Multi-wavelength nonlinear femtosecond laser processing method and system

Abstract

A multi-wavelength nonlinear femtosecond laser processing method, comprising: using a plurality of high-power femtosecond lasers (A) to emit high-power femtosecond laser light of different wavelengths; accurately controlling the optical path difference and group delay of the laser light emitted by the lasers by means of an optical path difference and group delay control module (B); enabling the multi-wavelength femtosecond laser light to be incident on a three-dimensional displacement focusing module (C); and finally, enabling the laser light to be vertically incident on the upper surface of a sample to be processed (C4) so as to complete femtosecond laser processing. In the method, by precisely modulating the relative positions of laser pulses of different wavelengths in a time domain, dynamic nonlinear precise regulation and control for a temperature field of a sample processing area are achieved, improving the efficiency, quality and depth of precision processing, and expanding the application range of femtosecond laser precision processing. The present invention further relates to a multi-wavelength nonlinear femtosecond laser processing system.

Description

A multi-wavelength nonlinear femtosecond laser processing method and system TECHNICAL FIELD

[0001] The present application relates to the field of laser application, and particularly relates to a multi-wavelength nonlinear femtosecond laser processing method and system. BACKGROUND

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

[0003] Compared with the continuous light laser processing, the femtosecond laser processing has higher peak energy and more ordered energy output. This also means that the use of femtosecond laser for material processing can process a wider variety of materials, has greater processing depth, smaller heat damage outside the material processing area, higher processing quality, and further improved processing speed and efficiency.

[0004] At present, the femtosecond laser processing field mainly uses a single-wavelength solid laser source. Compared with the fiber femtosecond laser, the solid femtosecond laser has a series of disadvantages such as large volume, easy damage, high maintenance difficulty and high cost. On the other hand, using a single-wavelength laser for processing with the existing technical means also has many limitations. For example: poor adaptability to different materials, only materials with high absorption rate at this wavelength can be selected for processing; the material heating mode is linear heating, the heating speed is slow, and the heat is easily conducted to the surrounding of the processing area, resulting in poor processing quality; the local transient temperature field of the processing area cannot be actively and accurately modulated; and so on.

[0005] The existing multi- (dual-) wavelength laser processing method is realized by a single laser emitting a fundamental light and frequency doubling the fundamental light. This scheme improves the defects of the above-mentioned single-wavelength laser processing method to some extent, but does not completely break through the constraints of the above-mentioned problems.

[0006] In the prior art, the multi-wavelength laser processing device mentioned in the multi-wavelength laser processing device includes a multi-wavelength laser emitting laser beams of different wavelengths, a laser processing system, and a laser beam combining device; the laser processing system includes a galvanometer assembly, and the galvanometer assembly 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 reflecting mirror, a second reflecting mirror, and a first multi-color beam combining mirror; the first dispersion compensation assembly includes a first right-angle mirror and a first prism through which the laser beams of the first wavelength pass; the second dispersion compensation assembly includes a second right-angle mirror and a second prism through which the laser beams of the second wavelength pass; the first reflecting mirror reflects the laser beams of the first wavelength after dispersion compensation and combines the laser beams of the second wavelength after dispersion compensation at the first multi-color beam combining mirror, and the combined laser beams are reflected by the second reflecting mirror into the scanning galvanometer and then focused by the focusing mirror to process a workpiece. Since there is no optical path difference and group delay detector, the relative time delay of the laser beams of different wavelengths cannot be changed, and the material cannot be processed with high precision. The three wavelengths (red light, green light, and purple light) used are fixed and cannot be changed, and it is difficult to adapt to the absorption characteristics of different materials (CN112091416A). SUMMARY

[0007] Therefore, the multi-wavelength nonlinear femtosecond laser processing method provided by the application can effectively overcome the above problems. A plurality of femtosecond fiber lasers with different output wavelengths are used as processing light sources, and the material type, material processing precision, speed, depth, and quality are improved by time domain regulation of each laser.

[0008] The object of the application is achieved at least by one of the following technical solutions.

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

[0010] S1, using a group of high-power femtosecond lasers to generate a plurality of high-power femtosecond lasers of at least two different wavelengths;

[0011] S2, making each high-power femtosecond laser obtained in step S1 pass through a pair of angle-adjustable film mirrors, and then using a beam combining mirror to combine each reflected light;

[0012] S3, making the light beam obtained after the beam combining in step S2 incident on a beam splitter for dividing the high-power femtosecond lasers into signal light and idle light;

[0013] S4, making the signal light obtained in step S3 incident on a photoelectric detector to convert the optical signal into an electrical signal, and then passing through an optical path difference and group delay detector to further regulate the film mirror pair and control the optical path difference and group time delay of each high-power femtosecond laser, and adjust the idle light in step S3;

[0014] S5, the idle light adjusted in step S4 passes through a beam focusing module, the focused laser is vertically irradiated to the upper surface of the sample to be processed, the different effects of the various femtosecond lasers on the sample to be processed are used to adjust the nonlinear temperature field, and finally the processing is completed.

[0015] Further, in step S1, the group of high-power femtosecond lasers includes two or more high-power femtosecond lasers capable of outputting different wavelengths, for generating multiple high-power femtosecond lasers with at least two different wavelengths.

[0016] Further, the high-power femtosecond lasers output by each high-power femtosecond laser have consistent repetition frequencies, and the output power is adjustable.

[0017] Further, in step S4, after the photodetector converts the various signal light signals into electrical signals, the optical path difference and group delay detector detects the relative time delay between the various high-power femtosecond lasers and calculates the optical path difference, and then adjusts the tilt angle of each thin film mirror pair to compensate for the optical path difference of the various high-power femtosecond lasers, thereby adjusting the time domain of the idle light.

[0018] After adjustment, according to the actual application scene, the time of each laser acting on the sample surface is accurately allocated, and the accuracy reaches the fs level.

[0019] Further, 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 sample surface to be processed, adjust the spot size of the sample surface to be processed, and adapt to the processing requirements of different samples to be processed.

[0020] Further, in step S5, the temperature field refers to the local temperature field of the laser irradiated on the sample to be processed after being focused by the beam focusing module, and the nonlinearity refers to the non-linear heating mode of the sample to be processed during temperature rise.

[0021] Further, in step S5, the way to adjust the nonlinear temperature field includes changing the output power of each high-power femtosecond laser.

[0022] Further, in step S5, the way to adjust the nonlinear temperature field includes controlling the optical path difference and group delay of the high-power femtosecond lasers emitted by different high-power femtosecond lasers through the optical path difference and group delay control module.

[0023] Further, in step S5, the way to adjust the nonlinear temperature field includes controlling the action area of the outgoing laser on the sample surface to be processed through the three-dimensional displacement focusing module.

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

[0025] The group of high-power femtosecond laser, including two or more high-power femtosecond laser that can output different wavelengths;

[0026] The optical path difference and group delay control module includes two groups of angle-adjustable film mirrors, a beam combiner, 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] Wherein, a group of high-power femtosecond laser generates multiple high-power femtosecond lasers including at least two different wavelengths;Each high-power femtosecond laser is reflected by two groups of angle-adjustable film mirrors, and then the reflected light is combined by the beam combiner to obtain the combined light beam;

[0029] The signal light is incident on the photodetector, and the optical signal is converted into an electrical signal, and then the optical path difference and group delay detector is used to accurately control the film mirror, 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 to the upper surface of the sample to be processed, and finally the processing is completed.

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

[0032] The present application uses multiple high-power femtosecond lasers that output different wavelengths of laser, and uses a series of means to regulate the temperature field of the sample processing area, improves the precision machining efficiency, quality and processing depth, and expands the application range of femtosecond laser precision machining. BRIEF DESCRIPTION OF DRAWINGS

[0033] Fig. 1 is a structural schematic diagram of a multi-wavelength nonlinear femtosecond laser processing system according to an embodiment of the present application;

[0034] Fig. 2 is a timing arrangement diagram of different wavelength pulses in a single pulse period according to an embodiment of the present application;

[0035] Fig. 3 is a temperature rise curve diagram of using single-wavelength femtosecond laser to process materials in a single pulse period according to an embodiment of the present application;

[0036] Fig. 4 is a schematic diagram of a temperature rising curve of a material processed by using a multi-wavelength femtosecond laser in a single pulse period according to an embodiment of the present application;

[0037] Fig. 5 is a schematic diagram of a temperature rising curve of a material processed by using a single-wavelength femtosecond laser and a temperature rising curve of a material processed by using a multi-wavelength femtosecond laser in a whole processing process according to an embodiment of the present application. Embodiments of the present application

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

[0039] Embodiments

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

[0041] S1, using a group of high-power femtosecond lasers to generate a plurality of high-power femtosecond lasers of at least two different wavelengths;

[0042] The group of high-power femtosecond lasers includes two or more high-power femtosecond lasers capable of outputting different wavelengths, for generating a plurality of high-power femtosecond lasers of at least two different wavelengths.

[0043] The high-power femtosecond lasers output by each high-power femtosecond laser have consistent repetition frequencies and adjustable output powers.

[0044] S2, making each of the plurality of high-power femtosecond lasers obtained in step S1 pass through a pair of angle-adjustable thin film mirrors, and then using a beam combiner to combine the reflected lights;

[0045] S3, making the light beam obtained after the combination in step S2 incident on a beam splitter, for splitting the plurality of high-power femtosecond lasers into signal light and idle light;

[0046] S4, making the signal light obtained in step S3 incident on a photodetector to convert the optical signal into an electrical signal, and then passing through an optical path difference and group delay detector to further control the pair of thin film mirrors and control the optical path difference and group delay of each of the plurality of high-power femtosecond lasers, and adjust the idle light in step S3;

[0047] After the photodetector converts the plurality of signal lights into electrical signals, the optical path difference and group delay detector detects the relative time delay between the plurality of high-power femtosecond lasers and calculates the optical path difference, and then adjusts the tilt angle of each pair of thin film mirrors to compensate for the optical path difference of the plurality of high-power femtosecond lasers, thereby achieving time-domain adjustment of the idle light;

[0048] After adjustment, according to the actual application scene, the time of each laser acting on the sample surface is accurately allocated, and the accuracy reaches the fs level.

[0049] S5, the idle light adjusted in step S4 passes through the beam focusing module, the focused laser is vertically irradiated to the upper surface of the sample to be processed, the different effects of the various femtosecond lasers on the processed sample are realized, the nonlinear temperature field is regulated, and the processing is finally completed.

[0050] The beam focusing module is fixed on the three-dimensional displacement adjusting frame to form a three-dimensional displacement focusing module, which is used to change the relative position of the beam focus point and the sample surface to be processed, adjust the spot size of the sample surface 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 laser irradiated on the sample to be processed after being focused by the beam focusing module, and the nonlinearity refers to the non-linear heating mode of the sample to be processed during temperature rise.

[0052] The method for regulating the nonlinear temperature field includes 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 the high-power femtosecond laser emitted by different high-power femtosecond lasers through the optical path difference and group delay control module.

[0054] The method for regulating the nonlinear temperature field includes controlling the action area of the outgoing laser on the sample surface to be processed through the 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 is shown in FIG. 1, which 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 A1, A2, …, An that can output different wavelengths. n n is the number of high-power femtosecond lasers, n≥2;

[0057] The optical path difference and group delay control module includes two groups of angle-adjustable film mirrors, a beam combining mirror, a beam splitter B4, a photodetector B5, and an optical path difference and group delay controller B6. 11 B 12 B 1n The first group of n angle-adjustable film mirrors is electrically controlled, n≥2. 21 B 22 B2n A second set of n angle-controlled thin film mirrors; 31 A second set of n angle-controlled thin film mirrors; 32 A second set of n angle-controlled thin film mirrors; 3n A second set of n angle-controlled thin film mirrors;

[0058] The three-dimensional displacement focusing module C comprises a plane mirror C1, a light beam focusing module C2, a three-dimensional displacement adjusting frame C3 and a sample to be processed C4.

[0059] According to the absorption spectrum, melting point and other characteristics of the quartz crystal, 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 second high-power femtosecond laser A2, respectively; wherein the output power of the first high-power femtosecond laser A1 is 1000W, the repetition frequency is 1GHz, and the pulse width is 300fs; the output power of the second high-power femtosecond laser A2 is 200W, the repetition frequency is 1GHz, and the pulse width is 200fs.

[0060] The first high-power femtosecond laser A1 enters the optical path difference and group delay control module B, and sequentially passes through the angle-controlled first thin film mirror B 11 , B 21 , and the first beam combiner B 31 which has high transmittance to 1.0 μm laser and high reflectivity to 2.0 μm laser; 12 The laser output by the second high-power femtosecond laser A2 respectively passes through the angle-controlled second thin film mirror B 22 , B 32 , the second beam combiner B 31 which has high reflectivity to 2.0 μm laser, and the first beam combiner B 11 which has high transmittance to 1.0 μm laser and high reflectivity to 2.0 μm laser; 21 After beam combining, the obtained light beam after beam combining is incident on the beam splitter B4.

[0061] After the obtained light beam after beam combining is split by the beam splitter B4, one of the lasers is incident on the photodetector B5 as signal light, and then transmitted to the optical path difference and group delay controller B6. Through the output of the electrical control signal of the optical path difference and group delay controller B6, the angle-controlled first thin film mirror B 21 , B 12 , and the second thin film mirror B 22The wavefront of the 2.0-micron femtosecond laser is advanced 100 fs of the 1.0-micron femtosecond laser, and the time sequence arrangement of the two laser pulses is shown in FIG. 2, wherein the solid line represents the single pulse energy distribution of the femtosecond fiber laser with an output wavelength of 2.0 microns and a repetition frequency of 1 GHz, and the dashed line represents the single pulse energy distribution of the femtosecond fiber laser with an output wavelength of 1.0 microns and a repetition frequency 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 an idle light, is reflected by the plane mirror C1, and is incident on the beam focusing module C2 controlled by the three-dimensional displacement adjusting frame C3 to control the position and area of the processing beam irradiated on the sample C4 to be processed.

[0063] Referring to FIGS. 3 and 4, compared with the single-wavelength femtosecond laser processing method, the quartz crystal is processed by using the above method, and in a single pulse period, the temperature rising speed of the material C4 to be processed is faster, and the temperature rising amount is higher.

[0064] Referring to FIG. 5, the upper curve represents the temperature rising curve of the material processed by using the single-wavelength femtosecond laser, and the lower curve represents the temperature rising curve of the material processed by using the multi-wavelength femtosecond laser; compared with the single-wavelength femtosecond laser processing method, the quartz crystal is processed by using the above method, and in the whole processing process, the temperature of the material C4 to be processed satisfies the processing condition faster, thereby effectively reducing the problems of heat damage, energy consumption and the like caused by a long processing time.

[0065] It should be understood that the core innovation of the present application is that a plurality of (two or more) high-power femtosecond lasers capable of outputting different wavelengths are used, the energy and time sequence of each laser pulse are adjusted, the temperature rising process of the material to be processed is nonlinearly regulated, and the purposes of reducing energy consumption, improving processing speed and precision and the like are achieved.

[0066] Embodiment 2

[0067] In this embodiment, taking the processing of the Mini LED wafer as an example, according to the characteristics of the Mini LED, one route of femtosecond laser with a center wavelength of 1030 nm, an average power of 1 W, a repetition frequency of 100 kHz and a pulse width of 300 fs is selected, and another route of femtosecond laser with a center wavelength of 532 nm, an average power of 500 mW, a repetition frequency of 100 kHz and a pulse width of 500 fs is selected for processing. The relative time delay of the first laser and the second laser is 200 fs. Compared with the single-route femtosecond laser with the same parameters, the heat damage of the material to be processed is smaller, the surface of the Mini LED incision is smoother, and the processing effect is better.

[0068] Embodiment 3

[0069] In this embodiment, taking a copper sheet as an example, according to the absorption reflectivity curve of the copper sheet, a femtosecond laser with a center wavelength of 532 nm, an average power of 30 W, a repetition frequency of 1 kHz and a pulse width of 800 fs is selected for processing, and another femtosecond laser with a center wavelength of 355 nm, an average power of 30 W, a repetition frequency of 1 kHz and a pulse width of 300 fs is selected for processing. The relative time delay of the first laser and the second laser is 300 fs. Compared with a single-path femtosecond laser with the same parameters, the heat damage of the material to be processed is smaller, the surface of the copper sheet cut is smoother, the processing effect is better, and the processing efficiency is higher.

[0070] The presentation of the embodiment and the specific data is only to provide a clearer and more intuitive understanding for the professional technical personnel, and is only illustrative but not limiting for the present application. Many changes and modifications can be made within the spirit and scope defined by the claims of the present application, and all will fall within the protection scope of the present application.

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 having at least two different wavelengths; 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, 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; 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.

2. The multi-wavelength nonlinear femtosecond laser processing method according to claim 1, characterized in that: In step S1 , the group of high-power femtosecond lasers includes two or more high-power femtosecond lasers capable of outputting different wavelengths, and is configured to generate multiple high-power femtosecond lasers having at least two different wavelengths.

3. The multi-wavelength nonlinear femtosecond laser processing method according to claim 2, characterized in that: The high-power femtosecond laser repetition frequency output by each high-power femtosecond laser is consistent, and the output power is adjustable.

4. The multi-wavelength nonlinear femtosecond laser processing method according to claim 1, characterized in that: In step S4, after the photodetector converts the signal light 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 achieve time domain regulation 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 the fs level.

5. 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.

6. The multi-wavelength nonlinear femtosecond laser processing method according to claim 1, characterized in that: In step S5, the temperature field refers to the local temperature field of the sample to be processed when the laser beam focused by the beam focusing module is 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.

7. The multi-wavelength nonlinear femtosecond laser processing method according to claim 1, characterized in that: In step S5 , the nonlinear temperature field is controlled by changing the output power of each high-power femtosecond laser.

8. The multi-wavelength nonlinear femtosecond laser processing method according to claim 1, characterized in that: 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.

9. The multi-wavelength nonlinear femtosecond laser processing method according to claim 1, characterized in that: In step S5, the nonlinear temperature field is regulated by controlling the effective area of ​​the emitted laser on the surface of the sample to be processed by a three-dimensional displacement focusing module.

10. A multi-wavelength nonlinear femtosecond laser processing system, 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 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. 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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