A multi-wavelength nonlinear femtosecond laser processing method and system

Abstract

The present invention discloses a multi-wavelength nonlinear femtosecond laser processing method and system. The present invention uses multiple high-power femtosecond lasers to emit high-power femtosecond lasers of different wavelengths; accurately controls the optical path difference and group delay of the lasers emitted by each laser through an optical path difference and group delay control module; injects the multi-wavelength femtosecond laser into a three-dimensional displacement focusing module; and finally vertically injects the laser into the upper surface of the sample to be processed to complete the femtosecond laser processing. By precisely modulating the relative positions of the laser pulses of each wavelength in the time domain, the present invention can achieve dynamic nonlinear and precise control of the temperature field in the sample processing area, improve the efficiency, quality and processing depth of precision processing, and expand the application range of femtosecond laser precision processing.

Description

Technical Field

[0001] The present invention relates to the field of laser applications, and in particular to a multi-wavelength nonlinear femtosecond laser processing method and system. Background Art

[0002] Compared with traditional processing methods, laser processing has many advantages such as high processing efficiency, fast speed and good quality. It has broad application prospects and development space in the field of industrial manufacturing.

[0003] Compared to continuous laser processing, femtosecond laser processing offers higher peak energy and more ordered energy output. This means that femtosecond laser processing can process a wider range of materials, achieve greater processing depth, minimize thermal damage outside the processing area, achieve higher processing quality, and further enhance processing speed and efficiency.

[0004] Currently, the femtosecond laser processing field is dominated by solutions using single-wavelength solid-state laser sources. Compared with fiber femtosecond lasers, solid-state femtosecond lasers have a number of disadvantages, including large size, fragility, difficulty in maintenance, and high cost. Furthermore, existing technologies using single-wavelength lasers for processing also have numerous limitations. For example, they have poor adaptability to different materials, limiting processing to materials with high absorption rates within that wavelength band; the material heating method is linear, which is slow, and heat is easily transferred to the periphery of the processing area, resulting in poor processing quality; and they cannot actively and accurately modulate the local transient temperature field in the processing area.

[0005] Existing multi-wavelength (dual-wavelength) laser processing methods all rely on a single laser emitting fundamental frequency light and then frequency-doubling that fundamental frequency light. This approach improves upon the shortcomings of the single-wavelength laser processing method to a certain extent, but it does not completely overcome the limitations of the aforementioned issues.

[0006] In the prior art, the multi-wavelength laser processing device described in the "Multi-wavelength Laser Processing Device" includes a multi-wavelength laser emitting lasers of different wavelengths, a laser processing system, and a laser beam combining device. The laser processing system includes a galvanometer assembly, which includes a scanning galvanometer and a focusing mirror. The laser beam combining device includes a first dispersion compensation assembly, a second dispersion compensation assembly, a first reflector, a second reflector, and a first polychromatic beam combining mirror. The first dispersion compensation assembly includes a first right-angle mirror and a first prism for the first wavelength laser to pass through. The second dispersion compensation assembly includes a second right-angle mirror and a second prism for the second wavelength laser to pass through. The first reflector reflects the dispersion-compensated first wavelength laser and combines it with the dispersion-compensated second wavelength laser in the first polychromatic beam combining mirror. The combined laser beam is then reflected by the second reflector into the scanning galvanometer, focused by the focusing mirror, and then processed by the workpiece. Due to the lack of an optical path difference and group delay detector, the relative delays of the laser beams of different wavelengths cannot be changed, making high-precision material processing impossible. The three wavelengths used (red light, green light, and violet light) are fixed and difficult to adapt to the absorption characteristics of different materials (CN112091416A). Summary of the Invention

[0007] Based on this, the multi-wavelength nonlinear femtosecond laser processing method proposed in this paper can effectively overcome the above-mentioned problems. By using multiple femtosecond fiber lasers with different output wavelengths as the processing light source and by controlling the time domain of each laser, the method can improve the variety of processed materials and the processing accuracy, speed, depth, and quality.

[0008] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0009] A multi-wavelength nonlinear femtosecond laser processing method comprises the following steps:

[0010] S1. Using a group of high-power femtosecond lasers to generate multiple high-power femtosecond lasers having at least two different wavelengths;

[0011] S2, passing each high-power femtosecond laser beam obtained in step S1 through a pair of angle-adjustable thin film reflectors, and then combining the reflected light beams using a beam combiner;

[0012] S3, allowing the combined light beams obtained in step S2 to enter a beam splitter for splitting each high-power femtosecond laser beam into two paths: a signal light and an idle light;

[0013] S4, allowing the signal light obtained in step S3 to enter a photodetector, converting the optical signal into an electrical signal, and then passing it through an optical path difference and group delay detector to regulate the thin film mirror pair, thereby controlling the optical path difference and group delay of each high-power femtosecond laser and adjusting the idle light in step S3;

[0014] S5. The idle light adjusted in step S4 is passed through a beam focusing module. The focused laser is vertically irradiated onto the upper surface of the sample to be processed. The different effects of each femtosecond laser on the processed sample are used to control the nonlinear temperature field and finally complete the processing.

[0015] Furthermore, in step S1, the group of high-power femtosecond lasers includes two or more high-power femtosecond lasers that can output different wavelengths, and is used to generate multiple high-power femtosecond lasers including at least two different wavelengths.

[0016] Furthermore, the repetition frequency of high-power femtosecond lasers output by each high-power femtosecond laser is consistent, and the output power is adjustable.

[0017] Furthermore, in step S4, after the photodetector converts each signal light signal into an electrical signal, the optical path difference and group delay detector detects the relative time delay between each high-power femtosecond laser and calculates the optical path difference, thereby adjusting the tilt angle of each thin film reflector pair to compensate for the optical path difference of each high-power femtosecond laser, thereby achieving time domain regulation of the idle light;

[0018] After adjustment, the time for each laser to act on the sample surface is accurately allocated according to the actual application scenario, with an accuracy of the fs level.

[0019] Furthermore, in step S5, the beam focusing module is fixed on a three-dimensional displacement adjustment frame to form a three-dimensional displacement focusing module, which is used to change the relative position of the beam focus and the surface of the sample to be processed, adjust the spot size on the surface of the sample to be processed, and adapt to the processing requirements of different samples to be processed.

[0020] Furthermore, in step S5, the temperature field refers to the local temperature field of the sample to be processed when the laser is focused by the beam focusing module and irradiated on the sample to be processed, and the nonlinearity refers to the nonlinear heating method of the sample to be processed during the temperature rise period.

[0021] Furthermore, in step S5, the manner of regulating the nonlinear temperature field includes changing the output power of each high-power femtosecond laser.

[0022] Furthermore, in step S5, the nonlinear temperature field is regulated by controlling the optical path difference and group delay of high-power femtosecond lasers emitted by different high-power femtosecond lasers through an optical path difference and group delay control module.

[0023] Furthermore, in step S5, the method of regulating the nonlinear temperature field includes controlling the effective area of ​​the emitted laser on the surface of the sample to be processed by a three-dimensional displacement focusing module.

[0024] A multi-wavelength nonlinear femtosecond laser processing system includes a group of high-power femtosecond lasers, an optical path difference and group delay control module, and a three-dimensional displacement focusing module;

[0025] The group of high-power femtosecond lasers includes two or more high-power femtosecond lasers capable of outputting different wavelengths;

[0026] The optical path difference and group delay control module includes two sets of angle-adjustable thin film reflectors, a set of beam-splitting mirrors, a beam splitter, a photodetector, and an optical path difference and group delay controller;

[0027] The three-dimensional displacement focusing module includes a beam focusing module and a three-dimensional displacement adjustment frame;

[0028] A group of high-power femtosecond lasers generates multiple high-power femtosecond lasers with at least two different wavelengths. Each high-power femtosecond laser is reflected by two sets of angle-adjustable thin film reflectors, and then combined by a beam combiner to obtain a combined light beam. The combined light beam is incident on a beam splitter, which splits each high-power femtosecond laser into a signal light and an idle light.

[0029] The signal light enters the photodetector, which converts the optical signal into an electrical signal. Then, it passes through the optical path difference and group delay detector to achieve precise control of the thin film reflector, control the optical path difference and group delay of each high-power femtosecond laser, and adjust the idle light.

[0030] The adjusted idle light passes through the beam focusing module, and the focused laser is vertically irradiated onto the upper surface of the sample to be processed, finally completing the processing.

[0031] Compared with the prior art, the advantages of the present invention are:

[0032] The present invention uses multiple high-power femtosecond lasers that output lasers of different wavelengths and adopts a series of means to regulate the temperature field of the sample processing area, thereby improving the precision processing efficiency, quality and processing depth, and expanding the application scope of femtosecond laser precision processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the structure of a multi-wavelength nonlinear femtosecond laser processing system according to an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of a time sequence arrangement of pulses of different wavelengths within a single pulse period in an embodiment of the present invention;

[0035] Figure 3 Schematic diagram of the temperature rise curve of a material processed using a single-wavelength femtosecond laser within a single pulse period in an embodiment of the present invention;

[0036] Figure 4 Schematic diagram of the temperature rise curve of a material processed using a multi-wavelength femtosecond laser within a single pulse period in an embodiment of the present invention;

[0037] Figure 5 1 is a schematic diagram comparing the temperature rise curves of materials processed using a single-wavelength femtosecond laser and the temperature rise curves of materials processed using a multi-wavelength femtosecond laser during the entire processing process in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] Example:

[0040] A multi-wavelength nonlinear femtosecond laser processing method comprises the following steps:

[0041] S1. Using a group of high-power femtosecond lasers to generate multiple high-power femtosecond lasers having at least two different wavelengths;

[0042] The group of high-power femtosecond lasers includes two or more high-power femtosecond lasers that can output different wavelengths, and is used to generate multiple high-power femtosecond lasers including at least two different wavelengths.

[0043] The high-power femtosecond laser repetition frequency output by each high-power femtosecond laser is consistent, and the output power is adjustable.

[0044] S2, passing each high-power femtosecond laser beam obtained in step S1 through a pair of angle-adjustable thin film reflectors, and then combining the reflected light beams using a beam combiner;

[0045] S3, allowing the combined light beams obtained in step S2 to enter a beam splitter for splitting each high-power femtosecond laser beam into two paths: a signal light and an idle light;

[0046] S4, allowing the signal light obtained in step S3 to enter a photodetector, converting the optical signal into an electrical signal, and then passing it through an optical path difference and group delay detector to regulate the thin film mirror pair, thereby controlling the optical path difference and group delay of each high-power femtosecond laser and adjusting the idle light in step S3;

[0047] After the photodetector converts the optical signals of each channel into electrical signals, the optical path difference and group delay detector detects the relative time delay between the high-power femtosecond lasers of each channel and calculates the optical path difference, thereby adjusting the tilt angle of each thin film reflector pair to compensate for the optical path difference of each high-power femtosecond laser and realize time domain regulation of the idle light;

[0048] After adjustment, the time for each laser to act on the sample surface is accurately allocated according to the actual application scenario, with an accuracy of the fs level.

[0049] S5. The idle light adjusted in step S4 is passed through a beam focusing module. The focused laser is vertically irradiated onto the upper surface of the sample to be processed. The different effects of each femtosecond laser on the processed sample are used to control the nonlinear temperature field and finally complete the processing.

[0050] The beam focusing module is fixed on the three-dimensional displacement adjustment frame to form a three-dimensional displacement focusing module, which is used to change the relative position of the beam focus and the surface of the sample to be processed, adjust the spot size on the surface of the sample to be processed, and adapt to the processing requirements of different samples to be processed.

[0051] The temperature field refers to the local temperature field of the sample to be processed when the laser is focused by the beam focusing module and irradiated on the sample to be processed. The nonlinearity refers to the nonlinear heating method of the sample to be processed during the temperature rise period.

[0052] Methods for regulating the nonlinear temperature field include changing the output power of each high-power femtosecond laser.

[0053] The method for regulating the nonlinear temperature field includes controlling the optical path difference and group delay of high-power femtosecond lasers emitted by different high-power femtosecond lasers through an optical path difference and group delay control module.

[0054] The method of regulating the nonlinear temperature field includes controlling the effective area of ​​the emitted laser on the surface of the sample to be processed through a three-dimensional displacement focusing module.

[0055] In this embodiment, taking the processing of quartz crystal as an example, a multi-wavelength nonlinear femtosecond laser processing system, such as Figure 1 As shown, it includes a group of high-power femtosecond lasers A, an optical path difference and group delay control module B, and a three-dimensional displacement focusing module C;

[0056] The group of high-power femtosecond lasers A includes two or more high-power femtosecond lasers that can output different wavelengths, A1, A2, ..., A n There are n high-power femtosecond lasers, n≥2;

[0057] The optical path difference and group delay control module includes two sets of angle-adjustable thin film reflectors, a set of beam splitters, a beam splitter B4, a photodetector B5 and an optical path difference and group delay controller B6; 11 , B 12 ,……,B 1n B is the first group of n electrically adjustable thin film mirrors, n ≥ 2; 21 , B 22,……,B 2n B is the second group of n electrically adjustable thin film mirrors; 31 , B 32 ,……,B 3n is n beam combiners;

[0058] The three-dimensional displacement focusing module C includes a plane reflector C1, a beam focusing module C2, a three-dimensional displacement adjustment frame C3 and a sample to be processed C4;

[0059] Among the group of high-power femtosecond lasers, a high-power 1.0 μm wavelength femtosecond fiber laser and a high-power 2.0 μm wavelength femtosecond laser are selected as the first high-power femtosecond laser A1 and the first high-power femtosecond laser A2, respectively, based on the absorption spectrum, melting and boiling points, and other characteristics of the quartz crystal; wherein the output power of the first high-power femtosecond laser A1 is 1000 W, the repetition frequency is 1 GHz, and the pulse width is 300 fs; the output power of the second high-power femtosecond laser A2 is 200 W, the repetition frequency is 1 GHz, and the pulse width is 200 fs.

[0060] The first high-power femtosecond laser A1 enters the optical path difference and group delay control module B, and then passes through the first thin film reflector B with adjustable angle electronically. 11 、B 21 And the first beam combiner B has high transmittance for 1.0μm laser and high reflectivity for 2.0μm laser 31 The laser light outputted by the second high power femtosecond laser A2 passes through the second thin film reflector B with adjustable angle 12 、B 22 , the second beam combiner B with high reflectivity for 2.0μm laser 32 and the first beam combiner B which has high transmittance for 1.0μm laser and high reflectivity for 2.0μm laser 31 After the beam combining is completed, the combined light beam is incident on the beam splitter B4.

[0061] After the combined beam is split by the beam splitter B4, a beam of laser light is incident on the photodetector B5 as the signal light, and then transmitted to the optical path difference and group delay controller B6. The optical path difference and group delay controller B6 outputs an electrical control signal to adjust the angle of the electrically adjustable first thin film reflector B 11 、B 21 and the second thin film mirror B 12 、B 22 , so that the wavefront of 2.0μm femtosecond laser is 100fs ahead of 1.0μm femtosecond laser, the timing of the two laser pulses is arranged as follows Figure 2As shown, the solid line represents the single pulse energy distribution of a femtosecond fiber laser with an output wavelength of 2.0 μm and a repetition rate of 1 GHz, and the dotted line represents the single pulse energy distribution of a femtosecond fiber laser with an output wavelength of 1.0 μm and a repetition rate of 1 GHz.

[0062] The other laser beam split by the beam splitter B4 is incident on the three-dimensional displacement focusing module C as idle light. After being reflected by the plane mirror C1, it is incident on the beam focusing module C2 controlled by the three-dimensional displacement adjustment frame C3 to control the position and area of ​​the processing beam irradiated on the sample to be processed C4.

[0063] Reference Figure 3 and Figure 4 ,Compared to the single-wavelength femtosecond laser processing method, when the quartz crystal is processed using the ,above-mentioned method, the temperature rise rate and the temperature rise amount of the ,material C4 to be processed is faster within a single pulse cycle.

[0064] Reference Figure 5 Among them, the upper curve represents the temperature rise curve of the material processed by using a single-wavelength femtosecond laser, and the lower curve represents the temperature rise curve of the material processed by using a multi-wavelength femtosecond laser. Compared with the single-wavelength femtosecond laser processing method, the above method is used to process the quartz crystal. During the entire processing process, the C4 temperature of the material to be processed meets the processing conditions faster, thereby effectively reducing the problems of thermal damage and energy consumption caused by long processing time.

[0065] It should be understood that the core innovation of the present invention lies in: using multiple (two or more) high-power femtosecond lasers that can output different wavelengths, and by adjusting the energy and timing of each laser pulse, the heating process of the processing material is nonlinearly controlled to achieve the goals of reducing energy consumption and improving processing speed and accuracy.

[0066] Example 2:

[0067] In this embodiment, taking the processing of Mini LED wafers as an example, based on the characteristics of Mini LEDs, a femtosecond laser with a central wavelength of 1030nm, an average power of 1W, a repetition rate of 100kHz, and a pulse width of 300fs was selected for processing, while a second femtosecond laser with a central wavelength of 532nm, an average power of 500mW, a repetition rate of 100kHz, and a pulse width of 500fs was selected for processing. The relative delay between the first and second lasers was 200fs. Compared to a single femtosecond laser with the same parameters, the thermal damage to the processed material was reduced, the surface of the Mini LED cutout was smoother, and the processing effect was better.

[0068] Example 3:

[0069] In this example, using the copper sheet as an example, based on the copper sheet's absorption and reflectivity curve, a femtosecond laser with a central wavelength of 532nm, an average power of 30W, a repetition rate of 1kHz, and a pulse width of 800fs was selected for processing, along with a second femtosecond laser with a central wavelength of 355nm, an average power of 30W, a repetition rate of 1kHz, and a pulse width of 300fs. The relative time delay between the first and second lasers was 300fs. Compared to a single femtosecond laser with the same parameters, this laser produces less thermal damage to the material being processed, resulting in a smoother cut surface on the copper sheet, better processing results, and higher efficiency.

[0070] The present embodiment and the specific data are presented only to provide a clearer and more intuitive understanding for those skilled in the art and are merely illustrative, not restrictive, of the present invention. Many changes and modifications may be made within the spirit and scope defined by the claims of the present invention, but all will fall within the scope of protection of the present invention.

Claims

1. A multi-wavelength nonlinear femtosecond laser processing method, characterized in that: The following steps are involved: S1. Using a group of high-power femtosecond lasers to generate multiple high-power femtosecond lasers; the group of high-power femtosecond lasers includes two or more high-power femtosecond lasers that can output different wavelengths, and is used to generate multiple high-power femtosecond lasers including at least two different wavelengths; the high-power femtosecond lasers output by each high-power femtosecond laser have a consistent repetition frequency and adjustable output power; S2, passing each high-power femtosecond laser beam obtained in step S1 through a pair of angle-adjustable thin film reflectors, and then combining the reflected light beams using a beam combiner; S3, allowing the combined light beams obtained in step S2 to enter a beam splitter for splitting each high-power femtosecond laser beam into two paths: a signal light and an idle light; S4, causing the signal light obtained in step S3 to be incident on a photodetector to convert the optical signal into an electrical signal, and then adjusting the thin film mirror pair through an optical path difference and group delay detector to control the optical path difference and group delay of each high-power femtosecond laser, thereby adjusting the idle light in step S3; after the photodetector converts the signal light signals of each channel into an electrical signal, the optical path difference and group delay detector detects the relative delay between each high-power femtosecond laser and calculates the optical path difference, thereby adjusting the tilt angle of each thin film mirror pair to compensate for the optical path difference of each high-power femtosecond laser, thereby achieving time domain adjustment of the idle light; After adjustment, the time for each laser to act on the sample surface is accurately allocated according to the actual application scenario, with an accuracy of femtosecond level; S5. The idle light adjusted in step S4 is passed through a beam focusing module, and the focused laser is vertically irradiated onto the upper surface of the sample to be processed. The nonlinear temperature field is regulated by the different effects of each femtosecond laser on the processed sample, and the processing is finally completed. The temperature field refers to the local temperature field of the sample to be processed where the laser focused by the beam focusing module irradiates the sample to be processed, and the nonlinearity refers to the nonlinear heating method of the sample to be processed during the temperature rise period. The nonlinear temperature field is regulated by changing the output power of each high-power femtosecond laser, controlling the optical path difference and group delay of the high-power femtosecond lasers emitted by different high-power femtosecond lasers through an optical path difference and group delay control module, and controlling the effective area of ​​the emitted laser on the surface of the sample to be processed through a three-dimensional displacement focusing module including a beam focusing module.

2. The multi-wavelength nonlinear femtosecond laser processing method according to claim 1, characterized in that: In step S5, the beam focusing module is fixed on the three-dimensional displacement adjustment frame to form a three-dimensional displacement focusing module, which is used to change the relative position of the beam focus and the surface of the sample to be processed, adjust the spot size on the surface of the sample to be processed, and adapt to the processing requirements of different samples to be processed.

3. A multi-wavelength nonlinear femtosecond laser processing system for implementing the method of claim 1 or 2, characterized in that: It includes a group of high-power femtosecond lasers, an optical path difference and group delay control module and a three-dimensional displacement focusing module; The group of high-power femtosecond lasers includes two or more high-power femtosecond lasers capable of outputting different wavelengths; The optical path difference and group delay control module includes two sets of angle-adjustable thin film reflectors, a set of beam-splitting mirrors, a beam splitter, a photodetector, and an optical path difference and group delay controller; The three-dimensional displacement focusing module includes a beam focusing module and a three-dimensional displacement adjustment frame; A group of high-power femtosecond lasers generates multiple high-power femtosecond lasers with at least two different wavelengths. Each high-power femtosecond laser is reflected by a pair of angle-adjustable thin film reflectors, and then combined by a beam combiner to obtain a combined light beam. The combined light beam is incident on a beam splitter, which splits each high-power femtosecond laser into a signal light and an idle light. The signal light enters the photodetector, which converts the optical signal into an electrical signal. Then, it passes through the optical path difference and group delay detector to achieve precise control of the thin film reflector, control the optical path difference and group delay of each high-power femtosecond laser, and adjust the idle light. The adjusted idle light passes through the beam focusing module, and the focused laser is vertically irradiated onto the upper surface of the sample to be processed, finally completing the processing.

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