A high-power fiber laser, a laser processing device, and a laser processing system
Patent Information
- Application Number
- CN202522538345.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-28
- Publication Date
- 2026-09-15
- Estimated Expiration
- 2035-11-28
AI Technical Summary
[0004]第一方面，本申请提供了一种高功率光纤激光器、激光加工装置和激光加工系统，通过优化泵浦结构、增益光纤分段设计及包层光剥除策略，解决了光纤激光器的放大效率低、非线性效应（如SRS、ASE）显著、光束质量退化等问题，结构简单，成本较低
[0025] In summary, the high-power fiber laser provided in this application includes a seed source module, n amplification stages, and an output module. The seed source module is used to output signal light; the amplification stages are used to amplify the power of the signal light; each amplification stage includes a cladding stripping unit, a gain fiber, a combiner, and a pump source unit; n ≥ 2, where n is a positive integer; wherein, the nth amplification stage includes the nth gain fiber, which includes a first gain fiber segment and a second gain fiber segment; the absorption rate of the pump light by the first gain fiber segment is less than that by the second gain fiber segment; the output module is used to output kW-level high-power laser light. Under high-power laser conditions, the high-power pump light and the high-gain fiber absorption rate cause a large amount of pump light to be converted into signal light, producing significant nonlinear effects. Under the influence of nonlinear effects, more pump light is converted into light other than signal light, reducing the amplification efficiency of the fiber laser and degrading the beam quality. This application employs a scheme where the absorptivity of the first gain fiber is less than that of the second gain fiber. After the high-power pump light enters the nth gain fiber, it first passes through the first gain fiber with a lower absorptivity. After a portion of the pump light is absorbed by the first gain fiber, its power decreases. The lower-power pump light then passes through the second gain fiber with a higher absorptivity, thus balancing the absorptivity of the nth gain fiber for the pump light. This solves problems such as significant nonlinear effects (e.g., SRS, ASE), low amplification efficiency of fiber lasers, and beam quality degradation. The structure is simple and the cost is low.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of fiber laser technology, and more particularly to a high-power fiber laser, a laser processing apparatus, and a laser processing system. Background Technology
[0002] Industrial pulsed fiber lasers mainly include Q-switched fiber lasers and MOPA (Master Oscillator Power Amplifier fiber lasers). Compared to Q-switched lasers, MOPA fiber lasers have advantages such as a wider frequency tuning range and adjustable pulse waveforms, making them more flexible and adaptable to a wider range of applications. MOPA stands for Master Oscillator Power Amplifier, and it consists of a seed source and an amplification stage.
[0003] The primary goal of MOPA fiber lasers is to achieve higher pulse energy and power to expand application possibilities and improve efficiency. Several key challenges exist in achieving high energy and high power. One is fiber nonlinearity, including stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS). Another challenge is amplified spontaneous emission (ASE) in the amplification stage and the overall thermal load of the laser. Addressing the nonlinearity issue involves increasing the nonlinearity threshold. Effective methods include: 1) increasing the laser's spectral linewidth, but this is limited by the bandwidth of the device and the gain fiber, and downstream applications also have strict requirements for spectral width; 2) reducing the length of the gain and power fibers, but the power fiber's optimization effect is limited by downstream application requirements, while shortening the gain fiber requires a higher absorption coefficient, making fiber thermal load a concern; 3) increasing the fiber core diameter, but increasing the core diameter leads to a rapid increase in modes, resulting in beam quality degradation. Summary of the Invention
[0004] In the first aspect, this application provides a high-power fiber laser, a laser processing device, and a laser processing system. By optimizing the pump structure, the segmented design of the gain fiber, and the cladding stripping strategy, it solves the problems of low amplification efficiency, significant nonlinear effects (such as SRS and ASE), and beam quality degradation of fiber lasers. The structure is simple and the cost is low.
[0005] This application proposes a high-power fiber laser, comprising:
[0006] Seed source module, used to output signal light;
[0007] There are n amplification stages for amplifying the power of the signal light; each amplification stage includes a cladding stripping unit, a gain fiber, a combiner, and a pump source unit; n≥2, where n is a positive integer;
[0008] The nth amplification stage includes an nth gain fiber, which includes a first gain fiber segment and a second gain fiber segment; the absorption rate of the pump light by the first gain fiber segment is less than the absorption rate of the pump light by the second gain fiber segment.
[0009] Output module, used to output kW-level high-power laser.
[0010] As a preferred embodiment, the doping concentration of the first gain fiber segment is less than or equal to the doping concentration of the second gain fiber segment.
[0011] As a preferred embodiment, the core diameter of the first gain fiber segment is less than or equal to the core diameter of the second gain fiber segment.
[0012] As a preferred embodiment, the core diameter of the first gain fiber is less than or equal to the core diameter of the second gain fiber.
[0013] As a preferred embodiment, the cladding diameter of the first gain fiber segment is the same as that of the second gain fiber segment.
[0014] As a preferred option, the i-th amplification stage, the (i+1)-th amplification stage, and the (i+2)-th amplification stage are connected by optical fibers;
[0015] The i-th amplification stage includes the i-th gain fiber, the (i+1)-th amplification stage includes the (i+1)-th gain fiber, the (i+2)-th amplification stage includes the (i+2)-th gain fiber, 1≤i<i+1<i+2≤n, where i is an integer;
[0016] Wherein, the core diameter of the i-th gain fiber is less than or equal to the core diameter of the (i+1)-th gain fiber; the core diameter of the (i+1)-th gain fiber is less than or equal to the core diameter of the (i+2)-th gain fiber.
[0017] As a preferred option, n is an even number;
[0018] The first to the n / 2nd amplification stage form a reverse pump optical path, and the n / 2+1th to the nth amplification stage form a forward pump optical path.
[0019] As a preferred option, an isolator is installed after each amplification stage to filter out reverse-transmitted light.
[0020] As a preferred embodiment, the seed source module includes a signal light source and an isolator. The output of the signal light source is connected to the input of the isolator, and the positive output of the isolator is connected to the first stage of amplification.
[0021] As a preferred option, the gain fiber includes a gain fiber.
[0022] As a preferred embodiment, the output module includes a cladding stripping unit for optimizing beam quality and protecting the optical path.
[0023] Secondly, this application provides a laser processing apparatus, including the fiber laser provided in the first aspect.
[0024] In another aspect, this application provides a laser processing system, including the laser processing apparatus provided in the second aspect.
[0025] In summary, the high-power fiber laser provided in this application includes a seed source module, n amplification stages, and an output module. The seed source module is used to output signal light; the amplification stages are used to amplify the power of the signal light; each amplification stage includes a cladding stripping unit, a gain fiber, a combiner, and a pump source unit; n ≥ 2, where n is a positive integer; wherein, the nth amplification stage includes the nth gain fiber, which includes a first gain fiber segment and a second gain fiber segment; the absorption rate of the pump light by the first gain fiber segment is less than that by the second gain fiber segment; the output module is used to output kW-level high-power laser light. Under high-power laser conditions, the high-power pump light and the high-gain fiber absorption rate cause a large amount of pump light to be converted into signal light, producing significant nonlinear effects. Under the influence of nonlinear effects, more pump light is converted into light other than signal light, reducing the amplification efficiency of the fiber laser and degrading the beam quality. This application employs a scheme where the absorptivity of the first gain fiber is less than that of the second gain fiber. After the high-power pump light enters the nth gain fiber, it first passes through the first gain fiber with a lower absorptivity. After a portion of the pump light is absorbed by the first gain fiber, its power decreases. The lower-power pump light then passes through the second gain fiber with a higher absorptivity, thus balancing the absorptivity of the nth gain fiber for the pump light. This solves problems such as significant nonlinear effects (e.g., SRS, ASE), low amplification efficiency of fiber lasers, and beam quality degradation. The structure is simple and the cost is low. Attached Figure Description
[0026] Figure 1 A schematic diagram of the optical path of a high-power fiber laser provided by the present invention;
[0027] Figure 2The present invention provides a schematic diagram of the optical path of a high-power fiber laser; in the figure: 101, first gain fiber; 102, second gain fiber; 01, seed source module; 02, amplification stage; 03, output module; 1, seed source; 2, first isolator; 3, first cladding stripping unit; 4, first gain fiber; 5, first combiner; 6, first pump source unit; 7, second isolator; 8, second cladding stripping unit; 9, second gain fiber; 10, second combiner; 11. 12. Second pump source unit; 13. Third isolator; 14. Third cladding optical stripping unit; 15. Third combiner; 16. Third gain fiber; 17. Fourth cladding optical stripping unit; 18. Fourth isolator; 19. Fifth cladding optical stripping unit; 21. Fourth combiner; 20. Fourth pump source unit; 22. Fourth gain fiber; 23. Sixth cladding optical stripping unit; 24. Fifth isolator; 25. Seventh cladding optical stripping unit; 26. High-power output head. Detailed Implementation
[0028] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the present application and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present application are shown in the drawings, not the entire structure. Various modifications and variations can be made to the present application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, the present application is intended to cover modifications and variations falling within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the implementation methods provided in the embodiments of the present application can be combined with each other without contradiction.
[0029] Figure 1 This is a schematic diagram of the optical path of a high-power fiber laser provided by the present invention. Figure 2 This is a schematic diagram of the optical path of a high-power fiber laser provided by the present invention, for reference. Figures 1-2 The high-power fiber laser provided in this application embodiment includes a seed source module 01, n amplification stages 02, and an output module 03.
[0030] Seed source module 01 is used to output signal light. Exemplarily, seed source module 01 includes, for example, a semiconductor laser, capable of outputting signal light in the near-infrared band (e.g., 650 nm, 780 nm, 850 nm) with editable waveform profiles. This seed source supports flexible adjustment of pulse parameters (e.g., pulse width, repetition frequency) and has the advantages of small size and high electro-optical conversion efficiency.
[0031] The signal light output terminal of the seed source module 01 is connected to n amplification stages 02, which are used to amplify the power of the signal light. Where n ≥ 2, and n is a positive integer. For example, this application includes... Figure 1 The following explanation uses four amplification stages as an example; other embodiments will not be shown here.
[0032] Each amplification stage 02 includes a cladding stripping unit, a gain fiber, a combiner, and a pump source unit. The cladding stripping unit filters out residual pump light and parasitic modes, while the gain fiber amplifies optical power; in this embodiment, a gain fiber is used. The combiner couples the signal light and the pump light. The pump source unit provides pump energy.
[0033] The nth amplification stage 02n employs a segmented gain fiber structure, optimizing heat distribution and suppressing nonlinear effects by controlling mode field differences. Specifically, the nth amplification stage 02n includes an nth gain fiber, which comprises a first gain fiber segment 101 and a second gain fiber segment 102. This invention uses a combination of two mode field difference fibers to control the temperature distribution and nonlinear effects of the nth gain fiber. The absorption rate of the pump light by the first gain fiber segment 101 is set to be less than that by the second gain fiber segment 102, resulting in a simple structure and low cost.
[0034] In this application Figure 2 In the illustrated embodiment, the nth amplification stage 02n employs a unidirectional pump optical path, with the first gain fiber 101 positioned close to the pump source and the second gain fiber 102 positioned away from the pump source. It should be understood that, in one embodiment of this application, if the nth amplification stage 02n employs a bidirectional pump optical path, then the two first gain fiber segments 101 are positioned close to the two pump sources, and the second gain fiber 102 is sandwiched between the two first gain fiber segments 101, or a first gain fiber 101 is connected to a second gain fiber 102; all of these configurations should be within the scope of this application.
[0035] For example, in this application, the doping concentration of the first gain fiber 101 is lower than the doping concentration of the second gain fiber 102, so that the absorption rate of the pump light by the first gain fiber 101 is lower than the absorption rate of the pump light by the second gain fiber 102. It should be understood that measures such as setting the core diameter of the first gain fiber 101 to be smaller than the diameter of the second gain fiber 102, or other measures that change the absorption rate of the gain fiber to make the first gain fiber 101 absorb less pump light than the second gain fiber 102, should also be within the scope of protection of this application.
[0036] Preferably, the doping concentration of the first gain fiber 101 is less than or equal to the doping concentration of the second gain fiber 102. Having a core diameter smaller than that of the second gain fiber 102 can further reduce the absorption rate of the first gain fiber 101 to the pump light, thereby controlling the temperature distribution and nonlinear effects. It should be understood that the core diameter of the first gain fiber 101 can be equal to that of the second gain fiber 102, and this is still within the scope of this application.
[0037] Preferably, the core diameter of the first gain fiber 101 is less than or equal to the core diameter of the second gain fiber 102. Having a smaller core diameter for the first gain fiber 101 than the second gain fiber 102 can further reduce the absorption rate of the first gain fiber 101 to the pump light, thereby controlling the temperature distribution and nonlinear effects; or, having a core diameter equal to the second gain fiber 102 can reduce the processing difficulty.
[0038] Preferably, the cladding diameter of the first gain fiber 101 and the cladding diameter of the second gain fiber 102 are the same. When splicing the two fiber segments, a fusion splicer with cladding alignment can be used instead of a fusion splicer with fiber core alignment, which reduces costs and processing difficulty.
[0039] In one embodiment of this application, for example, the core diameter near the input end of the first gain fiber 101 is 100–300 μm (smaller mode field), with a low pump absorption rate, which serves to reduce heat accumulation. The core diameter near the output end of the second gain fiber 102 is 200–600 μm (larger mode field), with a higher pump absorption rate, which can improve energy extraction efficiency. The common parameter of the first gain fiber 101 and the second gain fiber 102 is that the cladding diameter of both segments is 300–1000 μm, which ensures splice compatibility.
[0040] The nth amplification stage 02n is connected to the output module 03, ultimately outputting a kW-level high-power laser. This exemplary embodiment of the invention employs a four-stage amplification structure (n=4), but the amplification structure can also take other numbers of stages, such as a three-stage amplification (n=3) or n taking any other positive integer greater than or equal to 2. This embodiment of the invention does not impose any limitations.
[0041] For example, in this embodiment of the invention, the gain fiber is ytterbium-doped fiber, but the gain fiber can also be replaced with other rare earth-doped fibers, such as erbium-ytterbium co-doped fiber, etc., and this embodiment of the invention does not impose any restrictions.
[0042] Specifically, this embodiment of the invention employs a four-stage amplification architecture (021→022→023→024) to achieve high-power output, with ytterbium-doped fiber used for the gain fiber. A typical configuration of a high-power fiber laser is as follows:
[0043] refer to Figure 2 The seed source module 01 includes a seed source 1 and a first isolator 2. For example, the seed source 1 uses a semiconductor laser with a signal light wavelength of 1064nm (tunable) and a signal light power of 10-100mW, and the first isolator 2 has an isolation degree of >30dB.
[0044] The first amplification stage 021 includes a first cladding light stripping unit 3, a first gain fiber 4, a first combiner 5, a first pump source unit 6, and a second isolator 7, all connected by optical fibers. The input of the first cladding light stripping unit 3 is connected to the output of the first isolator 2, and the first pump source unit 6 is connected to the pump fiber of the first combiner 5 to provide the first pump light.
[0045] The second-stage amplification stage 022 includes a second cladding stripping unit 8, a second gain fiber 9, a second combiner 10, a second pump source unit 11, and a third isolator 12, all connected by optical fibers. The input of the second cladding stripping unit 8 is connected to the output of the second isolator 7, and the second pump source unit 12 is connected to the pump fiber of the second combiner 10 to provide the second pump light.
[0046] The third amplification stage 023 includes a third cladding light stripping unit 13, a third pump source unit 14, a third combiner 15, a third gain fiber 16, a fourth cladding light stripping unit 17, and a fourth isolator 18, all connected by optical fibers. The input of the third cladding light stripping unit 13 is connected to the output of the third isolator 12, and the third pump source unit 12 is connected to the pump fiber of the third combiner 15 to provide the third pump light.
[0047] The fourth amplification stage 024 includes a fifth cladding light stripping unit 19, a fourth combiner 21, a fourth pump source unit 20, a fourth gain fiber 22, a sixth cladding light stripping unit 23, and a fifth isolator 24, all connected by optical fibers. The input of the fifth cladding light stripping unit 19 is connected to the output of the fourth isolator 18, and the fourth pump source unit 20 is connected to the pump fiber of the fourth combiner 21 to provide pump light.
[0048] The output module 03 includes a seventh cladding light stripping unit 25 and a high-power output head 26.
[0049] The seed source module 01, first-stage amplifier stage 021, second-stage amplifier stage 022, third-stage amplifier stage 023, fourth-stage amplifier stage 024, and output module 03 are connected by optical fibers. The first-stage amplifier stage 021 and second-stage amplifier stage 022 use reverse-pumped optical paths, which helps reduce ASE (Acoustic Emissions). The third-stage amplifier stage 023 and fourth-stage amplifier stage 024 use forward-pumped optical paths, which helps improve power extraction efficiency.
[0050] The first two gain fibers (4 and 9) of the first two amplification stages use 10 / 125μm gain fibers, while the third gain fiber (16) and fourth gain fiber (22) of the latter two amplification stages use 20 / 400μm large-mode-field fibers. Here, 10 / 125μm refers to a fiber core diameter of 10μm and a cladding diameter of 125μm. The first pump source unit 6, the second pump source unit 11, the third pump source unit 14, and the fourth pump source unit 20 use wavelength-locked 976nm pump lasers, with power gradient configurations of 50W, 200W, 500W, and 1000W.
[0051] refer to Figure 2 The working principle of a high-power fiber laser with four amplification stages is as follows:
[0052] Signal light emission: Seed source 1 of seed source module 01 outputs a uW level signal light with waveform editing. The first isolator 2 uses bandpass filtering to optimize the signal spectral characteristics and protect the seed source.
[0053] First-stage power amplification: The first amplification stage 021 employs a reverse pump optical path. The first combiner 5 couples the first pump light emitted by the first pump source unit 6 into the main optical path, where it is absorbed by the first gain fiber 4. The signal light, after passing through the first gain fiber 4, has its energy extracted from high-energy particles and amplified. It is then transmitted through the first combiner 5 and isolated by the second isolator 7 before being output. The first-stage amplification stage can amplify the signal light from the μW level to the mW level, forming the first-stage signal light. For other components of light, the first cladding light stripping unit 3 eliminates residual first pump light (efficiency > 98%), the second isolator 7 filters out forward ASE light (suppression ratio > 35dB), and the reverse-transmitted ASE light is jointly suppressed and filtered out by the first cladding light stripping unit 3 and the second isolator 7.
[0054] Second-stage power amplification: The second amplification stage 022 is a reverse pump optical path. The second beam combiner 10 couples the second pump light emitted by the second pump source unit 11 into the main optical path, where it is absorbed by the second gain fiber 9. The first-stage signal light transmitted from the second amplification stage 021 passes through the second cladding stripping unit 8 to remove the cladding light, optimizing the beam quality. This first-stage signal light then passes through the second gain fiber 9, where the energy of high-energy particles is extracted and amplified. After transmission through the second beam combiner 10 and isolation by the third isolator 12, it is output. The second amplification stage 022 amplifies the first-stage signal light with mW-level optical power to the W-level, forming the second-stage signal light. For other components of light, the second cladding stripping unit 8 absorbs the residual second pump light (efficiency > 98%), the third isolator 12 filters out the forward ASE light (suppression ratio > 35dB), and the reverse-transmitted ASE light is jointly suppressed and filtered out by the second cladding stripping unit 8 and the third isolator 12.
[0055] Third-stage power amplification: The third amplification stage 023 is the forward pump optical path. The third combiner 15 couples the third pump light emitted by the third pump unit 14 into the main optical path, where it is absorbed by the third gain fiber 16. The second signal light transmitted from the second amplification stage 022 passes through the third cladding light stripping unit 13 to remove the cladding light, optimizing the beam quality. It then passes through the third combiner 15 into the third gain fiber 16 to extract the energy of high-energy particles for amplification. After passing through the fourth cladding light stripping unit 17 to remove the cladding light, it is output from the fourth isolator 18. The third amplification stage 023 amplifies the W-level second-stage signal light to the hundreds of W level, forming the third-stage signal light. For other components of light, the third cladding light stripping unit 13 and the fourth cladding light stripping unit 17 absorb the residual third pump light, and the fourth isolator 18 filters out the forward ASE light (suppression ratio > 35dB). The reverse-transmitted ASE light is jointly suppressed and filtered out by the third cladding light stripping unit 13, the fourth cladding light stripping unit 17, and the fourth isolator 18.
[0056] Fourth-stage power amplification: The fourth amplification stage 024 is the forward pump optical path. The fourth combiner 21 couples the fourth pump light emitted by the fourth pump unit 20 into the main optical path, where it is absorbed by the fourth gain fiber 22. The fourth gain fiber 22 is a large-mode-field gain fiber with a different pump light absorption rate. The first gain fiber 101 has a low absorption rate; one end is fused to the fourth combiner 21, and the other end is fused to the second gain fiber 102 with a high absorption rate. This facilitates reasonable control of temperature distribution, SRS, and ASE. Preferably, the two cladding segments have the same diameter, allowing the use of a cladding-aligned fusion splicer instead of a core-aligned fusion splicer, thus reducing costs. Specifically, the third-stage signal light transmitted from the third-stage amplification stage 023 undergoes cladding removal by the fifth cladding stripping unit 19 to optimize beam quality. It then passes through the fourth combiner 21 into the fourth gain fiber 22 to extract and amplify the energy of high-energy particles. After further cladding removal by the sixth cladding stripping unit 23, it is output from the fifth isolator 24. The fourth amplification stage 024 amplifies the W-level third-stage signal light to the kW-level, forming the fourth-stage signal light. For other components of the light, the fifth and sixth cladding stripping units 19 and 23 absorb residual fourth-stage pump light, and the fifth isolator 24 filters out forward ASE light (suppression ratio > 25dB). The reverse-transmitted ASE light is jointly suppressed and filtered out by the fifth cladding stripping unit 19, the sixth cladding stripping unit 23, and the fifth isolator 24.
[0057] It should be noted that this invention uses a first-segment gain fiber 101 with low pump light absorption rate spliced with a second-segment gain fiber 102 with high pump light absorption rate as a single-stage gain fiber in the nth amplification stage. This can improve the extraction efficiency of high-energy particles, suppress ASE and nonlinear effects, and enhance optical-to-optical conversion efficiency. The basic principle is as follows:
[0058] ① Low pump light absorptivity gain fibers have fewer doped particles and lower ASE (absorption rate of light).
[0059] ② High pump light absorptivity gain fibers have more doped particles and lower SRS.
[0060] ③ By splicing a low-pump-absorption-rate gain fiber with a high-pump-absorption-rate gain fiber, the pre-stage signal light first enters the low-pump-absorption-rate fiber for amplification, and then enters the high-pump-absorption-rate fiber for amplification. This method makes full use of the characteristics of the two fibers, thereby reducing both ASE and SRS.
[0061] Furthermore, the present invention employs a dual-stage isolation design between adjacent amplification stages, such as a first isolator 2 and a second isolator 7. This ensures that the seed source is protected from reverse power surges and improves optical stability between amplification stages. A temperature monitoring point can also be placed at the junction of the pump source unit and the gain fiber to prevent light leakage and heat generation.
[0062] After the fourth-stage signal light is transmitted into the output module 04, it outputs a laser with a power level of kW. The seventh cladding stripping unit 25 can strip the front-end cladding light, optimizing beam quality, and also strips the returning cladding light, protecting the optical path components. After four stages of amplification, the laser power output from the high-power output head 26 can reach the kW level, with a peak power reaching the MW level.
[0063] The high-power fiber laser provided in this invention, by rationally adjusting the amplification factor of each stage and controlling the temperature of each optical path, can achieve high-power, high-energy pulse output with good beam quality. This method can suppress ASE and SRS, and the basic principle is as follows:
[0064] First, ASE is related to the energy of unused particles in the upper energy level within the cavity; the more residual energy, the greater the ASE. Therefore, it is necessary to extract the energy of particles in the upper energy level as quickly as possible to reduce ASE and increase signal power, which can effectively reduce ASE. Based on this, the present invention sets a cladding light stripping unit in each energy level to absorb residual pump light and an isolator to suppress ASE light propagating in the opposite direction.
[0065] Secondly, SRS is related to core diameter, length, and power. With a fixed core diameter and length, the lower the signal power inside the optical fiber, the lower the SRS.
[0066] Finally, this application uses a first gain fiber 101 with low pump light absorption rate spliced with a second gain fiber 102 with high pump light absorption rate as a single gain fiber for the nth amplification stage, which can effectively suppress ASE and SRS effects.
[0067] In some embodiments, reference Figure 2When using n-stage amplification, the first stage amplification stage 02 includes the first gain fiber, and the (n-1)th stage amplification stage 02 includes the (n-1)th gain fiber. In the embodiments of the invention, the first to (n-1)th gain fibers can be the same, which can reduce the types of optical fibers, simplify the splicing process, and ensure the optical signal transmission performance between amplification stages.
[0068] In some embodiments, reference Figure 2 The i-th amplification stage 02, the (i+1)-th amplification stage 02, and the (i+2)-th amplification stage 02 are connected by optical fibers. The i-th amplification stage 02 includes the i-th gain fiber, the (i+1)-th amplification stage 02 includes the (i+1)-th gain fiber, and the (i+2)-th amplification stage 02 includes the (i+2)-th gain fiber, where 1 ≤ i < i+1 < i+2 ≤ n, and i is an integer. The core diameter of the i-th gain fiber is less than or equal to the core diameter of the (i+1)-th gain fiber, and the core diameter of the (i+1)-th gain fiber is less than or equal to the core diameter of the (i+2)-th gain fiber. In this embodiment of the invention, the arrangement of the cores of the power transmission and gain fibers at each stage from small to large can be combined, and the winding method of each fiber can be adjusted to control the propagation mode and beam quality in the optical fiber. For example, each fiber stage can use a differentiated winding radius (R1 < R2 < R...). n This method utilizes bending loss to selectively filter out higher-order modes, gradually adapting to power growth and avoiding the accumulation of nonlinear effects. The basic principle is as follows:
[0069] 1) The modes present in an optical fiber are related to its core diameter and NA. Larger core diameters and NAs result in more modes, leading to poorer beam quality. Smaller core diameter fibers have fewer modes, making mode control easier. Therefore, in this embodiment of the invention, a first gain fiber 101 with low pump light absorption rate is fused with a gain fiber 102 with high pump light absorption rate in the nth amplification stage to form a single-stage gain fiber, thus controlling the modes.
[0070] 2) When inserting a large-core-diameter fiber into a small-core-diameter fiber, light leakage may occur due to structural differences and mode issues, leading to power loss. Therefore, in this embodiment of the invention, the nth amplification stage uses a large-mode-field gain fiber with a uniform cladding diameter but different core sizes.
[0071] 3) Different propagation modes have different sensitivities to fiber bending, and this characteristic also changes with the specifications of the fiber. This invention can help control the propagation mode by reasonably adjusting the winding method of each level of fiber.
[0072] In some embodiments, reference Figure 2Along the optical amplification direction of the main optical axis, the first amplification stage 02 includes the first gain fiber, the (n-1)th amplification stage 02 includes the (n-1)th gain fiber, and the nth amplification stage 02 includes the nth gain fiber. The core diameter of the first gain fiber gradually increases from the (n-1)th gain fiber to the nth gain fiber, which is beneficial for controlling the laser mode.
[0073] Based on the above embodiments, n is an even number. The first amplification stage 02 to the n / 2th amplification stage 02 are reverse pump optical paths, and the n / 2+1th amplification stage 02 to the nth amplification stage 02 are forward pump optical paths.
[0074] Based on the above embodiments, an isolator is provided after each amplification stage 02 to filter out reverse-transmitted light. Therefore, this invention incorporates an isolator in each energy level. The isolator isolates the reverse-transmitted light while also serving a filtering function, ensuring the safety of the preceding optical path and effectively suppressing reverse-transmitted ASE light.
[0075] Based on the above embodiments, in the entire optical path system, the gain fiber includes ytterbium-doped fiber. The ytterbium-doped fiber serves as the working medium, providing the energy conversion and transforming the lower-brightness pump light into higher-brightness signal light.
[0076] Among them, the isolator is a key component to ensure the stability of the laser system. It can isolate the reverse-transmitted light and also has a filtering function, thus ensuring the safety of the front-end optical path.
[0077] The cladding light filtering unit filters out light present in the cladding, protecting optical components and ensuring optimized beam quality. It can also be understood as a mode stripper, a device that removes cladding laser light from a fiber laser without losing core laser light. It is widely used in medium / high / low fiber lasers, playing a crucial role in improving laser beam quality and reducing backscattered laser light.
[0078] Among them, the combiner is a conventional pump combiner, which can couple the signal light and the pump light into the same optical fiber, thus playing the role of energy coupling;
[0079] Among them, the high-power output head can reduce the energy density of the output laser at the output end face, thus providing an output window for the whole machine.
[0080] In summary, the embodiments of this invention employ a first-segment gain fiber with low pump light absorptivity followed by a second-segment gain fiber 102 with high pump light absorptivity as a single-stage gain fiber in the nth amplification stage. Under high-power laser conditions, the high power pump light and the high-gain fiber absorptivity result in a large amount of pump light being converted into signal light, producing significant nonlinear effects. Under the influence of these nonlinear effects, more pump light is converted into light other than signal light, reducing the amplification efficiency of the fiber laser and degrading beam quality. This application adopts a scheme where the absorptivity of the first-segment gain fiber is lower than that of the second-segment gain fiber. After the high-power pump light enters the nth gain fiber, it first passes through the first-segment gain fiber with lower absorptivity. After a portion of the pump light is absorbed by the first-segment gain fiber, its power decreases. The lower-power pump light then passes through the second-segment gain fiber with higher absorptivity, balancing the absorptivity of the nth-segment gain fiber for the pump light. This solves the problems of significant nonlinear effects (such as SRS and ASE), low amplification efficiency of the fiber laser, and beam quality degradation. The structure is simple and the cost is low.
[0081] Based on the same inventive concept, this application also provides a laser processing apparatus, which includes the high-power fiber laser provided in the above embodiments. The fiber laser is used to provide a processing light source. Therefore, the laser processing apparatus also has the beneficial effects of the high-power fiber laser in the above embodiments. The similarities can be understood with reference to the explanation of the high-power fiber laser above, and will not be repeated below.
[0082] It should be noted that the laser processing device also includes a precision processing platform, controller, etc., which work together to realize multi-dimensional processing operations of the product, which will not be elaborated here.
[0083] Based on the same inventive concept, this application also provides a laser processing system, which includes the laser processing apparatus provided in the above embodiments.
[0084] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Features of various embodiments of the present invention can be partially or wholly coupled or combined with each other, and can cooperate and be technically driven in various ways. Various obvious changes, readjustments, combinations, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims
1. A high-power fiber laser, characterized in that, include: Seed source module, used to output signal light; n amplification stages are used to amplify the power of the signal light; each amplification stage includes a cladding stripping unit, a gain fiber, a combiner, and a pump source unit. n≥2, where n is a positive integer; The nth amplification stage includes an nth gain fiber, which comprises a first gain fiber segment and a second gain fiber segment. The absorption rate of the pump light by the first gain fiber segment is less than that by the second gain fiber segment.
2. The fiber laser according to claim 1, characterized in that, The doping concentration of the first gain fiber segment is less than or equal to the doping concentration of the second gain fiber segment.
3. The fiber laser according to claim 1, characterized in that, The core diameter of the first gain fiber segment is less than or equal to the core diameter of the second gain fiber segment.
4. The fiber laser according to claim 1, characterized in that, The cladding diameter of the first gain fiber segment is the same as that of the second gain fiber segment.
5. The fiber laser according to claim 1, characterized in that, The i-th amplification stage, the (i+1)-th amplification stage, and the (i+2)-th amplification stage are connected by optical fibers; The i-th amplification stage includes the i-th gain fiber, the (i+1)-th amplification stage includes the (i+1)-th gain fiber, the (i+2)-th amplification stage includes the (i+2)-th gain fiber, 1≤i<i+1<i+2≤n, where i is an integer; Wherein, the core diameter of the i-th gain fiber is less than or equal to the core diameter of the (i+1)-th gain fiber; the core diameter of the (i+1)-th gain fiber is less than or equal to the core diameter of the (i+2)-th gain fiber.
6. The fiber laser according to claim 1, characterized in that, n is an even number; The first to the n / 2nd amplification stage form the reverse pump optical path, and the n / 2+1th to the nth amplification stage form the forward pump optical path.
7. The fiber laser according to claim 1, characterized in that, An isolator is installed after each amplification stage to filter out reverse-transmitted light.
8. The fiber laser according to claim 1, characterized in that, The seed source module includes a signal light source and an isolator. The output terminal of the signal light source is connected to the input terminal of the isolator, and the positive output terminal of the isolator is connected to the first stage amplification stage.
9. A laser processing apparatus, characterized in that, Includes the fiber laser as described in any one of claims 1-8.
10. A laser processing system, characterized in that, Includes the laser processing apparatus as described in claim 9.