fourth pump light source to increase to a maximum of 797W, and then continues to increase the continuous pump light power output by the first pump light source 2 and the third pump light source 6 to 1893W. The measured mode instability threshold of the fiber laser after adding time domain control is 2146W, which is 756W higher than the continuous pump mode.

[0088] Example 3

[0089] Reference Figure 3 The mode instability suppression device based on laser time domain control provided in Example 3 includes a fiber laser, a first mode instability detection module 10-1 and a control module 11, wherein the control module 11 includes a performance evaluation submodule 11-1, a feedback control submodule 11-2, and a pump control submodule 11-3. The fiber laser includes a first pump signal combiner 1-1, a first fiber Bragg grating 1-2, a first gain fiber 1-3, a second fiber Bragg grating 1-4, a second gain fiber 1-10, and a second pump signal combiner 1-5. , a first cladding light filter 1-6, and a first optical fiber end cap 1-7; a first pump light source 2 is connected to a pump input arm of the first pump signal combiner 1-1, and a second pump light source 4 is connected to a pump input arm; a third pump light source 6 is connected to a pump input arm of the second pump signal combiner 1-5, and a fourth pump light source 8 is connected to a pump input arm, wherein the first pump light source 2 and the third pump light source 6 are continuous pump light sources, and the second pump light source 4 and the fourth pump light source 8 are time-domain modulated pump light sources;

[0090] The pump output arm of the first pump signal combiner 1-1, the first fiber Bragg grating 1-2, the first gain fiber 1-3, the second fiber Bragg grating 1-4, the second gain fiber 1-10, and the pump output arm of the second pump signal combiner 1-5 are connected in sequence; the signal output arm of the second pump signal combiner 1-5, the first cladding light filter 1-6, and the first fiber end cap 1-7 are connected in sequence;

[0091] The first mode instability detection module 10-1 is used to detect the output characteristics of the laser output by the first optical fiber end cap 1-7 in real time, and transmit the detected information to the performance evaluation submodule 11-1;

[0092] The performance evaluation submodule 11-1 determines the current state of the fiber laser and whether it reaches the mode instability threshold based on the information detected by the first mode instability detection module 10-1;

[0093] The feedback control submodule 11-2 is configured to generate pump light modulation parameters based on a preloaded control algorithm according to the current state of the fiber laser and input the parameters to the pump control submodule 11-3. The pump control submodule 11-3 controls the current magnitude and timing characteristics of the driving power supplies of the first pump light source 2, the second pump light source 4, the third pump light source 6, and the fourth pump light source 8, thereby controlling the mode instability threshold. The positive and negative poles of the constant current output cable of the first pump light source driving power supply 3 are connected to the positive and negative poles of the power supply of the first pump light source 2; the positive and negative poles of the constant current output cable of the second pump light source driving power supply 5 are connected to the positive and negative poles of the power supply of the second pump light source 4; the positive and negative poles of the constant current output cable of the third pump light source driving power supply 7 are connected to the positive and negative poles of the power supply of the third pump light source 6; and the positive and negative poles of the constant current output cable of the fourth pump light source driving power supply 9 are connected to the positive and negative poles of the power supply of the fourth pump light source 8. Each driving power supply is configured to drive a corresponding pump light source to generate pump light output of corresponding intensity and timing. The control input ends of the first pump light source driving power supply 3, the second pump light source driving power supply 5, the third pump light source driving power supply 7 and the fourth pump light source driving power supply 9 are respectively connected to the output ends of the pump control submodule 11-3 of the control module 11, wherein the first pump light source 2 and the third pump light source 6 are continuous pump light sources, and the first pump light source driving power supply 3 and the third pump light source driving power supply 7 are continuous driving power supplies; the second pump light source 4 and the fourth pump light source 8 are time domain modulated pump light sources, and the second pump light source driving power supply 5 and the fourth pump light source driving power supply 9 are pulsed driving power supplies.

[0094] In Example 3, the mode instability suppression process based on laser time-domain control is implemented in the same manner as in Example 1, resulting in a laser output with a higher mode instability threshold. Example 3 differs from Example 1 in that if the output power of the first pump light source 2 and the second pump light source 4 is too low or zero, while the output power of the third pump light source 6 and / or the fourth pump light source 8 is not zero, this may threaten the stability and safety of the fiber laser output. This should be noted during implementation.

[0095] Example 4

[0096] Reference Figure 4 The mode instability suppression device based on laser time domain control provided in Example 4 includes a fiber laser, a first mode instability detection module 10-1 and a control module 11. The control module 11 includes a performance evaluation submodule 11-1, a feedback control submodule 11-2, and a pump control submodule 11-3.

[0097] The fiber laser includes a first pump signal combiner 1-1, a first fiber Bragg grating 1-2, a first gain fiber 1-3, a second fiber Bragg grating 1-4, a second cladding light filter 1-11, a second pump signal combiner 1-5, a second gain fiber 1-10, a third pump signal combiner 1-12, a first cladding light filter 1-6, and a first fiber end cap 1-7;

[0098] A first pump light source 2 is connected to one pump input arm of the first pump signal combiner 1-1, and a second pump light source 4 is connected to one pump input arm; a fourth pump light source 8 is connected to one pump input arm of the second pump signal combiner 1-5, and a third pump light source 6 is connected to one pump input arm of the third pump signal combiner 1-12, wherein the second pump light source 4 is a time-domain modulated pump light source, and the first pump light source 2, the third pump light source 6, and the fourth pump light source 8 are all continuous pump light sources;

[0099] The pump output arm of the first pump signal combiner 1-1, the first fiber Bragg grating 1-2, the first gain fiber 1-3, the second fiber Bragg grating 1-4, the second cladding optical filter 1-11, the signal output arm of the second pump signal combiner 1-5, the second gain fiber 1-10, and the pump output arm of the third pump signal combiner 1-12 are connected in sequence; the signal output arm of the third pump signal combiner 1-12, the first cladding optical filter 1-6, and the first fiber end cap 1-7 are connected in sequence;

[0100] The first mode instability detection module 10-1 is used to detect the output characteristics of the laser output by the first optical fiber end cap 1-7 in real time, and transmit the detected information to the performance evaluation submodule 11-1;

[0101] The performance evaluation submodule 11-1 determines the current state of the fiber laser and whether it reaches the mode instability threshold based on the information detected by the first mode instability detection module 10-1;

[0102] The feedback control submodule 11-2 is configured to generate pump light modulation parameters based on a preloaded control algorithm according to the current state of the fiber laser and input the parameters to the pump control submodule 11-3. The pump control submodule 11-3 controls the current magnitude and timing characteristics of the driving power supplies of the first continuous pump light source 2, the first time-domain modulation pump light source 4, the second continuous pump light source 6, and the second time-domain modulation pump light source 6, thereby controlling the mode instability threshold. The positive and negative poles of the constant current output cable of the first pump light source driving power supply 3 are connected to the positive and negative poles of the power supply of the first pump light source 2; the positive and negative poles of the constant current output cable of the second pump light source driving power supply 5 are connected to the positive and negative poles of the power supply of the second pump light source 4; the positive and negative poles of the constant current output cable of the third pump light source driving power supply 7 are connected to the positive and negative poles of the power supply of the third pump light source 6; and the positive and negative poles of the constant current output cable of the fourth pump light source driving power supply 9 are connected to the positive and negative poles of the power supply of the fourth pump light source 8. Each driving power supply is configured to drive a corresponding pump light source to generate pump light output of corresponding intensity and timing. The control input ends of the first pump light source driving power supply 3, the second pump light source driving power supply 5, the third pump light source driving power supply 7 and the fourth pump light source driving power supply 9 are respectively connected to the output ends of the pump control submodule 11-3 of the control module 11, wherein the first pump light source 2, the third pump light source 6 and the fourth pump light source 8 are all continuous pump light sources, and the first pump light source driving power supply 3, the third pump light source driving power supply 7 and the fourth pump light source driving power supply 9 are all continuous driving power supplies; the second pump light source 4 is a time domain modulated pump light source, and the second pump light source driving power supply 5 is a pulse driving power supply.

[0103] In Example 4, the mode instability suppression process based on laser time-domain control is implemented in the same manner as in Example 1, resulting in a laser output with a higher mode instability threshold. Unlike Example 1, in Example 4, if the output power of the first pump light source 2 is too low or zero, while the output power of the third pump light source 6 and / or the fourth pump light source 8 is not zero, this may threaten the stability and safety of the fiber laser output. This situation should be avoided during implementation.

[0104] Example 5

[0105] Reference Figure 5The mode instability suppression device based on laser time domain regulation provided in Example 5 includes a fiber laser, a first mode instability detection module 10-1 and a control module 11, wherein the control module 11 includes a performance evaluation submodule 11-1, a feedback control submodule 11-2, and a pump control submodule 11-3, and the fiber laser includes a first pump signal combiner 1-1, a first fiber grating 1-2, a first gain fiber 1-3, a second fiber grating 1-4, a second pump signal combiner 1-5, a first cladding light filter 1-6, a first fiber end cap 1-7, and a second cladding light filter. filter 1-8, a first phase modulator 1-13, a second phase modulator 1-14, and a polarization combiner 1-15; a first pump light source 2 is connected to one pump input arm of the first pump signal combiner 1-1, and a second pump light source 4 is connected to one pump input arm; a third pump light source 6 is connected to one pump input arm of the second pump signal combiner 1-5, and a fourth pump light source 8 is connected to one pump input arm, wherein the first pump light source 2 and the third pump light source 6 are continuous pump light sources, and the second pump light source 4 and the fourth pump light source 8 are time-domain modulated pump light sources;

[0106] The pump output arm of the first pump signal combiner 1-1, the first fiber Bragg grating 1-2, the first gain fiber 1-3, the second fiber Bragg grating 1-4, and the pump output arm of the second pump signal combiner 1-5 are connected in sequence; the signal output arm of the second pump signal combiner 1-5, the first cladding optical filter 1-6, and the input end of the second phase modulator 1-14 are connected in sequence; the signal output arm of the first pump signal combiner 1-1, the second cladding optical filter 1-8, and the input end of the first phase modulator 1-13 are connected in sequence; the output end of the first phase modulator 1-13 and the output end of the second phase modulator 1-14 are both connected to the polarization combiner 1-15, and the polarization combiner 1-15 is connected to the first fiber end cap 1-7;

[0107] The first mode instability detection module 10-1 is used to detect the output characteristics of the laser output by the first optical fiber end cap 1-7 in real time, and transmit the detected information to the performance evaluation submodule 11-1;

[0108] The second mode instability detection module 10-2 is used to detect the output characteristics of the laser output from the second optical fiber end cap 1-9 in real time, and transmit the detected information to the performance evaluation submodule 11-1;

[0109] The performance evaluation submodule 11-1 determines the current state of the fiber laser and whether it reaches the mode instability threshold based on the information detected by the first mode instability detection module 10-1 and the second mode instability detection module 10-2;

[0110] The feedback control submodule 11-2 is configured to generate pump light modulation parameters based on a preloaded control algorithm according to the current state of the fiber laser and input the parameters to the pump control submodule 11-3. The pump control submodule 11-3 controls the current magnitude and timing characteristics of the driving power supplies of the first pump light source 2, the second pump light source 4, the third pump light source 6, and the fourth pump light source 8, thereby controlling the mode instability threshold. The positive and negative poles of the constant current output cable of the first pump light source driving power supply 3 are connected to the positive and negative poles of the power supply of the first pump light source 2; the positive and negative poles of the constant current output cable of the second pump light source driving power supply 5 are connected to the positive and negative poles of the power supply of the second pump light source 4; the positive and negative poles of the constant current output cable of the third pump light source driving power supply 7 are connected to the positive and negative poles of the power supply of the third pump light source 6; and the positive and negative poles of the constant current output cable of the fourth pump light source driving power supply 9 are connected to the positive and negative poles of the power supply of the fourth pump light source 8. Each driving power supply is configured to drive a corresponding pump light source to generate pump light output of corresponding intensity and timing. The control input ends of the first pump light source driving power supply 3, the second pump light source driving power supply 5, the third pump light source driving power supply 7 and the fourth pump light source driving power supply 9 are respectively connected to the output ends of the pump control submodule 11-3 of the control module 11, wherein the first pump light source 2 and the third pump light source 6 are continuous pump light sources, and the first pump light source driving power supply 3 and the third pump light source driving power supply 7 are continuous driving power supplies; the second pump light source 4 and the fourth pump light source 8 are time domain modulated pump light sources, and the second pump light source driving power supply 5 and the fourth pump light source driving power supply 9 are pulsed driving power supplies.

[0111] In Example 5, the mode instability suppression process based on laser time-domain control is implemented in the same manner as in Example 1, thereby obtaining a laser output with a higher mode instability threshold. Example 5 differs from Example 1 in that the fiber laser utilizes polarization-maintaining fiber and components based on polarization-maintaining fiber, and the first fiber end cap 1-7 outputs linearly polarized light.

[0112] In any of the above embodiments:

[0113] The performance evaluation submodule 11-1 determines whether the current fiber laser has reached a mode unstable state based on the laser output characteristic change data detected by the mode instability detection module. If it is in a mode unstable state, the feedback control submodule 11-2 generates pump light modulation parameters (pump light control parameters include but are not limited to amplitude, frequency, duty cycle, waveform and modulation depth) according to the pre-loaded control algorithm and inputs them into the pump control submodule 11-3 to achieve control of the current size and timing characteristics of all pump light source drive power supplies. For each pulse drive power supply, different waveforms can also be set to drive, thereby achieving control of the mode instability threshold. The pre-loaded control algorithm running in the feedback control submodule 11-2 is not limited and can be linear or nonlinear, including but not limited to various optimization algorithms such as stochastic parallel gradient descent algorithm, hill climbing method, genetic algorithm, simulated annealing algorithm, ant colony algorithm, auto-disturbance rejection control, PID control, fuzzy control, neural network control, etc.

[0114] The mode instability detection module described in each of the above embodiments is used to detect changes in laser output characteristics caused by mode instability, and input the changes into the performance evaluation submodule 11-1 for analysis and processing. The output laser characteristics detected by the mode instability detection module include but are not limited to: power, time domain, mode ratio, beam quality, etc. Common changes in laser characteristics after the occurrence of mode instability include: time domain power fluctuations with kHz characteristic frequency, laser power stagnation or decline, laser mode dynamic coupling, rapid decline in beam quality, etc. The detection means of mode instability include but are not limited to: high-speed photodetectors, high-speed cameras, beam quality analyzers, etc. The performance evaluation submodule 11-1 determines whether the fiber laser has mode instability based on the laser output characteristic change data detected by the mode instability detection module.

[0115] In each of the above-described embodiments, the pulsed pump light sequence output by the time-domain modulated pump light source, which has undergone time-domain regulation, can be periodic or aperiodic, and its regulation parameters include, but are not limited to, amplitude, frequency, duty cycle, waveform, and modulation depth, and are controlled and adjusted by the pump control submodule 11-3. When the pump control submodule 11-3 regulates the pulsed drive power supply corresponding to the time-domain modulated pump light source, its direct modulation signal can be generated by a voltage-controlled oscillator, a radio frequency signal generator, a waveform generator, or other electronic modulation device to achieve precise control of the pulsed pump light sequence. The direct modulation signal can be digital or analog.

[0116] The gain fiber used in the above embodiments is a rare earth ion doped fiber (Er 3+ / Yb 3+Single-clad, double-clad, triple-clad, or special multi-clad optical fibers (e.g., optical fibers with uniform dimensions, tapered fibers, or fibers with optimized transverse structures, such as limited-doping fibers) can be used. The core and cladding can be configured in any geometric shape. Under certain conditions, the gain fiber can support transmission in two or more modes.

[0117] In each of the above embodiments, the first pump light source 2, the second pump light source 4, the third pump light source 6, and the fourth pump light source 8 are all fiber-coupled semiconductor lasers, including stabilized and non-stabilized wavelength types, with a central wavelength range of 910 to 1020 nm. The pump signal combiners include side-pumped and end-pumped combiners.

[0118] In the above embodiments, the core and cladding diameters of the first fiber Bragg grating 1-2 and the second fiber Bragg grating 1-4 match the core and cladding diameters of the gain fiber between the first fiber Bragg grating 1-2 and the second fiber Bragg grating 1-4, the central wavelength range of the first fiber Bragg grating 1-2 and the second fiber Bragg grating 1-4 is 1000nm to 1200nm, the grating reflectivity range is 1% to 100%, the central wavelengths of the first fiber Bragg grating 1-2 and the second fiber Bragg grating 1-4 match, and the reflectivity can be arbitrarily matched within an optional range.

[0119] By integrating an electrical subsystem, namely a control module 11, into an existing fiber laser system, the present invention can achieve time-domain control of the laser without destroying the optical structure of the fiber laser, thereby suppressing the mode instability effect. This method can be further combined with other mode instability suppression technologies, including thermal management technology, beam shaping technology, mode selection technology, etc., to further enhance the suppression effect of mode instability.

[0120] Matters not covered by the present invention are known technologies.

[0121] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements are intended to fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

[0123] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for suppressing mode instability based on laser time-domain control, characterized in that: The fiber laser includes one or more continuous pump light sources and one or more time-domain modulated pump light sources. The time-domain modulated pump light sources are used to output a pulsed pump light sequence that has been time-domain modulated. By detecting the output characteristics of the fiber laser, the current state of the fiber laser and whether the mode instability threshold has been reached are determined. If the mode instability threshold has been reached, the pulsed pump light sequence that has been time-domain modulated is injected into the fiber laser. The pump light modulation parameters of each time-domain modulated pump light source are continuously changed based on a control algorithm. The pump light modulation parameters of the time-domain modulated pump light source include the amplitude, frequency, duty cycle, waveform and / or modulation depth of the pulsed pump light sequence. The output characteristics of the fiber laser are synchronously detected until it is detected that the laser output power of the fiber laser continues to increase linearly, the time domain is stable, the frequency domain characteristic peaks only have the repetition frequency and its multiple frequency corresponding to the pump modulation, and the mode instability phenomenon disappears. In this way, the mode instability effect in the fiber laser is effectively suppressed, and the output power of the fiber laser is further improved.

2. The method for suppressing mode instability based on laser time domain control according to claim 1, characterized in that: The fiber laser comprises a first pump signal combiner (1-1), a first fiber Bragg grating (1-2), a first gain fiber (1-3), a second fiber Bragg grating (1-4), a second pump signal combiner (1-5), a first cladding light filter (1-6), and a first fiber end cap (1-7); a first pump light source (2) is connected to a pump input arm of the first pump signal combiner (1-1), and a second pump light source (4) is connected to a pump input arm; a third pump light source (6) is connected to a pump input arm of the second pump signal combiner (1-5), and a fourth pump light source (8) is connected to a pump input arm, wherein the first pump light source (2) and the third pump light source (6) are continuous pump light sources, and the second pump light source (4) and the fourth pump light source (8) are time-domain modulated pump light sources; The pump output arm of the first pump signal combiner (1-1), the first fiber Bragg grating (1-2), the first gain fiber (1-3), the second fiber Bragg grating (1-4), and the pump output arm of the second pump signal combiner (1-5) are connected in sequence; the signal output arm of the second pump signal combiner (1-5), the first cladding light filter (1-6), and the first fiber end cap (1-7) are connected in sequence; the first fiber end cap (1-7) serves as the output end of the fiber laser and finally outputs laser light.

3. The method for suppressing mode instability based on laser time domain control according to claim 1, characterized in that: The fiber laser comprises a first pump signal combiner (1-1), a first fiber grating (1-2), a first gain fiber (1-3), a second fiber grating (1-4), a second pump signal combiner (1-5), a first cladding light filter (1-6), a first fiber end cap (1-7), a second cladding light filter (1-8), and a second fiber end cap (1-9); a first pump light source (2) is connected to a pump input arm of the first pump signal combiner (1-1), and a second pump light source (2) is connected to a pump input arm of the first pump signal combiner (1-1). A second pump light source (4) is connected to a pump input arm; a third pump light source (6) is connected to a pump input arm of the second pump signal combiner (1-5), and a fourth pump light source (8) is connected to a pump input arm, wherein the first pump light source (2) and the third pump light source (6) are continuous pump light sources, and the second pump light source (4) and the fourth pump light source (8) are time-domain modulated pump light sources, and the time-domain modulated pump light source is used to output a pulsed pump light sequence for time-domain regulation; The pump output arm of the first pump signal combiner (1-1), the first fiber Bragg grating (1-2), the first gain fiber (1-3), the second fiber Bragg grating (1-4), and the pump output arm of the second pump signal combiner (1-5) are connected in sequence; the signal output arm of the second pump signal combiner (1-5), the first cladding optical filter (1-6), and the first fiber end cap (1-7) are connected in sequence; the signal output arm of the first pump signal combiner (1-1), the second cladding optical filter (1-8), and the second fiber end cap (1-9) are connected in sequence; the first fiber end cap (1-7) and the second fiber end cap (1-9) serve as two output ends of a fiber laser, and ultimately output laser light.

4. The method for suppressing mode instability based on laser time domain control according to claim 1, characterized in that: The fiber laser comprises a first pump signal combiner (1-1), a first fiber Bragg grating (1-2), a first gain fiber (1-3), a second fiber Bragg grating (1-4), a second gain fiber (1-10), a second pump signal combiner (1-5), a first cladding light filter (1-6), and a first fiber end cap (1-7); a first pump light source (2) is connected to a pump input arm of the first pump signal combiner (1-1), and a second pump light source (4) is connected to a pump input arm; a third pump light source (6) is connected to a pump input arm of the second pump signal combiner (1-5), and a fourth pump light source (8) is connected to a pump input arm, wherein the first pump light source (2) and the third pump light source (6) are continuous pump light sources, and the second pump light source (4) and the fourth pump light source (8) are time-domain modulated pump light sources; The pump output arm of the first pump signal combiner (1-1), the first fiber Bragg grating (1-2), the first gain fiber (1-3), the second fiber Bragg grating (1-4), the second gain fiber (1-10), and the pump output arm of the second pump signal combiner (1-5) are connected in sequence; the signal output arm of the second pump signal combiner (1-5), the first cladding light filter (1-6), and the first fiber end cap (1-7) are connected in sequence; the first fiber end cap (1-7) serves as the output end of the fiber laser and finally outputs laser light.

5. The method for suppressing mode instability based on laser time domain control according to claim 1, characterized in that: The fiber laser comprises a first pump signal combiner (1-1), a first fiber grating (1-2), a first gain fiber (1-3), a second fiber grating (1-4), a second cladding optical filter (1-11), a second pump signal combiner (1-5), a second gain fiber (1-10), a third pump signal combiner (1-12), a first cladding optical filter (1-6), and a first fiber end cap (1-7); A first pump light source (2) is connected to a pump input arm of the first pump signal combiner (1-1), and a second pump light source (4) is connected to a pump input arm of the second pump signal combiner (1-5); a fourth pump light source (8) is connected to a pump input arm of the second pump signal combiner (1-5); and a third pump light source (6) is connected to a pump input arm of the third pump signal combiner (1-12), wherein the second pump light source (4) is a time-domain modulated pump light source, and the first pump light source (2), the third pump light source (6), and the fourth pump light source (8) are all continuous pump light sources. The pump output arm of the first pump signal combiner (1-1), the first fiber Bragg grating (1-2), the first gain fiber (1-3), the second fiber Bragg grating (1-4), the second cladding optical filter (1-11), the signal output arm of the second pump signal combiner (1-5), the second gain fiber (1-10), and the pump output arm of the third pump signal combiner (1-12) are connected in sequence; the signal output arm of the third pump signal combiner (1-12), the first cladding optical filter (1-6), and the first fiber end cap (1-7) are connected in sequence; the first fiber end cap (1-7) serves as the output end of the fiber laser and finally outputs laser light.

6. The method for suppressing mode instability based on laser time domain control according to claim 1, characterized in that: The fiber laser comprises a first pump signal combiner (1-1), a first fiber grating (1-2), a first gain fiber (1-3), a second fiber grating (1-4), a second pump signal combiner (1-5), a first cladding light filter (1-6), a first fiber end cap (1-7), a second cladding light filter (1-8), a first phase modulator (1-13), a second phase modulator (1-14), and a polarization combiner (1-15); the first pump signal combiner A first pump light source (2) is connected to a pump input arm of the device (1-1), and a second pump light source (4) is connected to a pump input arm; a third pump light source (6) is connected to a pump input arm of the second pump signal combiner (1-5), and a fourth pump light source (8) is connected to a pump input arm, wherein the first pump light source (2) and the third pump light source (6) are continuous pump light sources, and the second pump light source (4) and the fourth pump light source (8) are time-domain modulated pump light sources; The pump output arm of the first pump signal combiner (1-1), the first fiber Bragg grating (1-2), the first gain fiber (1-3), the second fiber Bragg grating (1-4), and the pump output arm of the second pump signal combiner (1-5) are connected in sequence; the signal output arm of the second pump signal combiner (1-5), the first cladding optical filter (1-6), and the input end of the second phase modulator (1-14) are connected in sequence; the signal output arm of the first pump signal combiner (1-1), the second cladding optical filter (1-8), and the input end of the first phase modulator (1-13) are connected in sequence; the output end of the first phase modulator (1-13) and the output end of the second phase modulator (1-14) are both connected to the polarization combiner (1-15); the polarization combiner (1-15) is connected to the first fiber end cap (1-7); the first fiber end cap (1-7) serves as the output end of the fiber laser and ultimately outputs laser light.

7. The method for suppressing mode instability based on laser time domain control according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) The current of the driving power supply of each continuous pump light source in the fiber laser is continuously increased, and the output power of the corresponding continuous pump light source is continuously increased. out The time domain signal of the output laser is collected, and the signal intensity corresponding to the nth time series sampling point is I n , where n = 1, 2, 3, ..., N; (2) Determine the mode instability threshold: calculate the mean value of the signal strength Normalized standard deviation According to the formula σ norm (P out )=A·exp(B·P out )+C, where A, B, and C are all constants, and the normalized standard deviation curve σ is obtained by fitting with the output power norm (P out ); let σ norm (P out ) is equal to 0.1‰ / W, which satisfies the threshold judgment condition Where W represents the unit, which means watt; the solution is to obtain the mode instability threshold P CW =P th , P th Indicates that the threshold judgment condition is met P out ; (3) When P is detected out =P CW When the current of the driving power supply of each continuous pump light source is stopped, the P out =P CW The current value of the driving power supply of each continuous pump light source remains unchanged; (4) setting an initial value of a pump light modulation parameter controlling each time-domain modulated pump light source so that each time-domain modulated pump light source outputs a pulsed pump light sequence corresponding to the pump light modulation parameter; (5) In order to find the optimal pump light modulation parameters of the time domain modulated pump light source, the pump light modulation parameters of each time domain modulated pump light source are continuously changed according to the pre-set control algorithm, and the different output powers P corresponding to the pump light modulation parameters of different time domain modulated pump light sources are collected. out The time domain signal of the output laser is x(n), and the signal intensity corresponding to the nth time series sampling point is x(n), where n = 1, 2, 3, ..., N; (6) Perform discrete Fourier transform on x(n), that is, Where X(k) is the frequency domain value, k is the sequence index of the frequency domain value; the frequency domain values ​​corresponding to the pump modulation frequency f and all its multiples are set to 0, that is, let X(k i )=0, where k i =mNf·ΔT+1, where m is an integer and ΔT is the sampling interval, and we get X'(k). We do inverse Fourier transform on X'(k) and get x'(n). Let I n = x'(n), and the same method as step (2) is used to calculate the corresponding mode instability threshold P under different time-domain modulation pump light source pump light modulation parameters. QCW =P th ; (7) Repeat steps (5)-(7) until the pump light modulation parameters of the time-domain modulated pump light source corresponding to the highest mode instability threshold are found, thereby obtaining a laser output with a higher mode instability threshold. out By P CW Growth to P QCW During the process, the laser output power continues to grow linearly, the time domain is stable, the frequency domain characteristic peaks are only the repetition frequency and its multiples corresponding to the pump modulation, and the mode instability phenomenon disappears.

8. A mode instability suppression device based on laser time domain control, characterized in that: It includes a fiber laser, a mode instability detection module, and a control module; The fiber laser includes one or more continuous pump light sources and one or more time-domain modulated pump light sources, wherein the time-domain modulated pump light sources are used to output a pulsed pump light sequence that has been time-domain regulated; The mode instability detection module is used to detect the output characteristics of the fiber laser in real time; The control module determines the current state of the fiber laser and whether the mode instability threshold is reached based on the detected output characteristics. If the mode instability threshold is reached, a pulsed pump light sequence that has been time-domain modulated is injected into the fiber laser, and the pump light modulation parameters of each time-domain modulated pump light source are continuously changed based on the control algorithm. The pump light modulation parameters of the time-domain modulated pump light source include the amplitude, frequency, duty cycle, waveform and / or modulation depth of the pulsed pump light sequence. The output characteristics of the fiber laser are synchronously detected until it is detected that the laser output power of the fiber laser continues to increase linearly, the time domain is stable, the frequency domain characteristic peaks only have the repetition frequency and its multiple frequency corresponding to the pump modulation, and the mode instability phenomenon disappears. In this way, the mode instability effect in the fiber laser is effectively suppressed, and the output power of the fiber laser is further improved.

9. The mode instability suppression device based on laser time domain control according to claim 8, characterized in that: The fiber laser includes a fiber laser oscillator, a fiber laser amplifier, an oscillation-amplification integrated fiber laser, and a fiber laser with a single-end output or double-end output structure.

10. The mode instability suppression device based on laser time domain control according to claim 8 or 9, characterized in that: The mode instability detection module is used to detect the laser output characteristics caused by mode instability in real time. The output laser characteristics detected by the mode instability detection module include but are not limited to: power, time domain, mode ratio, and beam quality; The control module includes a performance evaluation submodule, a feedback control submodule, and a pump control submodule. The output laser characteristics detected by the mode instability detection module are input into the performance evaluation submodule for analysis and processing. The performance evaluation submodule determines the current state of the fiber laser and whether the mode instability threshold is reached and mode instability occurs based on the laser output characteristic change data detected by the mode instability detection module. The laser characteristic changes after the current fiber laser reaches the mode instability threshold and mode instability occurs include: time domain power fluctuations with a kHz characteristic frequency, laser power stagnation or decline, laser mode dynamic coupling, and rapid decline in beam quality. When the performance evaluation submodule determines that the current fiber laser has reached a mode instability threshold and mode instability occurs, the control algorithm run by the feedback control submodule continuously changes the pump light modulation parameters of each time-domain modulated pump light source and transmits them to the pump control submodule, so that each time-domain modulated pump light source injects a pulsed pump light sequence that has been time-domain controlled into the fiber laser, wherein the control algorithm run in the feedback control submodule is linear or nonlinear, including but not limited to: random parallel gradient descent algorithm, hill climbing method, genetic algorithm, simulated annealing algorithm, ant colony algorithm, auto-disturbance rejection control algorithm, PID control algorithm, fuzzy control algorithm, and neural network control algorithm.

Images