Back-reflection-resistant high-power fiber laser apparatus, and method

Abstract

Provided in the present invention is a back-reflection-resistant high-power fiber laser apparatus. A workpiece state check module detects the state of a processing region of a workpiece; a regulation module sets processing parameters on the basis of the state detected by the workpiece state check module; a laser module generates an auxiliary laser and a main laser on the basis of the processing parameters, and adjusts the output power of the auxiliary laser and the output power of the main laser, wherein the auxiliary laser is used for performing preheating and / or surface melting on the processing region, and the main laser is used for performing deep processing on the processing region; when the workpiece state check module detects that the processing region has not yet been melted, the regulation module reduces the output power of the main laser; and when the workpiece state check module detects that the processing region has undergone melting, the regulation module increases the output power of the main laser. By means of deep integration of the overall structure and functions, both efficient laser output and a reduction in the loss of a laser device caused by back-reflected light are achieved.

Description

A device and method for anti-back-feedback high-power fiber laser Technical Field

[0001] This invention relates to the field of high-power lasers, and more specifically, to an anti-backflow high-power fiber laser device and method. Background Technology

[0002] Infrared lasers (wavelengths between 1050-1080 nm) are widely used in laser metal processing due to their high metal absorption rate. This wavelength of laser can penetrate metal deeply, making it suitable for deep and high-efficiency processing. However, at room temperature, most metals exist in a solid state, and their reflectivity to infrared lasers is higher than that to blue light (420-470 nm) or green light (532 nm). For example, as shown in Figure 6b, many metals have significantly higher reflectivity to 1064 nm infrared lasers than to blue or green light, while as shown in Figure 6a, many metals have significantly higher absorption rates to blue light than to infrared lasers.

[0003] When the surface of highly reflective materials (gold, silver, copper, aluminum, etc.) is heated to a molten, liquid state, their absorption rate of infrared lasers increases significantly, as shown in Figure 7 (taking metallic copper (Cu) as an example). Figure 7 shows the absorption rate curves of copper for infrared lasers (wavelengths of 1030–1080 nm) at different temperatures. At room temperature, copper has a low absorption rate for infrared lasers, but as the temperature rises and approaches its melting point (1084.62℃, approximately 1357.77 K), the absorption rate increases significantly, making it easier for copper to absorb infrared laser energy.

[0004] Therefore, to process high-reflectivity metallic materials more efficiently, the workpiece surface is typically preheated with blue light (420-470 nm) before using infrared laser. Due to its shorter wavelength, blue light has higher photon energy and a higher absorption rate in room-temperature solid metallic materials, thus rapidly heating the material surface to melting point and forming a molten pool. The formation of the molten pool reduces surface reflectivity and increases the absorption efficiency of the infrared laser, which is then used for deep processing. This process combines the high efficiency of blue light preheating with the deep processing capabilities of infrared laser, thereby achieving high-quality processing of high-reflectivity metallic materials.

[0005] However, in existing technologies, the power of infrared and blue lasers is usually fixed and cannot be dynamically adjusted according to the real-time conditions of the processing area (such as the reflectivity of the reflected light and the temperature changes of the workpiece). This deficiency is particularly evident during the processing, especially during the transition of the workpiece from a solid to a liquid state, where the need for reasonable allocation of the two laser powers and dynamic adjustment of the output time is especially important.

[0006] Due to the lack of a dynamic adjustment mechanism, existing technologies suffer from low laser utilization. The power of infrared and blue lasers cannot be flexibly allocated according to processing requirements, leading to unnecessary energy waste. During processing, reflected light from high-reflectivity areas may be reflected back to the laser, entering the laser source system and damaging the laser, reducing its lifespan and reliability. The lack of optimized power allocation between the two lasers before and after melting makes it impossible to achieve a balance between efficiency and quality in the processing. Therefore, this invention proposes a technical solution that can adjust the appropriate laser power in real time based on the reflected light reflectivity and temperature feedback of the processing area, thereby improving laser utilization and reducing equipment wear.

[0007] Comparative analysis of existing technologies:

[0008] Patent application number 202110860411.8 primarily uses blue laser light to preheat the area around the pump laser processing focus, aiming to reduce the temperature difference between the focus area and the surrounding area to avoid sputtering during processing. However, this technology fails to dynamically adjust the power of the auxiliary laser and the pump laser based on the real-time state of the processing area (such as reflected light reflectivity and temperature).

[0009] Patent application number 202310187916.1: Fiber-Blue Semiconductor Composite Laser

[0010] The laser spot energy is shifted to achieve intelligent energy distribution of the composite laser on dissimilar materials, and the energy distribution ratio is intelligently adjusted by real-time monitoring of weld morphology and temperature feedback. By improving the intelligent distribution of laser energy on both sides of the base material, the thickness of the intermetallic compound reaction layer is effectively reduced, the joint strength is improved, and high-quality welding of dissimilar materials is achieved. Although this technology achieves the adjustment of composite laser energy distribution for different materials, it fails to adjust the energy distribution between the fiber laser and the blue semiconductor laser in the composite laser, and does not propose a processing method for a single workpiece material.

[0011] Patent application number 202410478258.6: does not involve the technical content of real-time adjustment of laser energy distribution based on the reflectivity and temperature feedback of the processing area.

[0012] Furthermore, current technologies typically only support assembly line processing of workpieces made of the same material. If a change in processing material or processing requirements is needed, the laser parameters must be manually adjusted. Current technologies cannot automatically identify workpiece materials and automatically set the optimal power configuration for infrared and blue lasers based on material characteristics, thus affecting processing efficiency and flexibility.

[0013] This invention proposes a technical solution for real-time adjustment of the power distribution between infrared and blue lasers based on the reflected light reflectivity and temperature feedback of the processing area. This solution not only solves the problems of laser energy waste and equipment wear, but also automatically identifies the workpiece material and dynamically optimizes the laser parameter configuration, significantly improving processing efficiency and quality. Summary of the Invention

[0014] This invention provides a device and method for anti-return high-power fiber lasers, which can balance efficient laser utilization and reduce the loss of laser core components caused by return light.

[0015] In a first aspect, the present invention provides an anti-return high-power fiber laser device, including a control module, a laser module, and a workpiece status inspection module;

[0016] The workpiece status inspection module detects the status of the workpiece's processing area;

[0017] The control module sets processing parameters based on the status detected by the workpiece status inspection module.

[0018] The laser module generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser. The auxiliary laser is used to preheat and / or melt the surface of the processing area, and the main laser is used to perform deep processing on the processing area.

[0019] When the workpiece status inspection module detects that the processing area has not melted, the control module reduces the output power of the main laser;

[0020] When the workpiece status inspection module detects that the processing area has melted, the control module increases the output power of the main laser.

[0021] In a second aspect, the present invention provides a method for preventing backtracking in a high-power fiber laser, comprising:

[0022] Inspect the condition of the workpiece's machining area;

[0023] Set processing parameters based on the state of the processing area;

[0024] The laser generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser. The auxiliary laser is used to preheat and / or melt the surface of the processing area, and the main laser is used to perform deep processing on the processing area.

[0025] If no melting occurs in the processing area, reduce the output power of the main laser;

[0026] If melting occurs in the processing area, increase the output power of the main laser.

[0027] The beneficial technical effects of this invention are as follows:

[0028] 1. Spatial coupling semiconductor chips reduce the size of the pump source;

[0029] 2. The reflectivity of the backlight in the workpiece processing area improves the accuracy of automatically identifying the workpiece material type and judging the state of the processing area.

[0030] 3. Real-time control of laser output based on the status of the processing area improves the efficient use of laser, ensures the stability of the processing process and results, and reduces damage to the laser from reflected light.

[0031] 4. The addition of the cladding stripper effectively strips away excess pump light and return light, further improving the stability and processing efficiency of the laser. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 is a schematic diagram of a high-power fiber laser device with anti-backflow provided by the present invention;

[0034] Figure 2 is a schematic diagram of the control module provided by the present invention;

[0035] Figure 3 is a schematic diagram of the laser module provided by the present invention;

[0036] Figure 4 is a schematic diagram of the cladding optical stripper provided by the present invention;

[0037] Figure 5 is a flowchart of a method for anti-back-return high-power fiber laser provided by the present invention;

[0038] Figures 6a and 6b show the absorption and reflectance curves of different metallic materials for different wavelengths of light at room temperature, respectively.

[0039] Figure 7 shows the absorption rate curves of copper for infrared laser (wavelength 1050-1080 nm) at different temperatures;

[0040] Figure 8 shows the absorption and emission curves of ytterbium-doped gain fiber for light of different wavelengths. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0042] Invention Overview

[0043] This invention provides a highly efficient laser processing system. The control module and workpiece status inspection module work together to automatically identify the workpiece material type based on the reflectivity of the main laser's reflected light and temperature feedback, and dynamically adjust the output power of the laser module. This not only improves the efficiency and quality of laser processing but also reduces resource waste and extends the module's lifespan. Through deep integration of the overall structure and functions, it balances high-efficiency laser output with reduced laser loss due to reflected light.

[0044] Exemplary device

[0045] As shown in Figure 1, the present invention provides a high-power laser, which includes a control module 1, a laser module 2, and a workpiece status inspection module 3.

[0046] The workpiece status inspection module 3 also includes a temperature detection module 3-1 and a backlight detection module 3-2. The temperature detection module 3-1 is used to detect the temperature of the workpiece processing area, and the backlight detection module 3-2 is used to detect the reflectivity of the main laser in the backlight of the processing area. Both modules perform real-time detection throughout the process and continuously feed the detected data back to the control module 1.

[0047] As shown in Figure 2, the control module 1 further includes:

[0048] Materials Database 1-1 is used to store reflectance data of common materials at different temperatures, especially reflectance data near the melting point;

[0049] The material identification unit 1-2 is used to compare the workpiece surface temperature measured by the temperature detection module 3-1 and the reflectivity data measured by the retroreflection detection module 3-2 with the material properties in the material database, and match the closest material type according to the characteristic curve of reflectivity changing with temperature.

[0050] Parameter adjustment units 1-3 are used to determine the initial processing parameters based on the workpiece material type and processing requirements (e.g., cutting or welding), and to adjust the processing parameters based on temperature and the reflectivity of the main laser return light and feed them back to the laser module 2;

[0051] Melting determination units 1-4 are used to determine whether the processing area of ​​the workpiece has melted.

[0052] In this invention, laser module 2 outputs a composite laser, mainly comprising an auxiliary laser and a main laser. The main laser is an infrared fiber laser with a wavelength of 1050–1080 nm and an output beam diameter of 50–200 μm. The auxiliary laser is a blue semiconductor laser with a wavelength of 420–470 nm and an output beam diameter of 300–500 μm. The auxiliary laser is used to heat the surface of the workpiece to provide uniform preheating; the main laser is used to penetrate the workpiece and perform fine deep-cutting. The laser head of laser module 2 first outputs a high-power auxiliary laser to preheat the target area of ​​the workpiece, gradually increasing the temperature of the processing area and entering the preheating stage. During this stage, in addition to the high-power auxiliary laser, the laser also simultaneously outputs a lower-power main laser, which, together with the auxiliary laser, irradiates the processing area. In the preheating stage of this embodiment, the auxiliary laser accounts for 70%–90% of the total output power, and the main laser accounts for 10%–30% of the total output power.

[0053] The reason for the higher auxiliary laser power and lower main laser power output during the preheating stage is that, for most metal materials, the absorption rate of blue light is much greater than that of infrared light at room temperature or below the melting point (see Figure 6a). Therefore, the power of the auxiliary laser (blue light) needs to be increased during the preheating stage to rapidly heat and melt the metal surface. Since the absorption rate of infrared light is low and the reflectivity is high before melting (see Figures 6a and 6b), reducing the power of the infrared laser during the preheating stage can effectively reduce the damage of reflected light to the laser and achieve a higher total laser output.

[0054] To ensure precise temperature control in the processing area, temperature detection module 3-1 and reflected light detection module 3-2 monitor the temperature of the processing area and the reflectivity of the main laser in the reflected light in real time, and feed the data back to control module 1. Control module 1 assesses the state of the processing area based on real-time data of temperature changes and reflected light reflectivity, and adjusts the laser processing parameters. Laser control module 2 outputs the corresponding laser based on the processing parameters. Through these dynamic adjustments, control module 1 can effectively control the preheating rate, avoiding excessively long preheating times and thus preventing a reduction in processing efficiency.

[0055] Once the control module 1 determines, based on temperature and reflectivity, that the surface of the processing area has melted and formed a molten pool, the surface melting stage begins. During this stage, the control module 1 controls the laser module 2 to significantly increase the output power of the main laser to enhance the processing effect, while simultaneously reducing the power output of the auxiliary laser. At this time, the main laser will perform deep and fine processing on the workpiece based on the molten pool, while the auxiliary laser is used to help maintain the stability of the molten pool. In the surface melting stage of this embodiment, the main laser accounts for 70%-90% of the initial total output power, and the auxiliary laser accounts for 10%-30% of the initial total output power. Because the beam of the auxiliary laser is larger than that of the main laser, a larger surface molten pool helps reduce the sputtering effect generated when the main laser penetrates deeper into the processing area.

[0056] Temperature detection module 3-1 and reflected light detection module 3-2 continuously monitor the temperature of the molten pool and the reflectivity of the main laser's reflected light to ensure the molten pool remains stable. Control module 1 adjusts the laser output in real time based on feedback data to prevent overheating of the molten pool, which could lead to vaporization or the formation of impurity compounds, factors that affect processing quality.

[0057] When the laser head of laser module 2 illuminates the processing area of ​​the workpiece, a portion of the laser light is reflected by the surface of the processing area and returns to the laser head along the original laser path; this portion of the laser light is called the reflected light. Since the absorption rate of infrared laser light by metallic materials varies significantly near their melting point (see Figure 7), the reflectivity of the main laser can be calculated by detecting the reflected light, thus determining whether the metallic material has melted. The reflected light detection module 3-2 detects and calculates the reflectivity of the main laser in the reflected light, not the reflectivity of the auxiliary laser within the reflected light.

[0058] The reflected light detection module 3-2 is integrated with the laser head of laser module 2 (i.e., at the laser output position). This ensures that regardless of the angle at which the laser head of laser module 2 illuminates the processing area of ​​the workpiece, the reflected light detection module 3-2 can detect the reflectivity of the main laser beam. Alternatively, the reflected light detection module 3-2 can be installed on the side of the laser path of the main and auxiliary lasers, using a beam splitter or reflector to separate the reflected light from the main laser beam and guide it into the reflected light detection module 3-2. Compared to the other installation position, directly integrating the laser head into laser module 2 allows for the use of existing laser system devices. Installing it on the side of the optical path may require additional complex optical path design, increasing cost and design complexity.

[0059] This invention installs a wavelength-selective filter in the reflected light detection module 3-2 to filter out the auxiliary laser in the reflected light, allowing only the main laser in the reflected light to pass through. Furthermore, since the reflected light follows the same path as the original composite laser, an optical isolator is used to separate the main laser reflected light and guide it to the reflected light detection module 3-2. The reflected light detection module 3-2 calculates the reflectivity of the main laser reflected light by comparing the intensity of the main laser in the reflected light with the intensity of the main laser output from the laser module 2.

[0060] The reason why this invention detects the reflectivity of reflected light instead of lasers with other reflection paths is as follows: The reflected light corresponds perfectly to the path of the laser incident on the workpiece processing area, and can directly reflect the optical characteristics (reflectivity) of the processing area. Once the surface of the processing area melts from a solid to a liquid state, the reflectivity of the reflected light will change significantly, and this transition process can be reflected in real time. During laser processing, slag and smoke may be generated on the workpiece surface, which will scatter the laser and complicate the reflection paths of other lasers. If relying on lasers with other reflection paths, the control module 1 may be interfered with, making it difficult to quickly and accurately determine the state changes of the processing area. In addition, the detection based on reflected light can directly utilize existing laser system devices, and the reflected light detection module 3-2 is directly integrated into the laser head of the laser module 2. Other reflection paths may require additional complex optical path design to capture reflected light from other directions, increasing cost and design difficulty.

[0061] The device of the present invention can automatically identify the material type of the workpiece (such as copper, iron, aluminum, ceramics, glass, etc.) so that the control module 1 can initially set the initial processing parameters of the preheating stage and the surface melting stage according to the material type and specific processing requirements, and at the same time provide a basis for the dynamic parameter adjustment of each stage.

[0062] Material identification and initial parameter setting process:

[0063] The control module 1 integrates a material database that stores data on the reflectivity characteristics of common workpiece materials under different temperatures, laser wavelengths, and incident angles, particularly the reflectivity characteristics near the melting point. This database is a key tool for material identification; by comparing the characteristic data, it can accurately match material types.

[0064] After the workpiece is fixed and before preheating begins, the control module 1 controls the laser module 2 to output a single laser beam of appropriate wavelength (such as a 1064nm laser) and irradiate the workpiece surface at a vertical angle (0° incident). The reflected light detection module 3-2 measures the reflectivity data of the reflected light in real time and feeds the data back to the control module 1.

[0065] Laser module 2 then adjusts the laser incident angle (e.g., 15°, 30°) and records the reflected light reflectance under different incident angle conditions, forming a set of reflectance characteristic parameters. These parameters are compared with reflectance characteristic curves in the material database to preliminarily identify the material type of the workpiece.

[0066] If multiple materials with similar reflectivity characteristics are found in the initial identification stage, the control module 1 will control the laser module 2 to switch the wavelength of the laser (such as switching to 532nm or 1550nm), repeat the above angle test process, record the reflectivity characteristics under the new wavelength conditions, so as to further narrow down the range of candidate materials and finally determine the unique material type.

[0067] Once the material type is determined, the control module 1 sets the initial processing parameters for the preheating and surface melting stages based on the identification results. The initial processing parameters for the preheating stage are then transmitted to the laser module 2, which outputs a composite laser to begin preheating.

[0068] As the temperature in the processing area gradually increases, the retroreflectance detection module 3-2 records the reflectance changes under various temperature conditions in real time. The control module 1 combines this data with the retroreflectance data recorded before preheating under different laser wavelengths and incident angles to further verify the accuracy of the material identification results or correct possible identification deviations, and dynamically optimize and adjust the processing parameters accordingly.

[0069] When the temperature of the processing area approaches the material's melting point, the surface begins to melt, and the processing enters the surface melting stage. At this time, the reflectivity of the main laser's reflected light changes significantly, making it easiest for control module 1 to accurately identify the workpiece's material type based on the reflectivity. If the workpiece's material type remains unchanged, control module 1 continues to use the initial processing parameters from the surface melting stage to guide subsequent processing. If the material type changes, control module 1 will readjust the processing parameters to ensure that the processing is adapted to the characteristics of the new material.

[0070] In some other optimized embodiments, a scattered laser analysis module is also provided, which can further detect the data on the intensity and distribution characteristics of scattered light caused by the laser on the surface of the processing area of ​​the workpiece, and feed it back to the control module 1. The control module 1 combines the aforementioned reflected light reflectance data to further determine the material type of the workpiece.

[0071] After accurately identifying the material type of the workpiece, the control module 1 sets the initial processing parameters for the preheating stage and the surface melting stage, and sets the conditions for optimizing and adjusting the processing parameters according to the specific processing requirements (such as deep processing, surface treatment, or complex shape processing).

[0072] The processing parameters set by the control module 1 for each stage include at least one of the following: total output power of the main laser and auxiliary laser, power ratio, laser scanning speed, pulse width, pulse frequency, peak power, incident angle, average power, and duty cycle.

[0073] The criteria for optimizing and adjusting processing parameters include: a first threshold representing the lowest temperature change rate during the preheating stage, the longest preheating time, a second threshold used to determine whether the surface melting stage has begun by observing the rate of change in reflected light reflectance, a reflected light reflectance-temperature curve related to the workpiece material type, and the target temperature range of the processing area during the surface melting stage.

[0074] The control module 1 accesses historical processing data, which contains optimal processing parameters for the same or similar materials under different processing requirements. This historical data also records common problems encountered during processing (such as overheating, vaporization, or unstable molten pools) and corresponding parameter adjustment strategies, providing a reference for dynamically optimizing processing parameters in both stages. Furthermore, the control module 1 collects relevant information about the current processing environment, such as the initial temperature of the workpiece, ambient temperature and humidity, and the performance status of the laser module 2. This data directly affects energy transfer and thermal effects during processing. After comprehensively considering material type, processing requirements, historical data, and environmental factors, the control module 1 uses optimization algorithms to calculate the initial processing parameters for each stage to ensure a balance between efficiency and processing quality in each stage (preheating stage and surface melting stage). The control module 1 then transmits the generated optimal initial processing parameters to the laser module 2 as the initial processing parameters for the preheating and surface melting stages.

[0075] By combining material type, processing requirements, historical processing data, and real-time environmental factors, the control module 1 can not only set initial processing parameters for each stage, ensuring efficient and stable operation from the start of processing and reducing debugging time and resource waste, but also provide a basis for judgment and corresponding adjustment strategies for subsequent dynamic adjustment of processing parameters, improving the stability of processing implementation. This comprehensive optimization strategy can significantly improve processing efficiency, ensure the stability of processing quality, and effectively reduce processing defects caused by improper parameter settings.

[0076] Laser module 2 first outputs auxiliary and main lasers based on the initial processing parameters of the preheating stage to preheat the processing area of ​​the workpiece. During the preheating process, control module 1 monitors the temperature change rate of the processing area in real time and determines whether it is below the set first threshold. If the temperature change rate is below the threshold, it indicates that the auxiliary laser power may be too low, the laser scanning speed may be too fast, or other reasons may be causing insufficient temperature rise. At this time, control module 1 increases the output power of the auxiliary laser, decreases the laser scanning speed, increases the laser duty cycle, or adjusts other processing parameters to increase the heating rate.

[0077] Simultaneously, the control module 1 calculates the rate of reflectivity change based on the real-time detection results of the reflected light reflectivity and generates an actual temperature-reflectivity curve. The control module 1 monitors whether the rate of reflectivity change exceeds a preset second threshold, or judges the characteristics of the reflected light reflectivity-temperature curve to identify whether a significant inflection point has occurred. Typically, when a workpiece approaches its material melting point, the reflected light reflectivity decreases rapidly and tends to stabilize, forming a significant "inflection point." When the reflectivity curve changes from a slow decrease to a rapid decrease and stabilizes near a certain value, it indicates that the processed area is approaching its melting point, at which point the reflected light reflectivity changes significantly. If the rate of change of the reflected light reflectivity exceeds the threshold and an inflection point is identified, the control module 1 determines that the processed area of ​​the workpiece has entered the surface melting stage, and the preheating stage ends.

[0078] In addition, the control module 1 also determines whether the preheating time exceeds the set maximum preheating time. If, within the maximum preheating time, the control module 1 detects that the processing area has entered the surface melting stage, it compares the actual reflected light reflectivity-temperature curve with the reflected light reflectivity-temperature curve corresponding to the workpiece material type in the material database to verify whether the workpiece material type automatically determined before preheating is correct. If the material type is incorrectly determined, the control module 1 will search the material database again for a material that matches the actual reflected light reflectivity-temperature curve and update the processing parameters and target temperature range of the surface melting stage according to the new material type. At this time, the control module 1 discards the original parameter data, saves the updated parameter data, and sends the updated processing parameters to the laser module 2. If the material type is correct, the control module 1 directly sends the initial processing parameters of the surface melting stage set before preheating to the laser module 2.

[0079] If the preheating time exceeds the set maximum preheating time, but the control module 1 has not yet detected the entry into the surface melting stage, the control module 1 will discard the original initial processing parameters for the surface melting stage and take the following measures to accelerate the temperature rise: increase the output power of the auxiliary laser, reduce the laser scanning speed, or adjust the processing parameters to increase the rate of temperature rise in the processing area. Once the processing area is detected to have entered the surface melting stage, the control module 1 will reconfirm the workpiece material type based on the actual generated rate of change of reflected light reflectance-temperature curve, and update the processing parameters and target temperature range.

[0080] During the surface melting stage, the processing area melts from a solid state to a liquid state, forming a molten pool. At this time, the control module 1 will determine in real time whether the molten pool temperature is within the newly set target temperature range. If the temperature exceeds the target range, the control module 1 will take the following measures to reduce the molten pool temperature: increase the laser scanning speed, reduce the laser duty cycle, or reduce the power of the main laser and / or auxiliary laser.

[0081] If the molten pool temperature is lower than the target range, the control module 1 will increase the main laser power, reduce the scanning speed, increase the duty cycle, or adjust other processing parameters to increase the molten pool temperature.

[0082] Furthermore, during the surface melting stage, the control module 1 continuously monitors the reflected light reflectance to ensure it matches the stored reflected light reflectance-temperature curve. If an anomaly is detected, the control module 1 will readjust the processing parameters. If the anomaly persists after adjustment, the system will issue an alarm to prompt manual intervention by the operator, who will then confirm the problem and input new processing parameters. The control module 1 will save the manually input parameter data and the anomaly data for AI learning, for future reference.

[0083] In summary, through the above, this embodiment can monitor the changes in temperature and reflectivity of the processing area throughout the entire process, automatically identify the material type of the workpiece and confirm the corresponding laser processing parameters, and continuously adjust the workpiece material judgment and processing parameters based on the actual situation during the processing to ensure the high efficiency and stability of the workpiece processing process.

[0084] In this embodiment, the laser module 2 includes a series of key components connected in sequence, as shown in Figure 3: a semiconductor pump source 2-1, a high-reflectivity grating 2-2, a ytterbium-doped gain fiber 2-3, a low-reflectivity grating 2-4, a cladding optical stripper 2-5, and a transmission fiber 2-6. These components work together to ensure the generation, modulation, transmission, and final output of the laser.

[0085] Semiconductor pump source 2-1 is the core component of laser module 2, containing three semiconductor chips of different wavelengths, used for outputting auxiliary laser, pump light, and indicator light, respectively. At least one of each of the three wavelengths is included in semiconductor pump source 2-1.

[0086] Blue light semiconductor chip with wavelength of 420-470nm: used for outputting auxiliary laser.

[0087] 650nm wavelength red light semiconductor chip: outputs indicator light to facilitate positioning and alignment of the processing area.

[0088] Pump light semiconductor chip with wavelength of 915nm or 976nm: used to output pump light that provides excitation energy to ytterbium-doped gain fiber, which is then converted into main laser.

[0089] The semiconductor pump source 2-1 has three positive and negative pins on the outside. The three positive and negative pins control the light output of the semiconductor chip of three different wavelengths. The power of the laser output by the semiconductor chip of the corresponding wavelength is changed by changing the voltage and current input to the positive and negative pins.

[0090] In another embodiment of the present invention, the output power of the corresponding laser (indicator laser, auxiliary laser, and pump laser) can also be controlled by controlling the number of semiconductor chips of each wavelength.

[0091] Inside the semiconductor pump source 2-1, each semiconductor chip has a corresponding high-reflectivity mirror, forming a combination. Each semiconductor chip and mirror combination is arranged in a stepped manner, i.e., layered along the optical path, with each optical path moving up or down layer by layer. The laser emitted by each semiconductor chip is guided by its corresponding high-reflectivity plane mirror to a focusing lens or mirror, forming parallel light composed of multiple beams.

[0092] The mirrors corresponding to the 420-470nm blue light semiconductor chip and the 650nm red light semiconductor chip guide and reflect the auxiliary laser and indicator light to the central region of the parallel light. The mirrors corresponding to the 915nm or 976nm pump light semiconductor chip guide and reflect the pump light to the peripheral region of the parallel light.

[0093] Finally, the parallel light composed of multiple beams is focused and coupled into the output optical fiber of the semiconductor pump source through a focusing lens group or a reflecting mirror. The input end of the output optical fiber of the semiconductor pump source is an end cap.

[0094] If the output fiber of the semiconductor pump source has a two-layer structure, consisting only of a cladding and a core, then the focusing lens couples the pump light, auxiliary laser, and indicator light from the parallel beam into its cladding. If the output fiber of the semiconductor pump source has a three-layer structure, consisting of an outer cladding, an inner cladding, and a core, then the focusing lens couples the auxiliary laser and indicator light into the inner cladding of the output fiber, and also couples the pump light into the inner cladding. The output fiber of the semiconductor pump source then transmits the light beam to the gain fiber 2-3 through the inner cladding.

[0095] In this embodiment, the pump light and the auxiliary laser are integrated into the semiconductor pump source 2-1 by spatial coupling, which saves the beam combiner and greatly reduces the overall size.

[0096] In another embodiment of the invention, the laser module 2 has multiple semiconductor pump sources 2-1, which are combined and transmitted to the gain fiber 2-3 via fiber combiner coupling or spatial coupling. In the gain fiber 2-3, pump light with wavelengths of 915 nm or 976 nm is absorbed by the gain medium in the fiber core and converted into a main laser (infrared laser) with wavelengths of 1050–1080 nm, which is then transmitted within the fiber core. The main laser is transmitted to the low-reflection grating 2-4 where it is partially reflected and transmitted.

[0097] A high-reflectivity grating 2-2 is used to reflect the main laser back to the ytterbium-doped gain fiber 2-3. In this way, the main laser is repeatedly reflected and amplified within the ytterbium-doped gain fiber 2-3. The high-reflectivity grating 2-2 uses a reflection range of approximately 1050–1080 nm, with a reflectivity >99%.

[0098] Figure 8 shows the absorption (solid line) and emission (dashed line) spectra of ytterbium-doped gain fiber for different wavelengths. Ytterbium-doped gain fiber 2-3, by absorbing pump light at wavelengths of 915 nm or 976 nm, excites ytterbium-doped ions to a high-energy state, and then emits a main laser beam at 1050-1080 nm, which propagates in the fiber core. The absorption cross-section (solid line) on the Y-axis in Figure 8 represents the absorption capability of ytterbium-doped ions for photons of specific wavelengths, with peaks at 915 nm and 976 nm, indicating that the pump light absorption efficiency is highest at these wavelengths. The emission cross-section (dashed line) on the Y-axis represents the radiation capability of ytterbium-doped ions for specific wavelengths, mainly concentrated in the 1030-1080 nm range, where 1050-1080 nm is the operating wavelength band for the main laser output.

[0099] Low-reflectivity gratings 2-4 are used to control the output of the main laser, allowing a small portion of the main laser to leak, thus forming a stable laser output. The low-reflectivity gratings 2-3 utilize the reflection range of approximately 1050–1080 nm, with a reflectivity between 3% and 30%.

[0100] After passing through the low-reflection grating, the laser enters the cladding optical stripper 2-5, which has a three-layer structure consisting of a fiber core, inner cladding, and outer cladding, as shown in Figure 4. It is used to strip the reflected light from the cladding and excess pump light that is not absorbed by the ytterbium-doped gain fiber, ensuring the stable operation of the laser module 2.

[0101] The main laser, converted from the absorbed pump light, propagates in the core of the cladding optical stripper 2-5. Excess unabsorbed pump light, auxiliary laser, indicator light, and return light propagate in the inner cladding of the cladding optical stripper 2-5. However, the outer cladding of the cladding optical stripper 2-5 has a special surface structure design that guides the excess pump light and return light from the inner cladding to the outer cladding for effective stripping, removing them from the system. The auxiliary laser and indicator light are not stripped and enter the inner cladding of the transmission fiber along the inner cladding of the cladding optical stripper 2-5, while the main laser enters the core of the transmission fiber 2-6 along the core of the cladding optical stripper 2-5.

[0102] Fiber 2-6 transmits the main laser, auxiliary laser, and indicator light to the quartz end cap at the tail end for final output. The spot size of the main laser output through the quartz end cap is smaller than that of the auxiliary laser.

[0103] In this embodiment, the NA value at the output end of the transmission fiber 2-6 is greater than or equal to the NA value at the input end. This is because a smaller NA value at the input end limits the incident angle of the laser beam exiting the cladding stripper 2-5, ensuring that only the core laser beam enters the transmission fiber 2-6 for transmission, while other light removed by the outer cladding of the cladding stripper 2-5 does not enter the transmission fiber 2-6. Simultaneously, it prevents the core laser beam entering the transmission fiber 2-6 from spreading due to an excessively large transmission angle, thus avoiding laser energy loss. Conversely, a larger NA value at the output end of the transmission fiber 2-6 allows for the emission of beams at larger angles, ensuring that the laser beam can exit smoothly from the end of the fiber.

[0104] In this embodiment, the dimensions of all fiber cores in laser module 2 range from 10 μm to 50 μm, and the dimensions of the cladding range from 125 μm to 1500 μm. Except for the cladding strippers 2-5, all optical fibers in the connecting components of laser module 2 can be either three-layered or two-layered. The main laser is transmitted in the fiber core, while the auxiliary laser and indicator light are transmitted in the inner cladding.

[0105] In summary, the control module 1 of this invention adjusts the output power of the laser module 2 in real time based on the reflected light reflectivity and temperature parameters fed back by the workpiece status inspection module 3. This significantly improves the laser utilization rate during processing, avoids resource waste caused by excessive laser output, and effectively reduces the generation of reflected light. The reflected light detection module 3-2 equipped in the system can separate and guide the reflected light into its interior, preventing it from flowing back to the laser module 2. The cladding light stripper 2-5 inside the laser module 2 further strips away excess pump light and reflected light, thereby protecting the core components of the laser module 2 and improving its operational stability and lifespan. The overall laser device design of this invention not only improves processing efficiency but also significantly reduces the risk of damage to the laser module 2 caused by reflected light.

[0106] Exemplary methods

[0107] Accordingly, embodiments of the present invention also provide a method for anti-backflow of high-power fiber lasers, as shown in Figure 5, including:

[0108] S501: Detect the status of the processing area of ​​the workpiece.

[0109] S502: Set processing parameters based on the state of the processing area.

[0110] S503: The laser generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser. The auxiliary laser is used to preheat and / or melt the surface of the processing area, and the main laser is used to perform deep processing on the processing area.

[0111] S504: If no melting occurs in the processing area, reduce the output power of the main laser.

[0112] S505: If melting occurs in the processing area, increase the output power of the main laser.

[0113] The state of the processing area includes:

[0114] Temperature of the processing area on the workpiece and / or reflectivity of the main laser reflected light from the processing area.

[0115] Before preheating the processing area, the workpiece is irradiated with lasers of different incident angles and / or different wavelengths; before preheating and at the beginning of the surface melting stage, the reflectivity data of the main laser reflected light in the processing area is collected; by analyzing the reflectivity of the main laser reflected light or by combining the temperature detection module 3-1 to detect the temperature of the processing area on the workpiece, the specific material type of the workpiece is identified before preheating, and the identification results are corrected at the beginning of the surface melting stage.

[0116] The material database stores reflectivity data of common materials at different temperatures, especially reflectivity data near the melting point; the measured workpiece surface temperature and reflectivity of the main laser reflected light are compared with the material properties in the material database, and the closest material type is matched according to the characteristic curve of reflectivity changing with temperature.

[0117] Based on the processing requirements and the material type of the workpiece identified before preheating, corresponding initial processing parameters are set for the preheating stage and the surface melting stage. The initial processing parameters for each stage include at least one of the following: total output power, laser scanning speed, power ratio of main laser to auxiliary laser, pulse width, pulse frequency, peak power, average power, and duty cycle.

[0118] Based on the temperature of the processing area and the reflectivity of the main laser reflected light, it is determined whether the processing area is currently in the preheating stage or the surface melting stage. At the beginning of the preheating stage, the laser outputs laser according to the initial processing parameters of the preheating stage to preheat the processing area of ​​the workpiece. At the beginning of the surface melting stage, the initial processing parameters of the surface melting stage are adjusted based on the workpiece material type correction result. During the process of each stage, the processing parameters are dynamically adjusted according to the real-time monitored temperature of the processing area and the reflectivity of the main laser reflected light, and fed back to the laser.

[0119] The conditions for adjusting the processing parameters are determined based on the material type and processing requirements of the workpiece, including: the first threshold, the longest preheating time, the second threshold, the reflectivity-temperature curve of the workpiece material, and the target temperature range of the processing area during the surface melting stage.

[0120] During the preheating stage, the auxiliary laser accounts for 70%-90% of the total output power, while the main laser accounts for 10%-30% of the total output power.

[0121] During the surface melting stage, the main laser accounts for 70%-90% of the total output power; the auxiliary laser accounts for 10%-30% of the total output power.

[0122] During the preheating stage, if the rate of temperature change in the processing area is lower than the first threshold, or if the preheating time exceeds the initial preheating time and the surface melting stage has not yet been detected, the power of the auxiliary laser is increased or the scanning speed is reduced.

[0123] The criteria for determining whether the processing area has entered the surface melting stage are: if the rate of change of the reflectivity of the main laser reflected light exceeds the second threshold; or if the actual change curve of the reflectivity of the main laser reflected light versus temperature shows a significant inflection point.

[0124] The surface melting stage also includes the following steps: determining whether the temperature of the processing area exceeds the target temperature range; if it exceeds the target temperature range, simultaneously reducing the total power of the main laser and the auxiliary laser, increasing the scanning speed, and reducing the pulse duty cycle to avoid overheating and metal splashing; if it is below the target temperature range, increasing the power of the main laser, reducing the scanning speed, and increasing the pulse duty cycle.

[0125] A module for detecting the reflectivity of the main laser's reflected light is installed on the side of the laser paths of the main and auxiliary lasers, and the main laser's reflected light is separated from the optical path using a beam splitter or reflector; alternatively, the module for detecting the reflectivity of the main laser's reflected light is installed at the output positions of the main and auxiliary lasers, and an optical isolator is used to separate the main laser's reflected light; a wavelength-selective filter is installed in the module for detecting the reflectivity of the main laser's reflected light, allowing only the main laser light in the reflected light to pass through. The reflectivity is calculated by calculating the ratio of the main laser intensity to the intensity of the main laser's reflected light.

[0126] The laser is provided with: a semiconductor pump source, a high-reflection grating, a ytterbium-doped gain fiber, a low-reflection grating, a cladding optical stripper, and a transmission fiber, connected in sequence, wherein:

[0127] The semiconductor pump source outputs the auxiliary laser, pump light, and indicator light;

[0128] The high-reflectivity grating reflects the main laser back to the ytterbium-doped gain fiber;

[0129] The ytterbium-doped gain fiber converts the pump light into the main laser and transmits the main laser in the fiber core, while transmitting the auxiliary laser and the indicator light in the inner cladding.

[0130] The low-reflectivity grating controls the output of the main laser;

[0131] The cladding light stripper strips away excess unabsorbed pump light and return light, and transmits the main laser, auxiliary laser, and indicator light;

[0132] The transmission optical fiber transmits the main laser, auxiliary laser, and indicator light to the quartz end cap at the tail end for final output.

[0133] The semiconductor pump source includes three types of semiconductor chips with different wavelengths:

[0134] The auxiliary laser is output by a 420-470nm blue light semiconductor chip;

[0135] The indicator light is output by a 650nm red light semiconductor chip, which facilitates positioning.

[0136] The pump light is output by a 915nm or 976nm pump light semiconductor chip;

[0137] The semiconductor pump source is externally controlled by three positive and negative pins, which control the light output of three different wavelength semiconductor chips. The light emitted by the three wavelength semiconductor chips is coupled into the output optical fiber of the semiconductor pump source via spatial optical coupling. The power of the laser output from the semiconductor chips in the laser is controlled by changing the voltage and current applied to the pins of the semiconductor pump source or by changing the number of semiconductor chips outputting the laser.

[0138] The process of coupling the light emitted by the three wavelength semiconductor chips into the output optical fiber of the semiconductor pump source via spatial optical coupling specifically includes: the laser emitted by each semiconductor chip changes the beam propagation direction through a high reflectivity plane mirror to form parallel light composed of multiple beams; each set of reflectors is arranged in a stepped manner, that is, arranged in layers in the optical path direction, with each set of optical paths moving up or down layer by layer; and each laser path is focused and coupled into the output optical fiber of the semiconductor pump source through a focusing lens group or a reflector.

[0139] The mirrors corresponding to the 420-470nm blue light semiconductor chip and the 650nm red light semiconductor chip reflect the auxiliary laser and the indicator light to the central region of the parallel light; the mirrors corresponding to the 915nm or 976nm pump light semiconductor chip reflect the pump light to the peripheral region of the parallel light.

[0140] The output fiber of the semiconductor pump source is a triple-clad laser, including a core, an inner cladding, and an outer cladding. The step of focusing and coupling each laser beam into the output fiber of the semiconductor pump source through a focusing lens group further includes: coupling the auxiliary laser and the indicator light into the inner cladding of the output fiber through a focusing lens; and coupling the pump light into the inner cladding of the output fiber through a focusing lens.

[0141] The input end of the optical fiber connected to the semiconductor pump source is an end cap.

[0142] The high and low reflective gratings adopt the reflection range of 1050-1080nm, with the high reflective grating having a reflectivity of >99% and the low reflective grating having a reflectivity between 3% and 30%.

[0143] The laser has multiple semiconductor pump sources, which transmit the laser beam to the high-reflectivity grating via fiber coupling or spatial coupling.

[0144] The output fiber of the semiconductor pump source includes a cladding and a core, and each laser beam is focused and coupled into the cladding of the output fiber of the semiconductor pump source by a focusing lens group or a reflector.

[0145] The NA value at the output end of the transmission optical fiber is greater than or equal to the NA value at the input end.

[0146] Based on the material type and processing requirements of the workpiece, and combined with the corresponding historical processing data, the optimal parameters are comprehensively optimized and used as the initial processing parameters for each stage.

[0147] The spot size of the main laser output through the quartz end cap at the tail is smaller than that of the auxiliary laser.

[0148] The dimensions of all fiber cores in the laser range from 10 μm to 50 μm, and the dimensions of all fiber claddings range from 125 μm to 1500 μm.

[0149] While the spirit and principles of the invention have been described with reference to several specific embodiments, it should be understood that the invention is not limited to the disclosed specific embodiments, and the division of aspects does not imply that features in these aspects cannot be combined for benefit; such division is merely for ease of description. The invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A high-power fiber laser device with anti-return capability, comprising a control module, a laser module, and a workpiece status inspection module; The workpiece status inspection module detects the status of the workpiece's processing area; The control module sets processing parameters based on the status detected by the workpiece status inspection module. The laser module generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser. The auxiliary laser is used to preheat and / or melt the surface of the processing area, and the main laser is used to perform deep processing on the processing area. When the workpiece status inspection module detects that the processing area has not melted, the control module reduces the output power of the main laser; When the workpiece status inspection module detects that the processing area has melted, the control module increases the output power of the main laser.

2. The apparatus according to claim 1, wherein the workpiece status inspection module 3 further comprises: The temperature detection module is used to detect the temperature of the processing area on the workpiece throughout the entire process and feed it back to the control module. and / or The reflected light detection module is used to detect the reflectivity of the main laser reflected light in the processing area throughout the entire process and feed it back to the control module.

3. The apparatus according to claim 2, wherein, Before preheating the processing area, the laser module irradiates the workpiece with lasers of different incident angles and / or different wavelengths. The backlight detection module collects the reflectivity data of the main laser backlight in the processing area before preheating and when it just enters the surface melting stage, and feeds it back to the control module. The control module analyzes the reflectivity of the main laser return light or detects the temperature of the processing area on the workpiece by combining the temperature detection module. It identifies the specific material type of the workpiece before preheating and corrects the identification results at the beginning of the surface melting stage.

4. The apparatus according to claim 2 or 3, wherein, The control module sets corresponding initial processing parameters for the preheating stage and the surface melting stage according to the processing requirements and the material type of the workpiece identified before preheating. The initial processing parameters for each stage include at least one of the following: total output power, laser scanning speed, power ratio of main laser to auxiliary laser, pulse width, pulse frequency, peak power, average power, and duty cycle. The control module determines whether the processing area is currently in the preheating stage or the surface melting stage based on the feedback data from the temperature detection module and / or the backlight detection module. At the beginning of the preheating phase, the laser module outputs laser according to the initial processing parameters of the preheating phase to preheat the processing area of ​​the workpiece; At the start of the surface melting stage, the control module adjusts the initial processing parameters of the surface melting stage based on the workpiece material type correction result and feeds them back to the laser module; During each stage of the process, the control module dynamically adjusts the processing parameters based on the real-time monitored temperature of the processing area and the reflectivity of the main laser return light, and feeds the adjustments back to the laser module.

5. The apparatus according to claim 4, wherein, The control module also determines the conditions for adjusting the processing parameters based on the material type and processing requirements of the workpiece, specifically including: a first threshold, the longest preheating time, a second threshold, the reflectivity-temperature curve of the workpiece material, and the target temperature range of the processing area during the surface melting stage.

6. The apparatus according to claim 4, wherein during the preheating stage, The auxiliary laser accounts for 70%-90% of the total output power; The main laser accounts for 10%-30% of the total output power.

7. The apparatus according to claim 4, wherein during the surface melting stage, The main laser accounts for 70%-90% of the total output power; The auxiliary laser accounts for 10%-30% of the total output power.

8. The apparatus according to claim 5, wherein, During the preheating stage, if the rate of temperature change in the processing area is lower than the first threshold, or if the preheating time exceeds the initial preheating time and the surface melting stage has not yet been detected, the control module increases the power of the auxiliary laser or reduces the scanning speed and feeds this information back to the laser module.

9. The apparatus according to claim 5, wherein, The criteria for determining whether the processing area has entered the surface melting stage are: If the rate of change of reflectivity of the main laser reflected light exceeds the second threshold; or The actual change curve of the reflectivity of the main laser return light versus temperature showed a significant inflection point.

10. The apparatus of claim 5, wherein during the surface melting stage, the control module is further configured to: Determine whether the temperature of the processing area exceeds the target temperature range; If the target temperature range is exceeded, the total power of the main laser and the auxiliary laser will be reduced simultaneously, the scanning speed will be increased, and the duty cycle of the pulse will be reduced to avoid overheating and metal sputtering. If the temperature is below the target temperature range, the power of the main laser is increased, the scanning speed is reduced, and the pulse duty cycle is increased.

11. The apparatus according to claim 2, wherein, The reflected light detection module is installed on the side of the laser path of the main laser and the auxiliary laser. It uses a beam splitter or a reflector to separate the reflected light from the main laser in the optical path and guides the reflected light to the reflected light detection module; or The return light detection module is installed at the laser output position of the laser module, and uses an optical isolator to separate the main laser return light and guide it to the return light detection module; A wavelength-selective filter is installed in the returned light detection module to allow only the main laser in the returned light to pass through.

12. The apparatus according to claim 11, wherein, The reflected light detection module calculates the reflectivity by calculating the ratio of the main laser intensity to the main laser reflected light intensity.

13. The apparatus of claim 1, wherein the laser module further comprises: The semiconductor pump source, high-reflection grating, ytterbium-doped gain fiber, low-reflection grating, cladding stripper, and transmission fiber are connected in sequence, wherein: The semiconductor pump source is used to output the auxiliary laser, pump light, and indicator light; The high-reflectivity grating is used to reflect the main laser back to the ytterbium-doped gain fiber; The ytterbium-doped gain fiber is used to convert the pump light into the main laser and transmit the main laser in the fiber core, and to transmit the auxiliary laser and the indicator light in the inner cladding. The low-reflectivity grating is used to control the output of the main laser; The cladding light stripper is used to strip away excess pump light and return light that has not been absorbed, and to transmit the main laser, auxiliary laser and indicator light; The transmission optical fiber is used to transmit the main laser, auxiliary laser, and indicator light to the quartz end cap at the tail end for final output.

14. The apparatus of claim 13, wherein the semiconductor pump source comprises three wavelength semiconductor chips: 420-470nm blue light semiconductor chip: used to output the auxiliary laser; 650nm red light semiconductor chip: used to output the indicator light for easy positioning; 915nm or 976nm pump light semiconductor chip: used to output the pump light; The semiconductor pump source is controlled by three positive and negative pins to control the light output of three different wavelength semiconductor chips. The light emitted by the three wavelength semiconductor chips is coupled into the output optical fiber of the semiconductor pump source via spatial light coupling.

15. The apparatus according to claim 14, wherein, The power of the laser output by the semiconductor chips in the laser module can be controlled by changing the voltage and current applied to the semiconductor pump source pin or by changing the number of semiconductor chips that output the laser.

16. The apparatus of claim 14, wherein the light emitted by the three wavelength semiconductor chips is spatially coupled into the output optical fiber of the semiconductor pump source as follows: The laser emitted by each semiconductor chip changes the direction of beam propagation through a high-reflectivity plane mirror, forming parallel light composed of multiple beams; Each set of mirrors is arranged in a stepped manner, that is, in layers along the optical path, with each set of optical paths moving up or down layer by layer. Each laser beam is focused and coupled into the output fiber of the semiconductor pump source using a focusing lens group or a reflector.

17. The apparatus according to claim 16, wherein: The mirrors corresponding to the 420-470nm blue light semiconductor chip and the 650nm red light semiconductor chip reflect the auxiliary laser and the indicator light to the central region of the parallel light. The mirror corresponding to the 915nm or 976nm pump light semiconductor chip reflects the pump light to the peripheral region of the parallel light.

18. The apparatus of claim 17, wherein the output fiber of the semiconductor pump source is a triple-clad laser, comprising a core, an inner cladding, and an outer cladding, and the step of focusing and coupling each laser beam into the output fiber of the semiconductor pump source via a focusing lens group further comprises: The auxiliary laser and the indicator light are coupled into the inner cladding of the output optical fiber through a focusing lens; The pump light is coupled into the inner cladding of the output optical fiber through a focusing lens.

19. The apparatus of claim 18, wherein the input end of the optical fiber connected to the semiconductor pump source is an end cap.

20. The apparatus of claim 13, wherein the high and low reflective gratings adopt a reflection range of approximately 1050-1080 nm, the high reflective grating has a reflectivity >99%, and the low reflective grating has a reflectivity between 3% and 30%.

21. The apparatus of claim 13, wherein the laser module has a plurality of semiconductor pump sources that transmit laser light to the high-reflectivity grating via fiber coupling or spatial coupling.

22. The apparatus of claim 17, wherein the output fiber of the semiconductor pump source comprises a cladding and a core, and the laser beams are focused and coupled into the cladding of the output fiber of the semiconductor pump source by a focusing lens group or a reflector.

23. The apparatus of claim 13, wherein the NA value at the output end of the transmission optical fiber is greater than or equal to the NA value at the input end.

24. The apparatus according to claim 4, wherein the control module comprehensively optimizes the parameters based on the material type and processing requirements of the workpiece and in conjunction with the corresponding historical processing data to obtain the optimal parameters, which are used as the initial processing parameters for each stage.

25. The apparatus according to claim 4, wherein, The control module also includes: A materials database for storing reflectance data of common materials at different temperatures, especially reflectance data near the melting point; The material identification unit is used to compare the workpiece surface temperature measured by the temperature detection module and the reflectivity data measured by the backlight detection module with the material properties in the material database, and match the closest material type according to the characteristic curve of reflectivity changing with temperature. The parameter adjustment unit is used to adjust the processing parameters based on the temperature and the reflectivity of the main laser reflected light and then feed them back to the laser module. A melting determination unit is used to determine whether the processing area of ​​the workpiece has melted.

26. The apparatus according to claim 13, wherein, The spot size of the main laser output through the quartz end cap at the tail is smaller than that of the auxiliary laser.

27. The apparatus according to claim 13, wherein, The dimensions of all fiber cores in the laser module range from 10μm to 50μm. The dimensions of all fiber cladding in the laser module range from 125 μm to 1500 μm.

28. A method for preventing backtracking in a high-power fiber laser, comprising: Inspect the condition of the workpiece's machining area; Set processing parameters based on the state of the processing area; The laser generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser. The auxiliary laser is used to preheat and / or melt the surface of the processing area, and the main laser is used to perform deep processing on the processing area. If no melting occurs in the processing area, reduce the output power of the main laser; If melting occurs in the processing area, increase the output power of the main laser.

29. The method according to claim 28, wherein, The state of the processing area includes: Temperature of the processing area on the workpiece and / or reflectivity of the main laser reflected light from the processing area.

30. The method according to claim 29, wherein, Before preheating the processing area, irradiate the workpiece with lasers of different incident angles and / or different wavelengths; Before preheating and just as the surface melting stage begins, the reflectivity data of the main laser reflected light in the processing area is collected. By analyzing the reflectivity of the main laser's reflected light or by combining it with a temperature detection module to detect the temperature of the processing area on the workpiece, the specific material type of the workpiece can be identified before preheating, and the identification results can be corrected at the beginning of the surface melting stage.

31. The method according to claim 29 or 30, wherein, Based on the processing requirements and the material type of the workpiece identified before preheating, corresponding initial processing parameters are set for the preheating stage and the surface melting stage. The initial processing parameters for each stage include at least one of the following: total output power, laser scanning speed, power ratio of main laser to auxiliary laser, pulse width, pulse frequency, peak power, average power, and duty cycle. Based on the temperature of the processing area and the reflectivity of the main laser reflected light, it can be determined whether the processing area is currently in the preheating stage or the surface melting stage. At the beginning of the preheating stage, the laser outputs laser according to the initial processing parameters of the preheating stage to preheat the processing area of ​​the workpiece; At the start of the surface melting stage, the initial processing parameters of the surface melting stage are adjusted based on the workpiece material type correction results; During each stage of the process, the processing parameters are dynamically adjusted based on the real-time monitored temperature of the processing area and the reflectivity of the main laser's reflected light, and then fed back to the laser.

32. The method according to claim 31, wherein, The conditions for adjusting the processing parameters are determined based on the material type and processing requirements of the workpiece, including: the first threshold, the longest preheating time, the second threshold, the reflectivity-temperature curve of the workpiece material, and the target temperature range of the processing area during the surface melting stage.

33. The method according to claim 31, wherein during the preheating stage, The auxiliary laser accounts for 70%-90% of the total output power; The main laser accounts for 10%-30% of the total output power.

34. The method of claim 31, wherein during the surface melting stage, The main laser accounts for 70%-90% of the total output power; The auxiliary laser accounts for 10%-30% of the total output power.

35. The method according to claim 32, wherein, During the preheating stage, if the rate of temperature change in the processing area is lower than the first threshold, or if the preheating time exceeds the initial preheating time and the surface melting stage has not yet been detected, the power of the auxiliary laser is increased or the scanning speed is reduced.

36. The method according to claim 32, wherein, The criteria for determining whether the processing area has entered the surface melting stage are: If the rate of change of reflectivity of the main laser reflected light exceeds the second threshold; or The actual change curve of the reflectivity of the main laser return light versus temperature showed a significant inflection point.

37. The method of claim 32, further comprising the following steps during the surface melting stage: Determine whether the temperature of the processing area exceeds the target temperature range; If the target temperature range is exceeded, the total power of the main laser and the auxiliary laser will be reduced simultaneously, the scanning speed will be increased, and the duty cycle of the pulse will be reduced to avoid overheating and metal sputtering. If the temperature is below the target temperature range, the power of the main laser is increased, the scanning speed is reduced, and the pulse duty cycle is increased.

38. The method according to claim 29, wherein, A module for detecting the reflectivity of the main laser return light is installed on the side of the laser path of the main laser and the auxiliary laser, and the main laser return light is separated from the optical path using a beam splitter or a reflector; or A module for detecting the reflectivity of the main laser return light is installed at the output positions of the main laser and the auxiliary laser, and an optical isolator is used to separate the main laser return light. A wavelength-selective filter is installed in the module that detects the reflectivity of the main laser's reflected light, allowing only the main laser in the reflected light to pass through.

39. The method according to claim 38, wherein, The reflectivity is calculated by measuring the ratio of the intensity of the main laser to the intensity of the light returned by the main laser.

40. The method of claim 28, wherein the laser is provided with: a semiconductor pump source, a high-reflection grating, a ytterbium-doped gain fiber, a low-reflection grating, a cladding optical stripper, and a transmission fiber connected in sequence, wherein: The semiconductor pump source outputs the auxiliary laser, pump light, and indicator light; The high-reflectivity grating reflects the main laser back to the ytterbium-doped gain fiber; The ytterbium-doped gain fiber converts the pump light into the main laser and transmits the main laser in the fiber core, while transmitting the auxiliary laser and the indicator light in the inner cladding. The low-reflectivity grating controls the output of the main laser; The cladding light stripper strips away excess unabsorbed pump light and return light, and transmits the main laser, auxiliary laser, and indicator light; The transmission optical fiber transmits the main laser, auxiliary laser, and indicator light to the quartz end cap at the tail end for final output.

41. The method of claim 40, wherein the semiconductor pump source comprises three wavelength semiconductor chips: The auxiliary laser is output by a 420-470nm blue light semiconductor chip; The indicator light is output by a 650nm red light semiconductor chip, which facilitates positioning. The pump light is output by a 915nm or 976nm pump light semiconductor chip; The semiconductor pump source is controlled by three positive and negative pins to control the light output of three different wavelength semiconductor chips. The light emitted by the three wavelength semiconductor chips is coupled into the output optical fiber of the semiconductor pump source via spatial light coupling.

42. The method according to claim 41, wherein, The power of the laser output by the semiconductor chips in the laser can be controlled by changing the voltage and current applied to the semiconductor pump source pin or by changing the number of semiconductor chips that output the laser.

43. The method according to claim 41, wherein the light emitted by the three wavelength semiconductor chips is spatially coupled into the output optical fiber of the semiconductor pump source, specifically comprising: The laser emitted by each semiconductor chip changes the direction of beam propagation through a high-reflectivity plane mirror, forming parallel light composed of multiple beams; Each set of mirrors is arranged in a stepped manner, that is, in layers along the optical path, with each set of optical paths moving up or down layer by layer. Each laser beam is focused and coupled into the output fiber of the semiconductor pump source using a focusing lens group or a reflector.

44. The method according to claim 43, wherein: The mirrors corresponding to the 420-470nm blue light semiconductor chip and the 650nm red light semiconductor chip reflect the auxiliary laser and the indicator light to the central region of the parallel light. The mirror corresponding to the 915nm or 976nm pump light semiconductor chip reflects the pump light to the peripheral region of the parallel light.

45. The method according to claim 44, wherein the output fiber of the semiconductor pump source is a triple-clad laser, comprising a core, an inner cladding, and an outer cladding, and the step of focusing and coupling each laser beam into the output fiber of the semiconductor pump source using a focusing lens group further comprises: The auxiliary laser and the indicator light are coupled into the inner cladding of the output optical fiber through a focusing lens; The pump light is coupled into the inner cladding of the output optical fiber through a focusing lens.

46. ​​The method of claim 45, wherein the input end of the optical fiber connected to the semiconductor pump source is an end cap.

47. The method according to claim 40, wherein the high and low reflective gratings adopt a reflection range of around 1050-1080nm, the high reflective grating has a reflectivity >99%, and the low reflective grating has a reflectivity between 3% and 30%.

48. The method of claim 40, wherein the laser has a plurality of semiconductor pump sources that transmit laser light to the high-reflectivity grating via fiber coupling or spatial coupling.

49. The method of claim 44, wherein the output fiber of the semiconductor pump source comprises a cladding and a core, and the laser beams are focused and coupled into the cladding of the output fiber of the semiconductor pump source by a focusing lens group or a reflector.

50. The method of claim 40, wherein the NA value at the output end of the transmission optical fiber is greater than or equal to the NA value at the input end.

51. The method according to claim 31, wherein the optimal parameters are obtained by comprehensively optimizing the parameters based on the material type and processing requirements of the workpiece and the corresponding historical processing data, and are used as the initial processing parameters for each stage.

52. The method of claim 31, further comprising the following steps: Store reflectance data of common materials at different temperatures in a materials database, especially reflectance data near the melting point; The measured workpiece surface temperature and the reflectivity of the main laser reflected light are compared with the material properties in the material database. Based on the characteristic curve of reflectivity changing with temperature, the closest material type is matched.

53. The method according to claim 40, wherein, The spot size of the main laser output through the quartz end cap at the tail is smaller than that of the auxiliary laser.

54. The method according to claim 40, wherein, The dimensions of all fiber cores in the laser range from 10 μm to 50 μm; The dimensions of all fiber cladding in the laser range from 125 μm to 1500 μm.

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