A laser pulse waveform regulation system based on incoherent combination and adjustable beam splitting

Abstract

This invention provides a laser pulse waveform control system based on incoherent combining and tunable beam splitting, mainly composed of a broadband pulse seed source, a first module, a second module, and a reflective fiber grating. The pulsed laser signal output from the broadband pulse seed source is first amplified by the first module, and then split into two beams by a tunable beam splitter: one beam is reflected by the first module and the reflective fiber grating to the third port of a circulator for subsequent amplification; the other beam enters the second module for pulse delay and gain amplification, and then is reinjected into the first module through a loop to achieve secondary amplification and cyclic beam splitting. The system relies on the reflective fiber grating and the loop optical path to delay, amplify, and combine time-domain pulses, outputting a tunable laser signal at the third port of the circulator. This scheme is a highly stable, all-fiber integrated pulse time-domain shaping method compatible with MOPA systems, which can effectively improve the processing adaptability and application range of laser processing systems.

Description

Technical Field

[0001] This invention relates to the field of fiber laser technology, and in particular to a laser pulse waveform control system based on incoherent combining and tunable beam splitting. Background Technology

[0002] Fiber lasers are widely used in industrial processing, military defense, and other fields due to their excellent beam quality, high conversion efficiency, and compactness. Nanosecond pulsed lasers with MOPA (Master Oscillator Power Amplifier) ​​structure have been widely used in industrial fields such as marking, cutting, welding, and drilling due to their high peak power and high beam quality.

[0003] The output pulse shape of existing industrial MOPA pulsed fiber lasers suffers from waveform distortion during gain amplification due to gain saturation, resulting in an excessively high pulse leading edge and an excessively low trailing edge. Furthermore, different processing scenarios typically require laser pulses with specific temporal energy distributions to achieve better processing quality and efficiency. Existing pulse shaping methods based on interference or nonlinear effects face challenges in industrial environments, including poor stability, complex adjustment, and high costs. Particularly for nanosecond-level pulses, achieving highly stable, real-time programmable temporal waveform control without introducing additional noise is difficult.

[0004] Therefore, the ability to flexibly and controllably adjust the time-domain waveform of the output pulse of a fiber laser has become a key technical requirement for improving the performance of laser processing systems and expanding their application areas. Summary of the Invention

[0005] To address the aforementioned deficiencies and improvement needs of existing technologies, this invention provides a laser pulse waveform control system based on incoherent combining and tunable beam splitting. Its purpose is to provide a stable, flexible, and fully fiber-integrated time-domain pulse shaping laser amplifier. This invention outputs a pulsed laser signal from a broadband pulse seed source. Using two beams split by a tunable beam splitter, the pulsed laser signal is split, delayed, amplified, combined, and re-amplified based on a first module, a second module, and a reflective fiber grating. Ultimately, this achieves a flexibly tunable pulsed laser output that is injected into the subsequent main amplification stage.

[0006] To solve the above technical problems, the present invention provides a laser pulse waveform control system based on incoherent combining and tunable beam splitting, including a broadband pulse seed source, a first module, a second module and a reflective fiber grating. The broadband pulse seed source, the first module and the reflective fiber grating are sequentially optically connected along the signal transmission direction. The second module and the first module are optically connected to each other to form a closed loop optical path. The first module amplifies and splits the pulsed laser signal output from the broadband pulse seed source to obtain a first split beam and a second split beam. The reflective fiber grating is used to reflect the first split beam back to the first module and output it. The second module delays and amplifies the second split beam and feeds the amplified second split beam back to the first module to achieve incoherent synthesis of the first and second split beams, thereby realizing tunable control of the laser pulse waveform.

[0007] Preferably, the first module includes a signal laser beam combiner, a first pump unit, a circulator, and an adjustable beam splitter; The signal laser beam combiner has its first input connected to a broadband pulse seed source, its second input connected to the output of the second module, and its output connected to the input of the first pump unit. The output of the first pump unit is connected to the first port of the circulator. The second port of the circulator is connected to the input of the adjustable beam splitter, and its third port is connected to the subsequent amplification stage. The circulator allows the signal laser to travel from the first port to the second port and from the second port to the third port. The first output of the adjustable beam splitter is connected to a reflective fiber grating, and its second output is connected to the input of the second module.

[0008] Preferably, the first pump unit includes a first gain fiber, a first pump combiner, and a first pump source; the first end of the first gain fiber is fused to the output end of the signal laser combiner, and the second end is fused to the input end of the first pump combiner; the pump end of the first pump combiner is optically connected to the first pump source, and the output end is optically connected to the first port of the circulator.

[0009] Preferably, the second module includes a passive optical fiber and a second pump unit. The first end of the passive optical fiber is fused to the second output end of the adjustable beam splitter, and the second end is fused to the input end of the second pump unit. The output end of the second pump unit is optically connected to the second input end of the signal laser beam combiner.

[0010] Preferably, when the second beam passes through the passive optical fiber, it generates an optical path difference and forms a time-domain delay of one pulse width; the leading edge of the pulse after the time-domain delay completely coincides with the trailing edge of the pulse signal laser output by the broadband pulse seed source, and the optical path difference is greater than the coherence length between the first beam and the second beam.

[0011] Preferably, the second pump unit includes a second gain fiber, a second pump combiner, and a second pump source; the first end of the second gain fiber is fused to the second end of the passive fiber, and the second end is fused to the input end of the second pump combiner; the pump end of the second pump combiner is optically connected to the second pump source, and the output end is optically connected to the second input end of the signal laser combiner.

[0012] Preferably, the core diameter of the pigtail fiber of any one of the pump arm of the first pump combiner, the pump arm of the second pump combiner, the first pump source, and the second pump source is 105 μm, and the inner cladding diameter is 125 μm.

[0013] Preferably, both the first gain fiber and the second gain fiber are double-clad ytterbium-doped gain fibers; the core diameter of the double-clad ytterbium-doped gain fiber is 10 μm, and the inner cladding diameter is 130 μm; the refractive index of the outer cladding of the double-clad ytterbium-doped gain fiber is lower than that of the inner cladding, and the refractive index of the inner cladding is lower than that of the core; both the first pump source and the second pump source are semiconductor lasers with an output wavelength in the range of 915 nm to 1018 nm.

[0014] Preferably, the reflective fiber grating is a high-power chirped fiber grating with the same center wavelength as the broadband pulse seed source, a 3dB bandwidth of 8nm, and a reflectivity of not less than 99.5%. The pigtail on the side of the reflective fiber grating away from the tunable splitter has a beveled structure, and the end of the pigtail is provided with a curing layer, the refractive index of which is lower than that of the pigtail.

[0015] Preferably, the spectral width of the broadband pulse seed source is greater than 10 nm; the output signal pigtail of the broadband pulse seed source is a polarization-maintaining fiber with a core diameter of 6 μm and an inner cladding diameter of 125 μm; the pulse signal laser is linearly polarized light and propagates along the fast axis of the polarization-maintaining fiber.

[0016] Beneficial Effects: This invention employs a closed-loop optical path design combining a broadband pulse seed source with incoherent synthesis and adjustable beam splitting. The second module precisely delays and amplifies the second beam in the time domain, then feeds it back to the first module to achieve stable incoherent intensity superposition with the first beam reflected by a reflective fiber grating. The pulse time-domain energy distribution can be precisely controlled by flexibly adjusting the beam splitting ratio and amplification power. This fundamentally solves the shortcomings of traditional interferometric pulse shaping methods, such as phase sensitivity, poor stability, complex adjustment, and high cost. It also effectively suppresses waveform distortion caused by gain saturation in MOPA-structured pulsed fiber lasers, resulting in excessively high pulse leading edges and low trailing edges. Furthermore, it features all-fiber integration, high stability, no additional noise, and high compatibility with MOPA systems. It can output flexibly adjustable pulse waveforms as needed, significantly improving the processing adaptability, processing quality, and working efficiency of laser processing systems, and expanding the application scope of fiber lasers in industrial processing. Attached Figure Description

[0017] Figure 1 This is an optical path structure diagram of the laser pulse waveform control system based on incoherent combining and tunable beam splitting provided by the present invention; Figure 2 This is a schematic diagram of time-domain pulse waveform modulation provided in Example 1; In the attached figures: 11-Broadband pulse seed source; 12-Signal laser combiner; 13-First gain fiber; 14-First pump combiner; 15-First pump source; 16-Circulator; 17-Adjustable beam splitter; 18-Reflective fiber grating; 19-Passive fiber; 20-Second gain fiber; 21-Second pump combiner; 22-Second pump source; 101-Time-domain waveform output from broadband pulse seed source 11; 102-Time-domain waveform after delay by passive fiber 19 in the second module; 103-Incoherent intensity synthesis in the time domain of the signal laser after delay by passive fiber 19 and the signal laser output from broadband pulse seed source 11 in the second module; 104-Incoherent intensity synthesis in the time domain of the signal laser after delay and gain amplification and the signal laser output from broadband pulse seed source 11 in the second module; 105-Time-domain pulse waveform finally output at port 3 of circulator 16 after adjustment. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] To address the shortcomings of existing technologies, the key to this invention lies in employing a broadband pulse seed source with a spectral width greater than 10 nm, and combining it with a delayed passive fiber to introduce an optical path difference far exceeding the coherence length of the seed source. This causes the two pulses in the signal laser beam combiner to lose coherence, achieving only stable superposition of incoherent intensities. This fundamentally solves the problem of output instability caused by phase sensitivity in traditional interferometric shaping methods. Furthermore, by adjusting the beam splitting ratio of the adjustable beam splitter, the energy ratio of the two pulses can be linearly and stably controlled, enabling flexible adjustment of the output pulse's time-domain waveform. Overall, this invention utilizes an adjustable beam splitter to split the laser beam. The first and second modules complete the beam splitting, delay, gain amplification, beam combining, and re-amplification processes, outputting a pulsed laser with an adjustable waveform to the subsequent main amplification stage. Through pulse pre-shaping, it effectively suppresses waveform distortion caused by gain saturation in MOPA structure pulsed fiber lasers, resulting in excessively high pulse leading edges and excessively low trailing edges.

[0020] Please see Figure 1 The laser pulse waveform control system based on incoherent synthesis and tunable beam splitting provided by the present invention includes a broadband pulse seed source 11, a first module, a second module and a reflective fiber grating 18. The broadband pulse seed source 11, the first module and the reflective fiber grating 18 are optically connected sequentially along the signal transmission direction. The second module and the first module are optically connected to each other to form a closed loop optical path. In this system, a broadband pulse seed source 11 outputs a pulse signal laser and injects it into a first module. The first module amplifies and splits the pulse signal laser to obtain a first split beam and a second split beam. A reflective fiber grating 18 is used to reflect the first split beam back to the first module and output it. The second module delays and amplifies the second split beam and feeds the amplified second split beam back to the first module to achieve incoherent synthesis of the first and second split beams, thereby realizing tunable control of the laser pulse waveform.

[0021] In this embodiment of the invention, the first module includes a signal laser beam combiner 12, a first pump unit, a circulator 16, and an adjustable beam splitter 17. The first pump unit includes a first gain fiber 13, a first pump beam combiner 14, and a first pump source 15. The two pigtails at the input end of the signal laser beam combiner 12 are respectively connected to the broadband pulse seed source 11 and the output signal pigtail of the second pump beam combiner 21. The output pigtail is connected to the first gain fiber 13, and the other side of the first gain fiber 13 is connected to the first pump beam combiner 16. 4. The input signal pigtail is connected; the pump pigtail of the first pump combiner 14 is connected to the first pump source 15, the output signal pigtail is connected to port 1 of the circulator 16, port 2 of the circulator 16 is connected to the input pigtail of the adjustable beam splitter 17, and the two output pigtails of the adjustable beam splitter 17 are connected to the input pigtail of the reflective fiber grating 18 and the passive fiber 19, respectively; the pulse signal laser is amplified and split in the first module to form the first beam beam, which is finally reflected to port 3 of the circulator 16 to enter the subsequent amplification stage.

[0022] In this embodiment of the invention, the second module includes a passive optical fiber 19 and a second pump unit. The second pump unit includes a second gain optical fiber 20, a second pump combiner 21, and a second pump source 22. The passive optical fiber 19 is connected to the adjustable beam splitter 17 and the second gain optical fiber 20 on both sides, and the other side of the second gain optical fiber 20 is connected to the input signal pigtail of the second pump combiner 21. The pump pigtail of the second pump combiner 21 is connected to the second pump source 22, and the output signal pigtail is connected to the signal laser combiner 12. The other pulsed signal laser beam (the second split beam) split by the adjustable beam splitter 17 is amplified by gain after passing through an additional optical path difference in the second ring optical path and finally returns to the first module.

[0023] In this embodiment of the invention, the spectral width of the broadband pulse seed source 11 is greater than 10 nm, and the diameter of the output signal tail fiber core / inner cladding is 6 / 125 μm. The above design can not only significantly shorten the laser coherence length and ensure that the two pulses achieve stable incoherent intensity superposition, thus avoiding the phase sensitivity and output instability problems of traditional interferometric shaping, but also match the core size of the subsequent all-fiber optical path, improving the optical path coupling efficiency and system integration stability.

[0024] In this embodiment of the invention, the signal laser beam combiner 12 has a reverse backlight isolation function, which can effectively block the optical signal transmitted in the opposite direction, protect the broadband pulse seed source 11 and the second module from backlight interference and damage, and improve the system's working stability and device reliability.

[0025] Specifically, in the pump arms of the first pump combiner 14 and the second pump combiner 21, as well as the first pump source 15 and the second pump source 22, the pigtail size is 105 / 125μm, while the pigtails and passive optical fibers of all other devices are 10 / 130μm in size. The above design can achieve efficient coupling of pump light and low-loss transmission of signal light, thereby improving the system's optical path compatibility, integration, and operational stability.

[0026] In this embodiment of the invention, the first gain fiber 13 and the second gain fiber 20 are double-clad ytterbium-doped gain fibers with core / inner cladding diameters of 10 / 130 μm. The refractive index of the outer cladding is lower than that of the inner cladding, and then lower than that of the core. The above design can ensure efficient transmission and absorption of pump light in the cladding and stable transmission of signal light in the core with low loss, and can also improve the optical field confinement capability and gain efficiency.

[0027] In this embodiment of the invention, a semiconductor laser with an output wavelength in the range of 915-1018nm is used. This wavelength band is highly matched with the absorption peak of double-clad ytterbium-doped gain fiber, which can significantly improve the pump light absorption efficiency and energy conversion efficiency, and ensure that the system has sufficient gain and stable output during pulse amplification.

[0028] In this embodiment of the invention, the circulator 16 adopts a three-port unidirectional transmission structure, with the signal laser transmitted directionally from port 1 to port 2 and from port 2 to port 3. It also has a reverse optical isolation function, which can effectively block the interference and feedback of the reverse transmitted light, ensure the stable operation of the optical path in one direction, protect the front-end devices, and ensure the reliable execution of the pulse waveform modulation and amplification process.

[0029] In this embodiment of the invention, the adjustable beam splitter 17 splits the input signal laser into two beams. The splitting ratio can be freely adjusted by rotating the lever on the beam splitter. One laser beam (the second split beam) is injected into the second module, and the other laser beam (the first split beam) is injected into the reflective fiber grating 18. In this embodiment of the invention, the reflective fiber grating 18 is a high-power chirped fiber grating with the same center wavelength as the broadband pulse seed source 11, a 3dB bandwidth of 8nm, and a reflectivity ≥99.5%. One of its pigtails is connected to the adjustable beam splitter 17, and the other pigtail is treated with a slanted angle and low-reflection curing. The above design can achieve efficient, broadband, and stable reflection output of signal light. Combined with the slanted angle and low-reflection curing treatment of the pigtail, it can effectively suppress end-face feedback and echo interference, ensuring stable operation of the system under high-power conditions.

[0030] In this embodiment of the invention, when the signal laser passes through, an optical path difference is applied, causing a time-domain delay. This optical path difference is much greater than the coherence length between the two signal laser beams separated by the adjustable beam splitter 17, thereby ensuring that the two beams only have intensity superposition after being combined by the signal laser beam combiner 12.

[0031] In this embodiment of the invention, the signal laser combiner 12 combines the signal laser output from the broadband pulse seed source 11 and the second module. After the signal laser is amplified by the reverse pump structure (first pump unit), it is injected from port 1 to port 2 of the circulator 16, then reflected by the reflective fiber grating 18, and finally output from port 3 of the circulator 16 and injected into the subsequent amplification stage.

[0032] In this embodiment of the invention, the pulsed signal laser injected into the second module is subjected to an additional optical path difference after passing through the passive optical fiber 19, resulting in a time delay of exactly one pulse width. The leading edge of the pulse in the time domain completely coincides with the trailing edge of the signal laser pulse output by the broadband pulse seed source 11. The two signal lasers are combined at the signal laser combiner 12 and injected into the first module for gain amplification.

[0033] In this embodiment of the invention, by adjusting the splitting ratio of the adjustable beam splitter 17 and the pump power of the second pump source 22 in the second module, the pulse signal laser is split, delayed, gained, combined and re-amplified, and finally the pulsed laser output with flexible and adjustable pulse shape is realized at the 3 port of the circulator 16, so as to suppress the distortion of the pulse shape in the MOPA structure pulsed fiber laser caused by the gain saturation effect, which causes the pulse leading edge to be too high and the trailing edge to be too low. In this embodiment of the invention, all optical fibers and devices of the laser pulse waveform control system are polarization-maintaining fibers, and the signal laser is linearly polarized light that is transmitted along the fast axis of the polarization-maintaining fiber.

[0034] In one embodiment of the present invention, the broadband pulse seed source 11 has a center wavelength of 1064 nm, an output spectrum 3dB bandwidth of 20 nm, an output pulse signal laser repetition frequency of 135 kHz, a pulse width of 15 ns, and an average power of about 20 mW.

[0035] Furthermore, the first gain fiber 13 and the second gain fiber 20 are double-clad ytterbium-doped fibers with a core diameter of 10 μm, a cladding diameter of 130 μm, and a pump light cladding absorption coefficient of 1.8 dB / m@915 nm. The inner cladding is wrapped in a low-refractive-index outer cladding, which is then wrapped in a coating layer.

[0036] Furthermore, the first pump source 15 and the second pump source 22 are 915nm band semiconductor lasers with output pigtail dimensions of 105 / 125μm; the passive fiber 19 has a length of 3m and a corresponding delay of approximately 15ns.

[0037] Furthermore, the adjustable beam splitter 17 adjusts the splitting power ratio by rotating the lever on the mechanical component. Generally speaking, the power split into the second module is weaker than the power split into the reflective fiber grating 18. The reflective fiber grating 18 has a center wavelength of 1064nm, a reflection spectrum 3dB bandwidth of 8nm, a reflectivity of 99.5%, and the output side pigtail is cut at a 4-degree bevel angle and treated with low-folding adhesive curing.

[0038] The technical solution of the present invention will now be described in conjunction with specific embodiments.

[0039] Example 1: like Figure 1 and Figure 2 As shown, Embodiment 1 provides a laser pulse waveform control system based on incoherent combining and tunable beam splitting, including a broadband pulse seed source 11, a first module, a second module, and a reflective fiber grating 18. The broadband pulse seed source 11, the first module, and the reflective fiber grating 18 are sequentially optically connected along the signal transmission direction. The second module and the first module are optically connected to each other to form a closed loop optical path.

[0040] In Embodiment 1, the first module includes a signal laser beam combiner 12, a first pump unit, a circulator 16, and an adjustable beam splitter 17. The first pump unit includes a first gain fiber 13, a first pump beam combiner 14, and a first pump source 15. The two pigtails at the input end of the signal laser beam combiner 12 are respectively connected to the broadband pulse seed source 11 and the output signal pigtail of the second pump beam combiner 21. The output pigtail is connected to the first gain fiber 13, and the other side of the first gain fiber 13 is connected to the first pump beam combiner 14. The input signal pigtail is connected; the pump pigtail of the first pump combiner 14 is connected to the first pump source 15, the output signal pigtail is connected to port 1 of the circulator 16, port 2 of the circulator 16 is connected to the input pigtail of the adjustable beam splitter 17, and the two output pigtails of the adjustable beam splitter 17 are connected to the input pigtail of the reflective fiber grating 18 and the passive fiber 19, respectively; the pulsed laser signal is amplified and split in the first module to form the first beam beam, which is finally reflected to port 3 of the circulator 16 to enter the subsequent amplification stage.

[0041] In Embodiment 1, the second module includes a passive optical fiber 19 and a second pump unit. The second pump unit includes a second gain optical fiber 20, a second pump combiner 21, and a second pump source 22. The passive optical fiber 19 is connected to the adjustable beam splitter 17 and the second gain optical fiber 20 on both sides, and the second gain optical fiber 20 is connected to the input signal pigtail of the second pump combiner 21 on the other side. The pump pigtail of the second pump combiner 21 is connected to the second pump source 22, and the output signal pigtail is connected to the signal laser combiner 12. The other pulsed signal laser beam (the second split beam) split by the adjustable beam splitter 17 is amplified after passing through an additional optical path difference in the second ring optical path and finally returns to the first module.

[0042] Specifically, the broadband pulse seed source 11 is used to output pulse signal laser. The first module is used to split the signal laser, amplify the gain of the recombined pulse signal laser, and reflect it through the reflective fiber grating 18 to the circulator port 3 for injection into the subsequent amplification stage. The second module is used to perform delay shaping and gain amplification on the split pulse signal laser. In Embodiment 1, through the above structure, the time-domain waveform-tunable pulse signal laser is finally output from the circulator port 3 to enter the subsequent amplification stage for gain amplification.

[0043] In Example 1, the center wavelength of the broadband pulse seed source 11 is 1064nm, the output spectrum 3dB bandwidth is 20nm, the repetition frequency of the output pulse signal laser is 135kHz, the pulse width is 15ns, and the average power is about 20mW. After the seed laser enters the first module, it is amplified by reverse gain and split into two beams by the adjustable beam splitter 17. One beam is reflected by the reflective fiber grating 18 to port 3 of the circulator 16, and the other beam enters the second module where it is amplified by delay and reverse gain. It then enters the first module again through the signal laser combiner 12.

[0044] In Example 1, the broadband pulse seed source 11 has a built-in isolation filter with a center wavelength of 1064nm; the first gain fiber 13 and the second gain fiber 20 are double-clad ytterbium-doped fibers with a core diameter of 10μm and a cladding diameter of 130μm. The pump light cladding absorption coefficient is 1.8dB / m@915nm. The inner cladding is wrapped in a low-refractive-index outer cladding, and then wrapped in a coating layer. In Example 1, the length of the first gain fiber 13 is 3m, and the length of the second gain fiber 20 is 4m; the splitting ratio of the adjustable beam splitter 17 is set to 50:50; the signal laser beam combiner 12 is a 1+1 signal beam combiner with a built-in isolation filter with a center wavelength of 1064nm; the first pump beam combiner 14 and the second pump beam combiner 21 are 1+1 pump signal side pump beam combiners. Specifically, the working process of the laser pulse waveform control system based on incoherent combining and tunable beam splitting provided in Example 1 is as follows: The broadband pulse seed source outputs the initial pulse signal laser (corresponding time-domain waveform as follows) Figure 2 (As shown in Figure 101). The laser enters the first module and is amplified by the first pump unit. It is then split into two beams by the adjustable beam splitter 17. One beam is reflected by the reflective fiber grating 18 to port 3 of the circulator 16. The other beam enters the second module and is delayed by the passive fiber 19 to form the beam shown in Figure 101. Figure 2 The time-domain waveform shown in Figure 102; the two pulses complete incoherent intensity superposition at the signal laser beam combiner 12 to obtain the preliminary synthesized waveform (corresponding to the time-domain waveform as shown in Figure 102). Figure 2 (As shown in Figure 103); after being amplified by the second pump unit in the second module, the beams are combined again to form a further amplified composite waveform (the corresponding time-domain waveform is shown in Figure 103). Figure 2 (As shown in Figure 104); the pulse signal enters the first module and is amplified twice by the first pump unit. Finally, the ideal time-domain pulse waveform after waveform modulation and pre-compensation is output from port 3 of the circulator 16 (the corresponding time-domain waveform is shown in Figure 104). Figure 2 As shown in Figure 105, this effectively corrects the distortion caused by excessively high pulse leading edge and excessively low trailing edge. The pulse signal laser, which is amplified by gain in the second module and then combined into the first module, is amplified again in the first module, which enhances the energy of the trailing edge of the output pulse, thereby pre-compensating for the distortion caused by excessively high pulse leading edge and excessively low trailing edge due to gain saturation effect during subsequent amplification.

[0045] In summary, unlike existing technical solutions, this invention provides a laser pulse waveform control system based on incoherent combining and tunable beam splitting. Its structure includes: a broadband pulse seed source 11, a first module, a second module, and a reflective fiber grating 18. This invention utilizes a circulator 16 and a... The optical path structure, consisting of an adjustable beam splitter 17 with adjustable beam splitting ratio, a reflective fiber grating 18, and a section of passive fiber 19, cleverly controls the time-domain pulse waveform of the signal laser. It pre-shapes the pulse signal laser injected into the main amplification stage, effectively solving the time-domain waveform distortion of the pulse signal caused by gain saturation during the amplification process of the MOPA structure nanosecond pulse fiber laser. Ultimately, it achieves flexible and adjustable pulse waveform output to improve the efficiency and performance of the processing system.

[0046] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A laser pulse waveform control system based on incoherent combining and tunable beam splitting, characterized in that, It includes a broadband pulse seed source, a first module, a second module, and a reflective fiber grating. The broadband pulse seed source, the first module, and the reflective fiber grating are sequentially optically connected along the signal transmission direction. The second module and the first module are optically connected to each other to form a closed loop optical path. The first module amplifies and splits the pulsed laser signal output from the broadband pulse seed source to obtain a first split beam and a second split beam. The reflective fiber grating reflects the first split beam back to the first module and outputs it. The second module delays and amplifies the second split beam and feeds the amplified second split beam back to the first module to achieve incoherent synthesis of the first and second split beams, thereby realizing tunable control of the laser pulse waveform.

2. The laser pulse waveform control system based on incoherent combining and tunable beam splitting according to claim 1, characterized in that, The first module includes a signal laser beam combiner, a first pump unit, a circulator, and an adjustable beam splitter; The signal laser beam combiner has its first input connected to the broadband pulse seed source, its second input connected to the output of the second module, and its output connected to the input of the first pump unit. The output of the first pump unit is connected to the first port of the circulator. The second port of the circulator is connected to the input of the adjustable beam splitter, and its third port is connected to the subsequent amplification stage. The circulator allows the signal laser to propagate from the first port to the second port and from the second port to the third port. The first output of the adjustable beam splitter is connected to the reflective fiber grating, and its second output is connected to the input of the second module.

3. The laser pulse waveform control system based on incoherent combining and tunable beam splitting according to claim 2, characterized in that, The first pump unit includes a first gain fiber, a first pump combiner, and a first pump source; a first end of the first gain fiber is fused to the output end of the signal laser combiner, and a second end is fused to the input end of the first pump combiner; the pump end of the first pump combiner is optically connected to the first pump source, and the output end is optically connected to the first port of the circulator.

4. The laser pulse waveform control system based on incoherent combining and tunable beam splitting according to claim 3, characterized in that, The second module includes a passive optical fiber and a second pump unit. The first end of the passive optical fiber is fused to the second output end of the adjustable beam splitter, and the second end is fused to the input end of the second pump unit. The output end of the second pump unit is optically connected to the second input end of the signal laser beam combiner.

5. The laser pulse waveform control system based on incoherent combining and tunable beam splitting according to claim 4, characterized in that, When the second beam passes through the passive optical fiber, it generates an optical path difference and forms a time-domain delay of one pulse width; the leading edge of the pulse after the time-domain delay completely coincides with the trailing edge of the pulse signal laser output by the broadband pulse seed source, and the optical path difference is greater than the coherence length between the first beam and the second beam.

6. The laser pulse waveform control system based on incoherent combining and tunable beam splitting according to claim 4, characterized in that, The second pump unit includes a second gain fiber, a second pump combiner, and a second pump source; the first end of the second gain fiber is fused to the second end of the passive fiber, and the second end is fused to the input end of the second pump combiner; the pump end of the second pump combiner is optically connected to the second pump source, and the output end is optically connected to the second input end of the signal laser combiner.

7. The laser pulse waveform control system based on incoherent combining and tunable beam splitting according to claim 6, characterized in that, The core diameter of the pigtail fiber of any one of the pump arm of the first pump combiner, the pump arm of the second pump combiner, the first pump source, and the second pump source is 105 μm, and the inner cladding diameter is 125 μm.

8. The laser pulse waveform control system based on incoherent combining and tunable beam splitting according to claim 6, characterized in that, Both the first gain fiber and the second gain fiber are double-clad ytterbium-doped gain fibers; the core diameter of the double-clad ytterbium-doped gain fiber is 10 μm, and the inner cladding diameter is 130 μm; the refractive index of the outer cladding of the double-clad ytterbium-doped gain fiber is lower than that of the inner cladding, and the refractive index of the inner cladding is lower than that of the core; both the first pump source and the second pump source are semiconductor lasers with an output wavelength in the range of 915 nm to 1018 nm.

9. The laser pulse waveform control system based on incoherent combining and tunable beam splitting according to claim 1, characterized in that, The reflective fiber grating is a high-power chirped fiber grating with the same center wavelength as the broadband pulse seed source, a 3dB bandwidth of 8nm, and a reflectivity of not less than 99.5%. The pigtail on the side of the reflective fiber grating away from the tunable beam splitter has a beveled structure, and the end of the pigtail is provided with a curing layer. The refractive index of the curing layer is lower than that of the pigtail.

10. The laser pulse waveform control system based on incoherent combining and tunable beam splitting according to claim 1, characterized in that, The broadband pulse seed source has a spectral width greater than 10 nm; the output signal pigtail of the broadband pulse seed source is a polarization-maintaining fiber with a core diameter of 6 μm and an inner cladding diameter of 125 μm; the pulse signal laser is linearly polarized light and propagates along the fast axis of the polarization-maintaining fiber.

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