A wavelength-tunable high-repetition-rate femtosecond laser based on supercontinuum effect and a two-photon lithography system

Abstract

The application discloses a wavelength-tunable high-repetition-rate femtosecond laser based on supercontinuum effect and a two-photon photoetching system. The femtosecond laser comprises a high-repetition-rate femtosecond laser seed source, a pulse modulator, a pulse amplifier, a frequency doubling module and a tunable filter module; the high-repetition-rate femtosecond laser seed source, the pulse modulator, the pulse amplifier, the frequency doubling module and the tunable filter module are sequentially arranged, the high-repetition-rate femtosecond laser seed source is used for outputting pulse laser, the pulse modulator is used for adjusting the peak power of the pulse laser, the pulse amplifier is used for amplifying the power of the pulse laser, the frequency doubling module is used for frequency doubling the pulse laser and filtering out fundamental frequency light, and the tunable filter module is used for exciting supercontinuum and realizing continuous adjustment of the output wavelength by adjusting the transmission wavelength range. The wavelength filtered by the filter can be adjusted, and the target wave required can be easily and quickly selected.

Description

Technical Field

[0001] This invention belongs to the field of laser applications, specifically relating to a wavelength-tunable high-repetition-rate femtosecond laser and a two-photon lithography system based on the supercontinuum effect. Background Technology

[0002] Two-photon lithography utilizes the two-photon absorption effect of laser light in materials, causing the light-induced reaction to occur only within the focal point, thus achieving selective curing. This additive manufacturing technology offers high resolution, with feature sizes even smaller than 100 nm, and can be used for additive manufacturing of complex three-dimensional micro / nano structures such as overhangs, hollow structures, and interlocking structures.

[0003] Traditional two-photon lithography often relies on a single, fixed-wavelength laser source, such as 780 nm or 532 nm (see "A Method for Rapid Fabrication of Multi-Scale Three-Dimensional Microstructures, Publication No. CN111913364A"). However, different materials exhibit varying optical properties such as absorptivity and transmittance, and different processes have different requirements for laser wavelength. Therefore, single-wavelength laser sources suffer from poor material and process adaptability, which also restricts the development of new materials compatible with two-photon lithography technology. Improvements in printing accuracy, processing efficiency, and expanded material and process compatibility all place higher demands on the wavelength tunability of laser sources. Summary of the Invention

[0004] The purpose of this invention is to provide a wavelength-tunable high-repetition-rate femtosecond laser and a two-photon lithography system based on the supercontinuum effect, which can achieve adaptive two-photon lithography for different materials by tuning the wavelength. This invention utilizes the highly nonlinear characteristics of photonic crystal fibers, which can convert the energy of high peak power laser pulses into extremely broad spectral broadening over an extremely short distance, exciting a supercontinuum. By using a tunable filter to perform narrowband filtering on the supercontinuum, pulsed laser light of the desired wavelength can be output, achieving continuous wavelength tuning. The principle of obtaining the supercontinuum in this invention is as follows: The soliton order is positively correlated with the peak power of the pulsed laser. Therefore, higher peak power is beneficial for increasing the soliton order, which intensifies soliton splitting and generates more ground-state solitons. These ground-state solitons continuously transfer their energy to longer wavelengths through the soliton self-frequency shift effect, thus extending the spectral composition to longer wavelengths. Simultaneously, increasing the peak power of the incident laser increases the peak power of the fundamental-order optical solitons formed in the fiber, and according to the soliton characteristics, their pulse width will correspondingly narrow. The combined effect of increased peak power and narrowed pulse width significantly enhances the nonlinear phase shift generated by the soliton, disrupting the original phase-matching equilibrium. In the normal dispersion region of the dispersive wave, the propagation constant increases with frequency. To rebuild the phase-matching equilibrium, the new phase-matching point shifts to higher frequencies, coupling energy to shorter wavelengths through the dispersive wave effect, thus extending the spectrum to shorter wavelengths. Under the combined effect of the soliton self-frequency shift and the dispersive wave effect, the spectrum is significantly broadened to both sides, resulting in a supercontinuum.

[0005] By modulating the laser pulses, the peak power of the input laser can be increased and the width of the supercontinuum extended without changing the average power of the laser input to the photonic crystal fiber. Furthermore, by co-modulating the laser pulse sequence of the input photonic crystal fiber and adjusting the average power of the input laser, the output laser power of the photonic crystal fiber can be adjusted without changing the spectral width of the excited laser.

[0006] The present invention is achieved by at least one of the following technical solutions.

[0007] A wavelength-tunable high-repetition-rate femtosecond laser based on the supercontinuum effect includes a high-repetition-rate femtosecond laser seed source, a pulse modulator, a pulse amplifier, a frequency doubling module, and a tunable filter module. The high-repetition-rate femtosecond laser seed source, pulse modulator, pulse amplifier, frequency doubling module, and tunable filter module are arranged sequentially. The high-repetition-rate femtosecond laser seed source is used to output pulsed laser, the pulse modulator is used to adjust the peak power of the pulsed laser, the pulse amplifier is used to amplify the power of the pulsed laser, the frequency doubling module is used to double the frequency of the pulsed laser and filter out the fundamental frequency light, and the tunable filter module is used to excite the supercontinuum and achieve continuous adjustment of the output wavelength by adjusting the transmission band.

[0008] The high-repetition-rate femtosecond laser seed source outputs pulsed laser of a specific wavelength. First, the duty cycle of the pulse modulator is set to adjust the peak power of the pulsed laser. Then, the power of the pulsed laser is amplified by the pulse amplifier. Subsequently, the laser is frequency-doubled by the frequency doubling module and the fundamental frequency light is filtered out. Finally, the supercontinuum is excited by the photonic crystal fiber in the tunable filter module. The transmission band of the tunable filter in the tunable filter module is adjusted to filter out a continuously tunable laser with a wavelength in the range of 500-800 nm, and the frequency-doubled light that has not undergone frequency conversion is filtered out.

[0009] A two-photon lithography system includes the femtosecond laser, a spatial optical path, a processing platform, and a control terminal; The femtosecond laser outputs a femtosecond laser of a specific wavelength, which is transmitted to the processing platform via a spatial optical path to process the photoresist placed on the platform; the control terminal controls the femtosecond laser, the spatial optical path, and the processing platform to ensure that the entire printing process proceeds safely and normally. Before printing, the control terminal uses software to slice the model layer by layer in the horizontal direction and generate the scanning trajectory of each slice. During the printing process, the control terminal controls the galvanometer in the spatial optical path and the electrically controlled displacement platform in the processing platform to ensure that the laser spot moves inside the sample according to the scanning trajectory generated by the software. After each slice is printed, the electrically controlled displacement platform moves the sample a set distance in the vertical direction before printing the next slice, until all slices are printed.

[0010] Specifically, the spatial optical path includes a galvanometer, a scanning lens, a barrel lens, a reflecting mirror, a dichroic mirror, and an objective lens through which the laser passes in sequence, used to transmit pulsed laser light, control the direction of the laser light, and focus the laser light onto the sample. The process involves a femtosecond laser outputting pulsed laser light to a galvanometer, which then controls the laser to scan according to a scanning trajectory generated by a control terminal. A scanning lens focuses the laser light emitted from the galvanometer. A barrel lens relays the focal point, extending the laser transmission distance. The pulsed laser light is reflected by a mirror and then passes through a dichroic mirror to enter the objective lens. The objective lens focuses the laser light onto the part of the sample that needs to be processed. The dichroic mirror also reflects illumination light to monitor the printing process.

[0011] Specifically, the processing platform includes an electrically controlled displacement platform that can move in the X, Y, and Z directions, used to carry the sample and position it in the X, Y, and Z directions. The X and Y axes of the electrically controlled displacement platform control the movement of the sample stage in two orthogonal horizontal directions, respectively, while the Z axis controls the movement of the sample stage in the vertical direction. The included angles between any two X, Y, and Z axes are 90°. After each layer of slices is printed, the electrically controlled displacement platform moves the sample stage vertically a set distance before printing the next layer of slices.

[0012] Specifically, the control terminal is connected to the femtosecond laser, the spatial optical path, and the processing platform, respectively, and is used to comprehensively control the printing process. Its functions are as follows: The control terminal is used to control the high repetition rate femtosecond laser seed source, pulse modulator, and pulse amplifier in the femtosecond laser, including turning the laser seed source and each amplifier on and off, as well as adjusting the current; the control terminal also controls the pulse modulator to modulate the pulse.

[0013] By coordinating the pulse modulator and the pulse amplifier, the average and peak power of the pulsed laser in the input wavelength tuning module of the femtosecond laser can be adjusted, thereby enabling separate adjustment of the supercontinuum width and laser power output from the photonic crystal fiber in the tunable filter module.

[0014] The control terminal is also used to adjust the processing platform to ensure that the initial position of the laser spot is inside the sample; and to control the deflection of the galvanometer in the spatial optical path to ensure that the laser spot scans inside the sample according to the trajectory generated by the software; at the same time, it controls the trajectory of the electrically controlled displacement platform in the processing platform to ensure high-precision positioning during the printing process.

[0015] Furthermore, the high repetition rate femtosecond laser seed source has a repetition frequency ≥ 1 GHz; The tunable filter module includes a three-dimensional fiber adjustment frame, an optical support, a fiber clamp, a photonic crystal fiber, a lens, a tunable filter, and an attenuator.

[0016] The frequency-doubled laser output from the frequency doubling module is coupled through a collimator on a three-dimensional fiber adjustment frame, then enters a photonic crystal fiber. After exciting a supercontinuum, it is output into free space, collimated by a lens, filtered by a tunable filter, and then emitted through an attenuator. Adjusting the transmission band of the tunable filter allows for selective filtering of the output pulsed laser at the target wavelength, while filtering out frequency-doubled light that has not undergone frequency conversion. The two ends of the photonic crystal fiber are fixed to the optical support by fiber clamps. Adjusting the attenuator allows for adjustment of the output light intensity.

[0017] This invention utilizes a commercially available photonic crystal fiber for efficiently exciting supercontinuum spectra, typically possessing two or more zero-dispersion points. The pump wavelength can fall within the anomalous dispersion region between the two zero-dispersion points. In this region, the pump-excited higher-order soliton splitting simultaneously excites a dispersive wave in the short-wavelength direction and, through a soliton self-frequency shift effect, excites new frequency components in the long-wavelength direction. By adjusting the relative position to the two zero-dispersion points, the width of the dispersive wave and the amount of soliton self-frequency shift (the dispersive wave is broadband) can be effectively controlled, i.e., the width of the spectral extension in both the short and long-wavelength directions.

[0018] The photonic crystal fiber has a length of 2-4 m. At this length, sufficient nonlinear effects can be accumulated and spectral broadening can be achieved, while avoiding loss accumulation due to excessive fiber length, and avoiding energy dissipation or spectral recompression caused by stimulated Raman scattering.

[0019] The tunable filter module outputs a pulsed laser with a wavelength tuning range of 500-800 nm, a spectral bandwidth of 3 dB ≤ 1 nm, and a continuously adjustable wavelength with a tuning accuracy of ≤ 1 nm.

[0020] Compared with the prior art, the advantages of the present invention are as follows: The output spectrum covers an ultra-wide range from ultraviolet to infrared with extremely flexible wavelength switching, much like an ultra-wide "laser palette." By adjusting the transmission band of the tunable filter, the output wavelength can be continuously adjusted within a range of 500-800nm, adapting to the optimal two-photon absorption wavelength for different materials. When processing different photoresists, simply adjusting the wavelength filtered out by the filter allows for easy and rapid selection of the desired target wavelength. Multiple photolithography processes can be implemented on a single device without replacing the entire laser source for each material, achieving multi-functional integration. This enables the processing of complex three-dimensional micro / nano structures requiring multiple materials and steps, accelerates the exploration of the "optimal process window" for new materials, and greatly promotes the collaborative development of new materials and processes. By scanning different wavelengths, more efficient excitation wavelengths for the photochemical reactions of new materials can be screened, and the two-photon absorption cross-section of new materials at different wavelengths can be accurately measured, providing crucial data for material formulation optimization. For photoresists with different polymerization mechanisms, the optimal wavelength can be flexibly matched to achieve the best degree of polymerization and resolution. This allows researchers to design new photoresists with broad spectral response and high photosensitivity, freeing them from the limitations of a single wavelength of light source, thereby enriching the variety of processable materials.

[0021] The high-repetition-rate femtosecond laser used has the following advantages compared to low-repetition-rate lasers: With the same average power, the single pulse energy is lower, which can effectively avoid competing nonlinear effects such as stimulated Raman scattering and stimulated Brillouin scattering excited by high peak power in optical fibers. This makes the generation of the supercontinuum mainly rely on soliton self-frequency shift and spectral broadening generated by dispersive waves, thus making the supercontinuum smoother, more coherent, and with lower time-domain background noise.

[0022] With the same average power, the single pulse energy is lower, and the energy is injected into the waveguide in a more uniform quasi-continuous form, which can make the waveguide temperature distribution more uniform, the peak heat load low, effectively avoid phase mismatch and power drift caused by thermal lensing effect, and ensure the long-term stability of the spectrum and power of the supercontinuum.

[0023] High-repetition-rate laser pulses have extremely short intervals. The acoustic field, thermal field, or particle population excited by the previous pulse can affect the nonlinear evolution of subsequent pulses, which can be used for spectral shaping and noise suppression. High-repetition-rate solitons can form bound states and soliton molecules through interactions. Their supercontinuum characteristics are different from those of single solitons, which can provide new degrees of freedom for spectral manipulation. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a wavelength-tunable high-repetition-rate femtosecond laser based on the supercontinuum effect and the two-photon lithography system thereof, as described in an embodiment of the present invention.

[0025] Figure 2This is a schematic diagram of the structure of a femtosecond laser in an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of the tunable filter module used in the femtosecond laser in an embodiment of the present invention.

[0027] Figure 4 This is the spectrum of the 742 nm laser output by the tunable filter module in this embodiment of the invention.

[0028] Figure 5 This is the spectrum of the 556 nm laser output by the tunable filter module in this embodiment of the invention.

[0029] Figure 6 This is a structural diagram of the spatial optical path and processing platform in an embodiment of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] like Figure 2 As shown in the embodiment of the present invention, a wavelength-tunable high-repetition-rate femtosecond laser based on the supercontinuum effect is provided. The femtosecond laser 101 includes a high-repetition-rate femtosecond laser seed source 201, a pulse modulator 202, a pulse amplifier 203, a frequency doubling module 204, and a tunable filter module 205 connected in sequence. In one embodiment, the high-repetition-rate femtosecond laser seed source 201 outputs a pulsed laser with a wavelength of 1.5 μm. The duty cycle of the pulse modulator 202 is set to adjust the peak power of the pulsed laser. The pulse amplifier 203 then amplifies the power of the pulsed laser. Subsequently, the frequency doubling module 203 generates a pulsed laser with a wavelength of 780 nm and filters out the 1.5 μm fundamental frequency light. The supercontinuum is excited by the photonic crystal fiber 304 in the tunable filter module 204. The transmission band of the tunable filter 306 in the tunable filter module 205 is adjusted to achieve a filtered output wavelength of 500-800 nm. A continuously tunable femtosecond laser within the nm range, filtering out lasers with a wavelength of 780 nm that do not undergo frequency conversion.

[0032] By adopting a passive tuning method, the wavelength is first tunable by generating a broadband, supercontinuous spectral output and then filtering to obtain the required narrowband wavelength components.

[0033] like Figure 3As shown, the tunable filter module 205 in the femtosecond laser 101 includes a collimator, an optical support 302, an optical fiber clamp 303, a photonic crystal fiber 304, a lens 305, a tunable filter 306, and an attenuator 307. The collimator is mounted on the three-dimensional optical fiber adjustment frame 301. The collimator, photonic crystal fiber 304, lens 305, tunable filter 306, and attenuator 307 are arranged sequentially, and both ends of the photonic crystal fiber 304 are fixed to the optical support 302 by the optical fiber clamp 302. The frequency-doubled laser output from the frequency doubling module 203 is coupled by a commercially available collimator mounted on the three-dimensional optical fiber adjustment frame 301, then enters the photonic crystal fiber 304, excites a supercontinuum, and is output into free space. After being collimated by the lens 305 and filtered by the tunable filter 306, it exits through the attenuator 307. Adjusting the transmission band of the tunable filter 306 allows for selective filtering of the target wavelength pulsed laser output and filtering out the 780 nm laser that has not undergone frequency conversion; adjusting the attenuator 307 allows for adjustment of the output light intensity.

[0034] Photonic crystal fibers with double or even multiple zero-dispersion points are selected to cover a wider spectrum. The length of these photonic crystal fibers is on the order of meters or even longer. Longer photonic crystal fibers allow for the cascading accumulation of various nonlinear effects, such as self-phase modulation, soliton splitting, Raman scattering, and four-wave mixing, gradually expanding the spectrum from the pump wavelength to both sides. The interaction between different modes can further extend the spectral width. Femtosecond, picosecond, or even nanosecond and continuous-wave pump sources can be input into the photonic crystal fiber, generating spectral broadening through different physical mechanisms. The photonic crystal fiber used primarily operates in multimode, further extending the spectral width through the interaction between different modes. The output of the photonic crystal fiber is a broad and continuous spectrum with high flatness.

[0035] In one embodiment, the photonic crystal fiber has a length of 2-4 m. At this length, sufficient nonlinear effects can be accumulated and spectral broadening can be achieved, while avoiding loss accumulation due to excessive fiber length, and avoiding energy dissipation or spectral recompression caused by stimulated Raman scattering.

[0036] In one embodiment, the nonlinear coefficient of the photonic crystal fiber is ≥40 W / km to promote the full generation and interaction of various nonlinear effects, thereby achieving a wide range of spectral broadening; the dispersion value of the photonic crystal fiber in the target broadened wavelength band... β 2 is ±1 to ±50 ps² / km and flat; the loss of the photonic crystal fiber in the target output band is ≤0.01 dB / m and flat.

[0037] This invention provides a two-photon lithography system, such as... Figure 1As shown, the system includes the femtosecond laser 101, spatial optical path 102, processing platform 103, and control terminal 104 provided in the aforementioned embodiments. The control terminal 104 is connected to the femtosecond laser 101, spatial optical path 102, and processing platform 103.

[0038] The femtosecond laser output by the femtosecond laser 101 is transmitted to the processing platform 103 via the spatial optical path 102 to process the photoresist placed on the processing platform 103; the control terminal 104 controls the femtosecond laser 101, the spatial optical path 102 and the processing platform 103 respectively to ensure that the entire printing process is safe and normal.

[0039] In one embodiment, the femtosecond laser 101 outputs a femtosecond laser with a wavelength tunable in the range of 500-800 nm.

[0040] Before printing, the control terminal 104 uses software (existing software, which will not be described in detail here) to slice the model layer by layer in the horizontal direction and generate the scanning trajectory of each slice. During the printing process, the control terminal 104 controls the galvanometer 501 in the spatial optical path 102 and the electrically controlled displacement platform in the processing platform 103 to ensure that the laser spot moves inside the sample according to the generated scanning trajectory. After each layer of slices is printed, the electrically controlled displacement platform moves the sample a set distance in the vertical direction before printing the next layer of slices, until all slices are printed.

[0041] In one embodiment, such as Figure 6 As shown, the spatial optical path 102 includes a galvanometer 501, a scanning lens 502, a barrel lens 503, a reflecting mirror 504, a dichroic mirror 505, and an objective lens 506 through which the laser passes in sequence. It is used to transmit pulsed laser light, control the direction of the laser light, and focus the laser light onto the sample. The femtosecond laser 101 outputs pulsed laser light to the galvanometer 501, which controls the laser to scan according to the scanning trajectory generated by the control terminal 104. The scanning lens 502 focuses the laser light emitted from the galvanometer 501. The barrel lens 503 relays the focus point, extending the laser transmission distance. The pulsed laser light is reflected by the reflecting mirror 504 and passes through the dichroic mirror 505 before entering the objective lens 506. The objective lens 506 focuses the laser light onto the position in the sample to be processed. The dichroic mirror 505 simultaneously reflects the illumination light used to monitor the printing process.

[0042] In one embodiment, the processing platform 103 includes an electrically controlled displacement platform and a sample stage. The sample stage can move in the X, Y, and Z directions under the drive of the electrically controlled displacement platform. The sample stage is used to carry the sample and is positioned in the X, Y, and Z directions by carrying the sample through the electrically controlled displacement platform.

[0043] In one embodiment, the X-axis and Y-axis of the electrically controlled displacement platform control the sample stage to move in two orthogonal horizontal directions, and the Z-axis controls the sample stage to move in the vertical direction; the included angle between each pair of the X-axis, Y-axis, and Z-axis is 90°; after each layer of slice is printed, the electrically controlled displacement platform drives the sample stage to move vertically a set distance before printing the next layer of slice.

[0044] The control terminal 104 is connected to the femtosecond laser 101, the spatial optical path 102, and the processing platform 103, and is used to control the entire printing process, as follows: The control terminal 104 controls the high repetition rate femtosecond laser seed source 201 and pulse amplifier 203 in the femtosecond laser 101, including turning on and off each pump and adjusting the current therein; the control terminal 104 also controls the pulse modulator 202 to modulate the pulse.

[0045] By coordinating the pulse modulator 202 and the pulse amplifier 203, the average power and peak power of the pulsed laser input to the tunable filter module 205 of the frequency multiplication module 204 can be adjusted, thereby realizing the separate adjustment of the supercontinuum width and laser power output from the photonic crystal fiber in the tunable filter module 205.

[0046] The control terminal 104 is also used to adjust the electrically controlled displacement platform in the processing platform 103 to ensure that the starting position of the laser spot is inside the sample, and to control the deflection of the galvanometer 501 in the spatial optical path 102 to ensure that the laser spot scans on the sample surface according to the generated trajectory; at the same time, it controls the trajectory of the electrically controlled displacement platform in the processing platform 103 to ensure high-precision positioning during the printing process.

[0047] In one embodiment, the pulsed laser output by the tunable filter module 204 has a wavelength tuning range of 500-800 nm, a spectral 3 dB bandwidth of 0.9 nm, and the wavelength is continuously adjustable with a tuning accuracy of 0.4 nm. The spectra of different wavelength lasers output by the tunable filter module 204 are as follows: Figure 4 As shown.

[0048] The light source of this invention has advantages such as tunable wavelength and high repetition frequency. It can select the appropriate processing laser wavelength according to different photoresist materials, thereby achieving lower laser power requirements, faster printing speed, and less material damage.

[0049] In one embodiment, the photoresist material to be processed uses phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide as a photoinitiator, and the specific technical solution is as follows: Femtosecond laser 101 outputs pulsed laser with a repetition rate of 1.0 GHz. The high-repetition-rate femtosecond laser seed source 201 is turned on and allowed to self-start. Then, the pulse modulator 202 is adjusted to set the duty cycle of the pulse train to 1%, ensuring a high peak power to fully utilize various nonlinear effects and excite the supercontinuum. Subsequently, each stage of the amplifiers in the pulse amplifier 203 is turned on sequentially to amplify the pulsed laser power to 1 W. After frequency doubling by the frequency multiplier module 204 to generate a 780 nm pulsed laser and filtering out the 1.5 μm fundamental frequency light, the laser enters the tunable filter module 205 to excite a supercontinuum covering wavelengths of thousands of nanometers. The transmission band of the tunable filter 306 is adjusted to extract the 742 nm target wavelength component from the supercontinuum. The attenuation ratio of the attenuator 307 is adjusted to 40%, finally obtaining a pulsed laser with a wavelength of 742 nm and a pulse width of 300 fs. Its spectrum is shown in the figure. Figure 4 As shown. The pulsed laser is incident on the galvanometer 501, which controls the laser to scan according to the scanning trajectory generated by the control terminal 104. After being focused by the scanning lens 502, the beam passes through the barrel lens 503, is reflected by the mirror 504, passes through the dichroic mirror 505, and is focused by the objective lens 506 onto the photoresist at the bottom of the glass slide. The control terminal 104 positions the photoresist interface and controls the movement of the processing platform 103 so that the processing position is located inside the sample. The software imports the structural model to be printed and generates the scanning trajectory for each layer of the model. The control terminal 104 controls the galvanometer 501 and the electrically controlled displacement platform to make the laser spot scan layer by layer in a "bow" shape according to the predetermined trajectory. After each layer is printed, the electrically controlled displacement platform moves the sample stage vertically a set distance until all slices are printed.

[0050] In another embodiment, the photoresist to be processed uses 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone as a photoinitiator, and the specific technical solution is as follows: In this embodiment, the femtosecond laser 101 outputs a pulsed laser with a repetition rate of 1.0 GHz. The high-repetition-rate femtosecond laser seed source 201 is turned on and allowed to self-start. Then, the pulse modulator 202 is adjusted to set the duty cycle of the pulse train to 1%, ensuring a high peak power to fully utilize various nonlinear effects and excite the supercontinuum. Subsequently, each stage of the amplifiers in the pulse amplifier 203 is turned on sequentially to amplify the pulsed laser power to 1 W. After frequency doubling by the frequency multiplier module 204 to generate a 780 nm pulsed laser and filtering out the 1.5 μm fundamental frequency light, the laser enters the tunable filter module 205, exciting a supercontinuum covering wavelengths of thousands of nanometers. The transmission band of the tunable filter 306 is adjusted to extract the 556 nm target wavelength component from the supercontinuum. The attenuation ratio of the attenuator is adjusted to 0%, ultimately obtaining a pulsed laser with a wavelength of 556 nm and a pulse width of 300 fs, as shown in the spectrum. Figure 5 As shown. The pulsed laser is incident on the galvanometer 501, which controls the laser to scan according to the scanning trajectory generated by the control terminal 104. After being focused by the scanning lens 502, the beam passes through the barrel lens 503, is reflected by the mirror 504, passes through the dichroic mirror 505, and is focused by the objective lens 506 onto the photoresist at the bottom of the glass slide. The control terminal 104 positions the photoresist interface and controls the movement of the processing platform 103 so that the processing position is located within the sample. The model is imported into the software, and the software generates the scanning trajectory for each layer of the model. The control terminal 104 controls the galvanometer 501 and the electrically controlled displacement platform according to the program, so that the laser spot scans layer by layer in a "bow" shape according to the predetermined trajectory. After each layer is printed, the electrically controlled displacement platform moves the sample stage vertically a set distance until all slices are printed.

[0051] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined in this invention may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wavelength-tunable high-repetition-rate femtosecond laser based on the supercontinuum effect, characterized in that, It includes a high-repetition-rate femtosecond laser seed source, a pulse modulator, a pulse amplifier, a frequency doubling module, and a tunable filter module; The high-repetition-rate femtosecond laser seed source, pulse modulator, pulse amplifier, frequency doubling module, and tunable filter module are arranged sequentially. The high-repetition-rate femtosecond laser seed source is used to output pulsed laser, the pulse modulator is used to adjust the peak power of the pulsed laser, the pulse amplifier is used to amplify the power of the pulsed laser, the frequency doubling module is used to double the frequency of the pulsed laser and filter out the fundamental frequency light, and the tunable filter module is used to excite the supercontinuum and achieve continuous adjustment of the output wavelength by adjusting the transmission band.

2. The wavelength-tunable high-repetition-rate femtosecond laser based on the supercontinuum effect according to claim 1, characterized in that, The tunable filtering module includes a collimator, a photonic crystal fiber, a lens, a tunable filter, and an attenuator arranged sequentially. The collimator is used to couple the input frequency-doubled laser, the photonic crystal fiber is used to excite the supercontinuum, the lens is used to collimate the supercontinuum, the tunable filter is used to filter the supercontinuum to adjust the transmission band and output femtosecond laser of the target wavelength, and the attenuator is used to adjust the output light intensity. The photonic crystal fiber has two or more zero dispersion points and outputs a wide and continuous spectrum.

3. A wavelength-tunable high-repetition-rate femtosecond laser based on the supercontinuum effect according to claim 2, characterized in that, The length of the photonic crystal fiber is 2-4 m.

4. A wavelength-tunable high-repetition-rate femtosecond laser based on the supercontinuum effect according to claim 2, characterized in that, The nonlinear coefficient of the photonic crystal fiber is ≥40 W / km.

5. A wavelength-tunable high-repetition-rate femtosecond laser based on the supercontinuum effect according to claim 2, characterized in that, By using a pump source with femtosecond, picosecond, or nanosecond continuous waves to input into a photonic crystal fiber, spectral broadening is generated through different physical mechanisms.

6. A wavelength-tunable high-repetition-rate femtosecond laser based on the supercontinuum effect according to claim 2, characterized in that, The tunable filter module also includes a three-dimensional fiber adjustment frame, an optical support, and fiber clamps. The collimator is mounted on the three-dimensional fiber adjustment frame, and the photonic crystal fiber is mounted on the optical support via the fiber clamps.

7. A wavelength-tunable high-repetition-rate femtosecond laser based on the supercontinuum effect according to any one of claims 1-6, characterized in that, The femtosecond laser outputs a femtosecond laser with a continuously adjustable wavelength in the range of 500-800 nm.

8. A two-photon lithography system, characterized in that, The invention includes the femtosecond laser, spatial optical path, processing platform, and control terminal as described in any one of claims 1-7. The femtosecond laser output from the femtosecond laser is transmitted to the processing platform via the spatial optical path to process the sample placed on the processing platform. The femtosecond laser, spatial optical path, and processing platform are all connected to the control terminal.

9. A two-photon lithography system according to claim 8, characterized in that, The spatial optical path is used to transmit pulsed laser light, control the direction of the laser light, and focus the laser light into the sample. It includes a galvanometer, a scanning lens, a barrel lens, a reflecting mirror, a dichroic mirror, and an objective lens through which the laser light passes in sequence. The objective lens is used to focus the laser light onto the position in the sample that needs to be processed, and the dichroic mirror can reflect the illumination light used to monitor the printing process.

10. A two-photon lithography system according to claim 8, characterized in that, The processing platform 103 includes an electrically controlled displacement platform and a sample stage driven by the electrically controlled displacement platform.

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