High repetition frequency femtosecond laser pulse string two-photon photoetching 3D printing system

Abstract

The invention discloses a high repetition frequency femtosecond laser pulse string two-photon photoetching 3D printing system. The system comprises a laser light source module, a laser transmission system, a sample displacement system, a monitoring system and a programmable terminal. And the laser light source module outputs laser, and the laser is focused into the photoresist through the laser transmission system. The programmable terminal is connected with the laser light source module, the laser transmission system, the sample displacement system and the monitoring system and used for controlling the whole printing process. The light source has the characteristics of high power, high repetition frequency, high stability and the like, can be used for conventional high-resolution small-breadth two-photon photoetching 3D printing, can also be used for long-focal-length large-breadth two-photon photoetching 3D printing, and has important application value in the field of micro-nano manufacturing.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing, and particularly relates to a high-repetition-frequency femtosecond laser pulse train two-photon lithography 3D printing system. Background Art

[0002] As an advanced manufacturing technology, 3D printing technology has been widely used. Among them, two-photon lithography 3D printing technology has important application value in the field of micro-nano manufacturing due to its high resolution. The two-photon lithography 3D printing technology utilizes the two-photon absorption effect to initiate a reaction in the photoresist through high-energy laser pulses, thereby realizing the curing and shaping of the photoresist. This technology can achieve sub-micron spatial resolution and is suitable for manufacturing complex 3D micro-nano structures.

[0003] Traditional two-photon lithography 3D printing systems mostly use free-space lasers (such as titanium-sapphire lasers) as light sources to achieve high-resolution three-dimensional two-photon lithography 3D printing by utilizing the characteristics of femtosecond lasers (an integrated two-photon polymerization processing equipment, the authorized publication number is CN221019124U). Such lasers have defects such as low integration, complex systems, environmental sensitivity, low pulse energy, and insufficient stability, and are not suitable for large-area two-photon lithography 3D printing. In recent years, high-power femtosecond fiber lasers have become a research hotspot due to their compactness and anti-interference ability. High-repetition-frequency femtosecond fiber lasers can effectively solve the light source problem of traditional two-photon lithography 3D printing systems by virtue of the advantages of high repetition frequency, strong anti-interference ability, low phase noise in an ultra-short fiber resonator, and the ability to output in the mode of pulse trains through modulation. By adjusting parameters such as the pulse train frequency, modulation depth, and duty cycle, such lasers can achieve large-area processing that is difficult to achieve with traditional two-photon lithography 3D printing systems. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-repetition-frequency femtosecond laser pulse train two-photon lithography 3D printing system, which can be used for large-area two-photon lithography 3D printing in addition to realizing conventional high-resolution two-photon lithography 3D printing.

[0005] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0006] A high-repetition-frequency femtosecond laser pulse train two-photon lithography 3D printing system includes a laser light source module, a laser transmission system, a sample displacement system, a monitoring system, and a programmable terminal;

[0007] The laser light source module outputs pulsed laser of a set wavelength to the laser transmission system. The laser transmission system focuses the pulsed laser and controls the scanning of the laser spot. The sample displacement system is used to carry the photoresist and move the photoresist; the monitoring system is used to monitor the printing process in real time and determine the position of the laser spot; according to the feedback of the monitoring system, the sample displacement system is adjusted to ensure that the starting position of the laser spot is within the photoresist; the programmable terminal is connected to the laser transmission system, the sample displacement system and the monitoring system and is used to control the printing process:

[0008] The programmable terminal uses software to slice the model to be 3D printed in the horizontal direction in advance to generate the scanning trajectory of each layer of slice;

[0009] During the printing process, the programmable terminal controls the galvanometer in the laser transmission system and the three-dimensional motion platform in the sample displacement system to ensure that the laser spot moves along the predetermined trajectory; after each layer of slice is printed, the three-dimensional motion platform drives the photoresist to move a set distance in the vertical direction, and then the printing of the next layer of slice is carried out until all slices are printed.

[0010] Further, the laser light source module includes a mode-locked seed laser, a high-repetition-rate pulsed fiber amplifier, a dispersion compensator and a frequency doubling module connected in sequence;

[0011] The mode-locked seed laser outputs pulsed laser of a set wavelength. First, the high-repetition-rate pulsed fiber amplifier amplifies the power of the pulsed laser, then the dispersion compensator compresses the pulse width of the pulsed laser, and finally the frequency doubling module doubles the frequency to output high-repetition-rate pulsed laser of a set wavelength.

[0012] Further, the laser transmission system includes a mirror group, a galvanometer and a lens group, which are used to focus the pulsed laser into the photoresist and control the scanning of the laser spot:

[0013] The pulsed laser output by the laser light source module enters the galvanometer through the mirror group of the laser transmission system. The galvanometer controls the scanning pattern of the laser spot, and finally the pulsed laser is focused into the photoresist through the lens group to control the scanning of the laser spot in the photoresist.

[0014] Further, the sample displacement system includes a three-dimensional motion platform, which is used to carry the photoresist and position the photoresist in the X, Y, and Z directions;

[0015] Place the sample stage carrying the photoresist on top of the three-dimensional motion platform. Set the initial coordinate system through the programmable terminal. The X-axis translation stage in the three-dimensional motion platform is used to horizontally move the sample stage in the X direction; the Y-axis translation stage in the three-dimensional motion platform is used to horizontally move the sample stage in the Y direction, and the angle between the Y-axis and the X-axis is 90°; the Z-axis lifting stage in the three-dimensional motion platform is used to vertically move the sample stage in the Z direction, and the angles between the Z-axis and the X-axis and the Y-axis are both 90°. After each layer of slice is printed, the Z-axis lifting stage drives the sample stage to move a set distance in the vertical direction, and then the next layer of slice is printed.

[0016] Further, the monitoring system is optically coupled with the laser transmission system through a dichroic mirror, and includes a beam splitter, an image sensor and an illumination light source, and is used to monitor the printing process in real time:

[0017] The beam splitter is used to deflect the illumination light generated by the illumination light source; the illumination light source is used to provide the illumination light required for monitoring to ensure that the image sensor can clearly capture the images during the printing process; the image sensor is a CCD or CMOS camera, which is optically coupled with the optical path of the laser transmission system through a dichroic mirror, and captures the image information during the printing process in real time.

[0018] Further, the programmable terminal is connected to the laser light source module, the laser transmission system, the sample displacement system and the monitoring system, and is used to comprehensively control the printing process, specifically as follows:

[0019] The programmable terminal controls the mode-locked seed laser in the laser light source module, including starting, stopping, light intensity adjustment and pulse train modulation to ensure the stable operation of the mode-locked seed laser during the printing process; the programmable terminal controls the scanning of the galvanometer and the on / off of the optical path in the laser transmission system to ensure the accurate output of the pulsed laser when needed; the programmable terminal controls the motion trajectory and motion speed of the three-dimensional motion platform in the sample displacement system to ensure high-precision positioning during the printing process; the programmable terminal controls the operation of the image sensor and the imaging software in the monitoring system to monitor the printing process in real time, ensure the printing accuracy and quality, and according to the feedback of the monitoring system, the programmable terminal adjusts the sample displacement system to ensure that the starting position of the laser spot is located within the photoresist.

[0020] Further, in the laser light source module, a mode-locking technology based on an ultra-short fiber resonator is selected for mode locking of the seed laser;

[0021] The mode-locked seed laser uses an ultra-short fiber resonator laser and realizes passive mode locking by using a semiconductor saturable absorber mirror, with a repetition frequency ≥ 1 GHz and an RMS value of power fluctuation ≤ 5%;

[0022] The dispersion compensator is used to compress the pulse width of the pulsed laser to ≤ 300 fs;

[0023] The high-repetition-rate pulsed train fiber amplifier outputs pulsed laser in the mode of pulsed train through modulation, and the frequency of the pulsed train is 1 kHz - 10 MHz.

[0024] Furthermore, the laser transmission system can be switched between a lens group and a long-focal-length field lens. When the lens group is adopted, 3D printing with a spatial resolution ≤ 500 nm can be achieved; when the long-focal-length field lens replaces the lens group, large-format 3D printing with a range ≥ 10×10 mm 2 can be achieved.

[0025] The lens group includes a scanning lens, a tube lens, and an objective lens. The scanning lens is responsible for focusing the pulsed laser output by the galvanometer scanner and making the focus on the required plane; the tube lens is responsible for relay imaging and extending the length of the laser transmission system; the objective lens is responsible for focusing the pulsed laser into the photoresist.

[0026] Furthermore, the stepping resolution of the X-axis translation stage and the Y-axis translation stage in the three-dimensional motion platform is ≤ 1 μm;

[0027] The stepping resolution of the Z-axis lifting stage in the three-dimensional motion platform is ≤ 1 μm.

[0028] Furthermore, the wavelength of the illumination light source of the monitoring system is 600 nm - 700 nm, and the dichroic mirror reflects 780 nm laser and transmits the monitoring band with a wavelength shorter than 780 nm.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] The present invention innovatively proposes a solution of using a high-power GHz fundamental mode locked laser as the laser light source module (101) of the two-photon lithography 3D printing system. By adopting an all-fiber integrated ultrashort fiber resonator mode-locked laser and combining dispersion compensation and nonlinear dynamics regulation, femtosecond pulsed train output with high repetition frequency and high power stability is achieved. It has the following core technical breakthroughs:

[0031] (1) Optimize the structural design scheme of the GHz fundamental mode fiber laser resonator. By adjusting the net dispersion amount in the cavity, wide-spectrum output of the GHz fundamental mode fiber laser is achieved;

[0032] (2) Propose a fiber resonator net dispersion regulation technology based on a dispersion compensation dielectric film for regulating the laser spectral width;

[0033] (3) Through modulation, output in the mode of pulsed train can be achieved, and the pulsed train frequency can be 1 kHz - 10 MHz. By adjusting parameters such as the pulsed train frequency, modulation depth, and duty cycle, lithography under different conditions can be satisfied.

[0034] (4) Through the all-polarization-maintaining fiber structure, the sensitivity of the laser light source module (101) to polarization is reduced, the anti-disturbance characteristics of the laser to environmental temperature, vibration and other factors are significantly improved, and high-stability laser output is achieved;

[0035] (5) By adopting a compact cavity design and cooperating with the all-polarization-maintaining fiber splicing technology, the repetition frequency of the laser light source module (101) of the present invention can reach the GHz level;

[0036] (6) The average power of the laser used in the traditional two-photon lithography 3D printing system is often dozens to hundreds of mW. Due to the small pulse energy and low peak power, limited by the relatively high requirement of the two-photon absorption effect for light intensity, it can only be used for two-photon lithography with a high numerical aperture and high resolution. The working distance is often <1 cm, and the scanning area is often <1×1 mm 2 . Based on the high-power, high-repetition-frequency pulse train 780 nm fiber laser of the present invention, the average power of the output laser reaches the W level, the pulse energy is large, and the peak power is high. It can not only be used for traditional high-resolution two-photon lithography, but also suitable for two-photon lithography with a long focal length and a large scanning area. It can provide a working distance of >10 cm and a scanning area of >10×10 mm 2 , which helps to realize two-photon lithography of a larger volume. Description of the Drawings

[0037] Figure 1 It is a schematic structural diagram of a high-repetition-frequency femtosecond laser pulse train two-photon lithography 3D printing system in an embodiment of the present invention.

[0038] Figure 2 It is a schematic structural diagram of the laser light source module in an embodiment of the present invention.

[0039] Figure 3 It is a schematic structural diagram of the ultra-short fiber resonator mode-locked seed laser used in the laser light source module in an embodiment of the present invention.

[0040] Figure 4 It is a schematic two-photon lithography optical path diagram when the lens group is used in the laser transmission system in an embodiment of the present invention.

[0041] Figure 5 It is a schematic two-photon lithography optical path diagram when the long focal length field lens is used in the laser transmission system in an embodiment of the present invention. Detailed Embodiments

[0042] To enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0043] A high-repetition-rate femtosecond laser pulse train two-photon lithography 3D printing system, as Figure 1 shown, includes a laser light source module 101, a laser transmission system 102, a sample displacement system 103, a monitoring system 104, and a programmable terminal 105;

[0044] In one embodiment, the laser light source module 101 outputs pulsed laser with a wavelength of 780 nm to the laser transmission system 102. The laser transmission system 102 focuses the pulsed laser and controls the scanning of the laser spot. The sample displacement system 103 is used to carry the photoresist and move the photoresist. The monitoring system 104 is used to monitor the printing process in real time to determine the position of the laser spot. According to the feedback of the monitoring system 104, the sample displacement system 103 is adjusted to ensure that the starting position of the laser spot is within the photoresist. The programmable terminal 105 is connected to the laser transmission system 102, the sample displacement system 103, and the monitoring system 104, and is used to control the printing process:

[0045] The programmable terminal 105 uses software to slice the model to be 3D printed in the horizontal direction in advance to generate the scanning trajectory of each layer of slice;

[0046] During the printing process, the programmable terminal 105 controls the galvanometer 404 in the laser transmission system 102 and the three-dimensional motion platform in the sample displacement system 103 to ensure that the laser spot moves along the predetermined trajectory. After each layer of slice is printed, the three-dimensional motion platform drives the photoresist to move a set distance in the vertical direction, and then the printing of the next layer of slice is carried out until all slices are printed.

[0047] As Figure 2 shown, the laser light source module 101 includes a mode-locked seed laser 201, a high-repetition-rate pulse train fiber amplifier 202, a dispersion compensator 203, and a frequency doubling module 204 connected in sequence;

[0048] In one embodiment, the mode-locked seed laser 201 outputs pulsed laser with a wavelength of 1.5 μm. First, the high-repetition-rate pulse train fiber amplifier 202 amplifies the power of the pulsed laser, then the dispersion compensator 203 compresses the pulse width of the pulsed laser, and finally the frequency doubling module 204 doubles the frequency to output high-repetition-rate pulsed laser with a wavelength of 780 nm.

[0049] AsFigure 4 As shown, the laser transmission system 102 includes a mirror group 402, a dichroic mirror 403, a galvanometer 404, and a lens group, which are used to focus pulsed laser into the photoresist and control the scanning of the laser spot:

[0050] The pulsed laser output by the laser light source module 101 enters the galvanometer 404 through the mirror group 402 in the laser transmission system 102. The dichroic mirror 403 is used to deflect the pulsed laser output by the laser light source module 101 and transmit the illumination light generated by the illumination light source 411. The galvanometer 404 is used to control the scanning pattern of the laser spot. Finally, the pulsed laser is focused into the photoresist through the lens group to control the scanning of the laser spot in the photoresist.

[0051] As Figure 4 shown, the sample displacement system 103 includes a three-dimensional motion platform, which is used to carry the photoresist and position the photoresist in the X, Y, and Z directions;

[0052] The sample stage carrying the photoresist is placed on top of the three-dimensional motion platform. The initial coordinates are set through the programmable terminal 105. The X-axis translation stage 407 in the three-dimensional motion platform is used to horizontally move the sample stage in the X direction; the Y-axis translation stage 408 in the three-dimensional motion platform is used to horizontally move the sample stage in the Y direction, and the angle between the Y-axis and the X-axis is 90°; the Z-axis lifting stage 406 in the three-dimensional motion platform is used to vertically move the sample stage in the Z direction, and the angles between the Z-axis and the X-axis and the Y-axis are both 90°. After each layer of slice is printed, the Z-axis lifting stage 406 drives the sample stage to move a set distance in the vertical direction, and then the next layer of slice is printed.

[0053] As Figure 4 shown, the monitoring system 104 is optically coupled to the laser transmission system 102 through the dichroic mirror 403, and includes a beam splitter 409, an image sensor 410, and an illumination light source 411, which are used to monitor the printing process in real time:

[0054] The beam splitter 409 is used to deflect the illumination light generated by the illumination light source 411; the illumination light source 411 is used to provide the illumination light required for monitoring to ensure that the image sensor 410 can clearly capture the images during the printing process; the image sensor 410 is a CCD or CMOS camera, which is optically coupled to the optical path of the laser transmission system 102 through the dichroic mirror 403 to capture the image information during the printing process in real time.

[0055] The programmable terminal 105 is connected to the laser light source module 101, the laser transmission system 102, the sample displacement system 103, and the monitoring system 104, and is used to comprehensively control the printing process, specifically as follows:

[0056] The programmable terminal 105 controls the mode-locked seed laser 201 in the laser light source module 101, including starting, stopping, light intensity adjustment, and pulse train modulation, to ensure the stable operation of the mode-locked seed laser 201 during the printing process; the programmable terminal 105 controls the scanning of the galvanometer 404 and the on / off of the optical path in the laser transmission system 102 to ensure the accurate output of pulsed laser when needed; the programmable terminal 105 controls the motion trajectory and motion speed of the three-dimensional motion platform in the sample displacement system 103 to ensure high-precision positioning during the printing process; the programmable terminal 105 controls the operation of the image sensor 410 and the imaging software in the monitoring system 104 to monitor the printing process in real time, ensure the printing accuracy and quality, and according to the feedback of the monitoring system 104, the programmable terminal 105 adjusts the sample displacement system 103 to ensure that the starting position of the laser spot is on the surface of the photoresist.

[0057] In the laser light source module 101, a mode-locking technology based on an ultrashort fiber resonator is selected for mode locking of the seed laser;

[0058] The mode-locked seed laser 201 uses an ultrashort fiber resonator laser and realizes passive mode locking by using a semiconductor saturable absorber mirror 301, with a repetition frequency ≥ 1 GHz and an RMS value of power fluctuation ≤ 5%;

[0059] In one embodiment, the mode-locked seed laser 201 includes a semiconductor saturable absorber mirror 301, a gain fiber 302, a dielectric film-coated fiber ferrule 303, a laser diode pump source 304, a wavelength division multiplexer 305, and an optical isolator 306; the programmable terminal 105 controls the laser diode pump source 304 to output pump light, the pump light enters the gain fiber 302 through the wavelength division multiplexer 305, and mode locking is achieved in the resonator jointly composed of the semiconductor saturable absorber mirror 301, the gain fiber 302, and the dielectric film-coated fiber ferrule 303, and finally pulsed laser is output, which is filtered by the wavelength division multiplexer 305 and then output, and the optical isolator 306 is used to prevent the return light from affecting the seed mode-locked state.

[0060] The dispersion compensator 203 is used to compress the pulse width of the pulsed laser to ≤ 300 fs;

[0061] The high-repetition-rate pulsed fiber amplifier 202 outputs the pulsed laser in the mode of a pulse train through modulation, and the frequency of the pulse train is 1 kHz - 10 MHz.

[0062] In one embodiment, the step resolution of the X-axis translation stage 407 and the Y-axis translation stage 408 in the three-dimensional motion platform is ≤ 1 μm;

[0063] The step resolution of the Z-axis lifting stage 406 in the three-dimensional motion platform is ≤ 1 μm.

[0064] In one embodiment, the wavelength of the illumination light source 411 of the monitoring system 104 is 600 nm to 700 nm. The dichroic mirror 403 reflects the 780 nm laser and transmits the monitoring band with a wavelength shorter than 780 nm.

[0065] The laser transmission system 102 can be switched between the lens group and the long focal length field lens 405. When the lens group is used, 3D printing with a spatial resolution ≤ 500 nm can be achieved; when the long focal length field lens 405 replaces the lens group, large-format 3D printing with a range ≥ 10 × 10 mm 2 can be achieved.

[0066] The lens group includes a scanning lens 501, a lens barrel lens 502, and an objective lens 503. The scanning lens 501 is responsible for focusing the pulsed laser output by the galvanometer 404 and making the focus on the required plane; the lens barrel lens 502 is responsible for relay imaging and extending the length of the laser transmission system 102; the objective lens 503 is responsible for focusing the pulsed laser into the photoresist.

[0067] In one embodiment, a field lens 405 (SL-780-150-210G) with a focal length of f = 160 mm is used as the core optical device to achieve a processing area of 110 × 110 mm 2 processing area.

[0068] The laser source module 101 outputs a laser with a repetition frequency of 1 GHz and a pulse width of 300 fs. The mode-locked seed laser 201 is turned on and waits for it to self-start. Subsequently, the high-repetition-rate pulsed fiber amplifier 202 is turned on step by step. The pulse train repetition frequency is set to 1 kHz, and the output power is 1 W. After being compressed by the dispersion compensator 203, the laser enters the frequency doubling module 204, and finally, pulsed laser with a wavelength of 780 nm and a pulse width of 300 fs is obtained. This pulsed laser is incident on the galvanometer 404 through the mirror group 402 and the dichroic mirror 403. The galvanometer 404 scans at a rate of 50 mm / s and is then focused on the upper surface of the sample stage by the field lens 405 with a focal length of f = 160 mm. The focused laser spot can scan within a large area of 110 × 110 mm 2 The model to be 3D printed is imported into the computer, and the software performs layer-by-layer segmentation to generate the scanning trajectory of each layer of the model. The computer controls the galvanometer 404 and the three-dimensional motion platform according to the program, so that the laser spot performs layer-by-layer printing in a "bow"-shaped scanning mode according to the predetermined trajectory. After each layer of printing is completed, the Z-axis lifting table 406 drives the sample stage to move downward by a certain position. The printing process is monitored in real time by connecting the computer to the monitoring system 104.

[0069] In one embodiment, a high numerical aperture (NA = 1.4) oil immersion objective lens 503 is used as the core optical device, and a 200 nm line width processing is achieved by combining the adaptive power modulation technology. The specific technical solution is as follows:

[0070] In this embodiment, the laser light source module 101 outputs a repetition rate of 5 GHz and a pulse width of 100 fs. The mode-locked seed laser 201 is turned on and waits for it to self-start. Subsequently, the high-repetition-rate pulsed fiber amplifier 202 is turned on step by step. The repetition rate of the pulse train is set to 1 MHz, and the output power is 25 mW. After being compressed by the dispersion compensator 203, the laser enters the frequency doubling module 204, and finally, pulsed laser light with a wavelength of 780 nm and a pulse width of 100 fs is obtained. This pulsed laser light is incident on the galvanometer 404 through the mirror group 402. The galvanometer scans at a rate of 10 mm / s. After the light beam is collimated by the scanning lens 501, it is then transmitted through the tube lens 502 to the high numerical aperture objective lens 503. The high numerical aperture objective lens 503 focuses the light beam into the photoresist located at the bottom of the glass slide. The glass slide-photoresist interface is positioned by the image sensor 410, and the computer sends instructions to the sample displacement system 103 for axial positioning with an accuracy of 0.1 μm. The model obtained by 3D printing is imported into the computer. The software performs layer-by-layer segmentation of the model to generate the scanning trajectory of each layer of the model. The computer controls the galvanometer 404 and the three-dimensional motion platform according to the program, and the laser spot scans layer by layer in a "bow" - shaped scanning mode along the predetermined trajectory. After each layer is printed, the Z-axis lifting stage 406 drives the sample stage to move upward by a certain position. The printing process is monitored in real time through the computer-connected monitoring system 104.

Claims

1. A two-photon lithography 3D printing system for high-repetition-rate femtosecond laser pulse trains, characterized in that, It includes a laser light source module (101), a laser transmission system (102), a sample displacement system (103), a monitoring system (104) and a programmable terminal (105); The laser light source module (101) outputs pulsed laser of a set wavelength to the laser transmission system (102). The laser transmission system (102) focuses the pulsed laser and controls the scanning of the laser spot. The sample displacement system (103) is used to carry the photoresist and move the photoresist. The monitoring system (104) is used to monitor the printing process in real time and determine the position of the laser spot. According to the feedback of the monitoring system (104), the sample displacement system (103) is adjusted to ensure that the starting position of the laser spot is within the photoresist. The programmable terminal (105) is connected to the laser transmission system (102), the sample displacement system (103) and the monitoring system (104) and is used to control the printing process: The programmable terminal (105) slices the model to be 3D printed in the horizontal direction in advance to generate the scanning trajectory of each layer of slice; During the printing process, the programmable terminal (105) controls the galvanometer (404) in the laser transmission system (102) and the three-dimensional motion platform in the sample displacement system (103) to ensure that the laser spot moves along the predetermined trajectory. After each layer of slice is printed, the three-dimensional motion platform drives the photoresist to move a set distance in the vertical direction, and then the printing of the next layer of slice is carried out until all slices are printed.

2. The two-photon lithography 3D printing system for high-repetition-rate femtosecond laser pulse trains according to claim 1, wherein The laser light source module (101) includes a mode-locked seed laser (201), a high-repetition-rate pulsed train fiber amplifier (202), a dispersion compensator (203) and a frequency doubling module (204) connected in sequence; The mode-locked seed laser (201) outputs pulsed laser of a set wavelength. First, the high-repetition-rate pulsed train fiber amplifier (202) amplifies the power of the pulsed laser, then the dispersion compensator (203) compresses the pulse width of the pulsed laser, and finally the frequency doubling module (204) doubles the frequency to output high-repetition-rate pulsed laser of a set wavelength.

3. A two-photon lithography 3D printing system for high-repetition-rate femtosecond laser pulse trains according to claim 1, characterized in that, The laser transmission system (102) includes a mirror group (402), a galvanometer (404) and a lens group, and is used to focus the pulsed laser into the photoresist and control the scanning of the laser spot: The pulsed laser output by the laser light source module (101) enters the galvanometer (404) through the mirror group (402) of the laser transmission system (102). The galvanometer (404) controls the scanning pattern of the laser spot, and finally the pulsed laser is focused into the photoresist through the lens group to control the scanning of the laser spot in the photoresist.

4. A two - photon lithography 3D printing system for high - repetition - rate femtosecond laser pulse trains according to claim 1, wherein, The sample displacement system (103) includes a three-dimensional motion platform and is used to carry the photoresist and position the photoresist in the X, Y, and Z directions; Place the sample stage carrying the photoresist on top of the three-dimensional motion platform. Set the initial coordinates through the programmable terminal (105). The X-axis translation stage (407) in the three-dimensional motion platform is used to horizontally move the sample stage in the X direction; the Y-axis translation stage (408) in the three-dimensional motion platform is used to horizontally move the sample stage in the Y direction, and the angle between the Y-axis and the X-axis is 90°; the Z-axis lifting stage (406) in the three-dimensional motion platform is used to vertically move the sample stage in the Z direction, and the angles between the Z-axis and the X-axis and the Y-axis are both 90°. After each layer of slice is printed, the Z-axis lifting stage (406) drives the sample stage to move a set distance in the vertical direction, and then the next layer of slice is printed.

5. A two-photon lithography 3D printing system for high-repetition-rate femtosecond laser pulse trains according to claim 1, characterized in that, The monitoring system (104) is optically coupled to the laser transmission system (102) through a dichroic mirror (403), and includes a beam splitter (409), an image sensor (410) and an illumination light source (411), and is used to monitor the printing process in real time: The beam splitter (409) is used to deflect the illumination light generated by the illumination light source (411); the illumination light source (411) is used to provide the illumination light required for monitoring to ensure that the image sensor (410) can clearly capture the images during the printing process; the image sensor (410) is a CCD or CMOS camera, which is optically coupled to the laser transmission system (102) through a dichroic mirror (403) to capture the image information during the printing process in real time.

6. A two-photon lithography 3D printing system for high-repetition-rate femtosecond laser pulse trains according to any one of claims 1 to 5, characterized in that, The programmable terminal (105) is connected to the laser light source module (101), the laser transmission system (102), the sample displacement system (103) and the monitoring system (104), and is used to comprehensively control the printing process as follows: The programmable terminal (105) controls the mode-locked seed laser (201) in the laser light source module (101), including starting, stopping, light intensity adjustment and pulse train modulation; the programmable terminal (105) controls the scanning of the galvanometer (404) and the on / off of the optical path in the laser transmission system (102); the programmable terminal (105) controls the motion trajectory and motion speed of the three-dimensional motion platform in the sample displacement system (103); the programmable terminal (105) controls the operation of the image sensor (410) in the monitoring system (104) to monitor the printing process in real time; according to the feedback of the monitoring system (104), the programmable terminal (105) adjusts the sample displacement system (103) to ensure that the starting position of the laser spot is within the photoresist.

7. A two-photon lithography 3D printing system for high-repetition-rate femtosecond laser pulse trains according to claim 2, wherein, The mode-locked seed laser (201) uses an ultra-short fiber resonator laser and realizes passive mode locking by using a semiconductor saturable absorber mirror (301), with a repetition frequency ≥1 GHz and an RMS value of power fluctuation ≤5%; The dispersion compensator (203) is used to compress the pulse width of the pulsed laser to ≤300 fs; The high-repetition-frequency pulsed fiber amplifier (202) outputs pulsed laser in the form of a pulse train through modulation, and the frequency of the pulse train is 1 kHz - 10 MHz.

8. A two-photon lithography 3D printing system for high-repetition-rate femtosecond laser pulse trains according to claim 3, characterized in that, The laser transmission system (102) switches between a lens group and a long focal length field lens (405). When using the lens group, 3D printing with a spatial resolution ≤ 500 nm is achieved; when using the long focal length field lens (405) to replace the lens group, large-format 3D printing with a range ≥ 10 × 10 mm 2 is achieved. The lens group includes a scanning lens (501), a barrel lens (502), and an objective lens (503). The scanning lens (501) is responsible for focusing the pulsed laser output by the galvanometer (404) and making the focus on the required plane; the barrel lens (502) is responsible for relay imaging and extending the length of the laser transmission system (102); the objective lens (503) is responsible for focusing the pulsed laser within the photoresist.

9. A two-photon lithography 3D printing system for high-repetition-rate femtosecond laser pulse trains according to claim 4, wherein, The step resolution of the X-axis translation stage (407) and the Y-axis translation stage (408) in the three-dimensional motion platform is ≤1 μm; The step resolution of the Z-axis lifting stage (406) in the three-dimensional motion platform is ≤1 μm.

10. A two-photon lithography 3D printing system for high-repetition-rate femtosecond laser pulse trains according to claim 5, characterized in that, The wavelength of the illumination light source (411) of the monitoring system (104) is 600 nm to 700 nm. The dichroic mirror (403) reflects the 780-nm laser and transmits the monitoring band with a wavelength shorter than 780 nm.

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