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

Abstract

The application discloses a wavelength-tunable high-repetition-rate femtosecond laser based on dispersion wave effect and a two-photon photoetch system. The system comprises a femtosecond laser, a spatial light path, a processing platform and a control terminal. The femtosecond laser stimulates dispersion waves with different degrees of frequency shift by cooperatively adjusting the pulse sequence and average power of laser inputted into a photonic crystal fiber, outputs high-repetition-rate pulsed laser with a wavelength tunable in a range from 500 nm to 800 nm, and focuses the laser into photoresist by the spatial light path for processing. The control terminal is connected with the femtosecond laser, the spatial light path and the processing platform respectively, and is used for controlling the whole printing process. The light source has the advantages of wavelength tunable and high repetition frequency, can select a suitable processing laser wavelength according to different photoresist materials, and realizes lower laser power requirement, faster printing speed and less material damage.

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 dispersive wave 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 dispersive wave effect, which can achieve adaptive two-photon lithography for different materials by tuning the wavelength.

[0005] This invention utilizes the highly nonlinear characteristics of photonic crystal fibers. By altering the phase-matching condition between the soliton and the dispersive wave, a frequency shift is generated in the output laser, thereby achieving continuous wavelength tuning. The specific principle is as follows: By increasing the peak power of the laser incident on the photonic crystal fiber, the peak power of the fundamental soliton formed in the fiber will also increase. According to the soliton's characteristics, its pulse width will correspondingly narrow. The combined effect of these two factors significantly enhances the nonlinear phase shift generated by the soliton, disrupting the original phase-matching equilibrium. In the normal dispersion region where the dispersive wave resides, the propagation constant increases with increasing frequency. To rebuild the equilibrium, the new phase-matching point tends to shift towards higher frequencies. This dynamic process causes a blue shift in the wavelength of the dispersive wave as the laser power incident on the photonic crystal fiber increases, and vice versa.

[0006] Modulating the laser pulse sequence allows adjustment of the peak power of the pulsed laser, enabling the change of the output laser wavelength from the photonic crystal fiber without altering the average power of the laser input to the fiber. Simultaneously, coordinating the pulse sequence and average power of the pulsed laser input to the photonic crystal fiber allows for adjustment of the output laser power without changing the output laser wavelength.

[0007] The present invention is achieved by at least one of the following technical solutions.

[0008] A wavelength-tunable high-repetition-rate femtosecond laser based on the dispersive wave effect includes a high-repetition-rate femtosecond laser seed source, a pulse modulator, a pulse amplifier, a frequency doubling module, and a wavelength tuning module connected in sequence. 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 laser, and the wavelength tuning module is used to excite dispersive waves of different wavelengths and filter and output laser of the target wavelength.

[0009] 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, and the peak power of the pulsed laser is adjusted. Then, the pulse amplifier is adjusted to amplify the power of the pulsed laser. Next, the frequency doubling module doubles the laser frequency and filters out the fundamental frequency light. Finally, the current of the main amplifier in the pulse amplifier is adjusted by the control terminal, and the average laser power of the photonic crystal fiber in the input wavelength tuning module is adjusted to excite dispersive waves of different wavelengths. After the filter removes the frequency-doubled light that has not undergone frequency conversion, the output laser wavelength is continuously adjustable in the range of 500-800 nm.

[0010] A two-photon lithography system includes a 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 processing platform; the control terminal is connected to the femtosecond laser, the spatial optical path and the processing platform respectively to control the entire printing process; 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.

[0011] 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 femtosecond laser outputs pulsed laser light to the galvanometer, which controls the laser to scan according to the scanning trajectory generated by the control terminal. The scanning lens focuses the laser light emitted from the galvanometer. The barrel lens relays the focal point, extending the laser transmission distance. The pulsed laser light is reflected by the mirror and passes through the dichroic mirror to enter the objective lens. The objective lens is used to focus the laser light to the position in the sample that needs to be processed. The dichroic mirror also reflects the illumination light for monitoring the printing process.

[0012] 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 sample stage to move in two orthogonal horizontal directions, while the Z axis controls the sample stage to move 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.

[0013] Specifically, the control terminal is connected to the femtosecond laser, the spatial optical path, and the processing platform 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 and pulse amplifier in the femtosecond laser, including turning the laser seed source and each amplifier on and off, and adjusting the current; the control terminal also controls the pulse modulator to modulate the pulse.

[0014] By coordinating the pulse modulator and the pulse amplifier, the average power and peak power of the pulsed laser input to the wavelength tuning module of the frequency doubling module can be adjusted, thereby achieving separate adjustment of the wavelength and power of the pulsed laser output by the wavelength tuning module.

[0015] The control terminal is also used to adjust the processing platform to ensure that the starting 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.

[0016] Furthermore, the high repetition rate femtosecond laser seed source has a repetition frequency ≥ 1 GHz; The wavelength tuning module in the femtosecond laser includes a three-dimensional fiber adjustment frame, an optical support, fiber optic clamps, a photonic crystal fiber, a lens, a filter, and an attenuator.

[0017] The frequency-doubled laser output from the frequency doubling module is coupled through a collimator on a three-dimensional fiber adjustment frame, and then enters a photonic crystal fiber. After exciting a dispersive wave of a specific wavelength related to the incident light power, it is output into free space, collimated by a lens, filtered to remove the frequency-doubled light that has not undergone frequency transformation, and then emitted through an attenuator. The two ends of the photonic crystal fiber are fixed to the optical support by fiber clamps; the output light intensity can be adjusted by adjusting the attenuator.

[0018] A commercially available photonic crystal fiber for efficiently exciting dispersive waves is selected. The zero-dispersion wavelength of the photonic crystal fiber is shorter than the wavelength of the incident light, which is the wavelength of the frequency-doubled laser output by the frequency doubling module. This allows the incident light to propagate in the anomalous dispersion region of the photonic crystal fiber. By adjusting the peak power of the incident light, phase matching with the normal dispersion region is achieved through the soliton self-frequency shift effect, precisely exciting a narrowband dispersive wave of the target wavelength, while suppressing dispersive waves of other wavelength components to avoid generating a broadband spectrum. The wavelength tuning module outputs a pulsed laser with a wavelength tuning range of 500-800 nm, a spectral 3 dB bandwidth of ≤1 nm, and a continuously adjustable wavelength with a tuning accuracy of ≤1 nm.

[0019] Compared with the prior art, the advantages of this invention are: The output wavelength is continuously adjustable, with a tuning range of 500-800 nm, and can be adapted to the optimal two-photon absorption wavelength of different materials, thereby improving printing accuracy, processing efficiency, and material and process compatibility. The core advantage of this technology lies in its extremely high single-band conversion efficiency, which can efficiently concentrate the energy of femtosecond pulses to specific target bands in the deep ultraviolet and mid-infrared.

[0020] For special functional materials that are completely unresponsive to ordinary photoresists but require specific wavelengths to cure, this solution can provide a powerful "hard-hitting" light source, empowering the development of specific new materials.

[0021] This approach can achieve the highest efficiency when the material being processed is particularly sensitive to a specific optimal wavelength, thereby improving the processing efficiency of that material.

[0022] The output is a single target wavelength, and the subsequent optical system does not require complex beam splitting components, which simplifies system design and facilitates system integration.

[0023] The high-repetition-rate femtosecond laser of this application has the following advantages compared with 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 dispersive waves excited by photonic crystal fibers smoother, more coherent, and with lower time-domain background noise.

[0024] 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 is low, effectively avoid phase mismatch and power drift caused by thermal lensing effect, and ensure the long-term stability of output laser wavelength and power.

[0025] High repetition rate lasers have extremely short pulse intervals. The dispersive wave generated by the previous pulse will coherently interact with the subsequent pump pulse or soliton. By utilizing this relationship, the generation of the dispersive wave can be periodically resonated with the pump pulse sequence, thereby significantly improving the conversion efficiency from pump light to dispersive wave. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a wavelength-tunable high-repetition-rate femtosecond laser based on the dispersive wave effect and the two-photon lithography system thereof, as described in an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the structure of a femtosecond laser in an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the wavelength tuning module used in the femtosecond laser in an embodiment of the present invention.

[0029] Figure 4 This is the spectrum of the 742 nm laser output by the wavelength tuning module in this embodiment of the invention.

[0030] Figure 5 This is the spectrum of the 556 nm laser output by the wavelength tuning module in this embodiment of the invention.

[0031] Figure 6 This is a structural diagram of the spatial optical path and processing platform in an embodiment of the present invention. Detailed Implementation

[0032] 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.

[0033] like Figure 2 As shown in the figure, the present invention provides a wavelength-tunable high repetition rate femtosecond laser based on the dispersive wave effect, namely, 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 wavelength tuning module 205 connected in sequence.

[0034] In one embodiment, the high-repetition-rate femtosecond laser seed source 201 outputs a pulsed laser with a wavelength of 1.5 μm. First, the duty cycle of the pulse modulator 202 is set to adjust the peak power of the pulsed laser. Then, the power of the pulsed laser is amplified by the pulse amplifier 203. After that, the laser is frequency doubled by the frequency doubling module 204 to generate a laser with a wavelength of 780 nm and filter out the 1.5 μm wavelength as the fundamental frequency light. Finally, the current of the main amplifier in the pulse amplifier 203 is adjusted by the control terminal 104 to adjust the average laser power of the photonic crystal fiber 304 in the input wavelength tuning module 205, thereby exciting dispersive waves of different wavelengths. The 780 nm wavelength laser that has not undergone frequency conversion is filtered out by the filter 306 in the wavelength tuning module 205, and the output laser with a continuously adjustable wavelength is generated.

[0035] The wavelength tuning module 204 outputs a pulsed laser with a wavelength tuning range of 500-800 nm, a spectral 3 dB bandwidth of 0.8 nm, and a continuously adjustable wavelength with a tuning accuracy of 0.3 nm.

[0036] like Figure 3 As shown, the wavelength tuning module 205 includes a three-dimensional fiber adjustment frame 301, an optical support 302, a fiber clamp 303, a photonic crystal fiber 304, a lens 305, a filter 306, and an adjustable attenuator 307.

[0037] The frequency-doubled laser output from the frequency-doubled module 204 is coupled through a commercial collimator on the three-dimensional fiber adjustment frame 301, and then enters the photonic crystal fiber 304. After exciting a dispersive wave of a specific wavelength proportional to the peak power of the incident light, i.e. the frequency-doubled laser, it is output into free space. After being collimated by the lens 305, the laser with a wavelength of 780 nm is filtered out by the filter 306 and then emitted through the adjustable attenuator 307. The two ends of the photonic crystal fiber 304 are fixed to the optical bracket 302 by the fiber clamps 303. The output light intensity can be adjusted by adjusting the adjustable attenuator 307.

[0038] In one embodiment, the length of the photonic crystal fiber is 20-50 cm. At this length, sufficient nonlinear effects can be accumulated to effectively excite dispersive waves, while avoiding additional losses and competing nonlinear effects such as stimulated Raman scattering introduced by excessive fiber length, and avoiding wavelength drift or broadening of dispersive waves caused by nonlinear effects, which would damage the narrowband characteristics of the output.

[0039] In one embodiment, the nonlinear coefficient of the photonic crystal fiber is ≥20 W / km; the loss of the photonic crystal fiber at the pump wavelength and the target dispersive wavelength is ≤0.1 dB / m.

[0040] In this embodiment of the invention, the photonic crystal fiber used has a single zero-dispersion point, which is pumped to the anomalous dispersion region and radiates dispersive waves into the normal dispersion region. An active tuning method is employed, utilizing a specific physical mechanism to change the pump power or fine-tune the pump wavelength, adjusting the soliton-dispersive wave phase matching condition to generate the target wavelength. Phase-matched radiation between the soliton and the dispersive wave is achieved using a centimeter-scale photonic crystal fiber, avoiding the generation of higher-order nonlinear effects caused by excessively long fibers, such as stimulated Raman scattering and self-steepening, which would exacerbate soliton redshift, leading to wavelength drift or broadening of the dispersive wave and compromising the narrowband characteristics of the output. Femtosecond-scale ultrashort pulses are used to input the photonic crystal fiber to provide the extremely high instantaneous power required for soliton splitting, ensuring wavelength purity and stability. The photonic crystal fiber primarily operates in single mode, ensuring a single, clean mode for frequency conversion. The output spectrum of the photonic crystal fiber exhibits one or several discrete and extremely narrow peaks, demonstrating excellent signal-to-noise ratio and stability.

[0041] This invention provides a two-photon lithography system, such as... Figure 1 As shown, it includes the femtosecond laser 101, spatial optical path 102, processing platform 103 and control terminal 104 provided in the aforementioned embodiments.

[0042] The femtosecond laser 101 outputs a femtosecond laser with a wavelength tunable in the range of 500-800 nm. The laser 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 is connected to the femtosecond laser 101, the spatial optical path 102 and the processing platform 103 respectively, and is used to control the entire printing process.

[0043] Before printing, the control terminal 104 uses software to slice the structural model to be printed 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 scanning trajectory generated by the software. 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.

[0044] like 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, for transmitting pulsed laser light, controlling the direction of the laser light, and focusing the laser light into the sample.

[0045] In one embodiment, 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 focal point to extend the laser transmission distance; the pulsed laser light is reflected by the mirror 504 and passes through the dichroic mirror 505 before entering the objective lens 506; the objective lens 506 is used to focus the laser light to the position in the sample that needs to be processed; the dichroic mirror 505 also reflects the illumination light for monitoring the printing process.

[0046] The processing platform 103 includes an electrically controlled displacement platform and a sample stage set on the electrically controlled displacement platform. The sample stage can move in the X, Y, and Z directions under the drive of the electrically controlled displacement platform, and can carry the sample and position it in the X, Y, and Z directions.

[0047] The X and Y axes of the electrically controlled displacement platform control the sample stage to move in two orthogonal horizontal directions, while the Z axis controls the sample stage to move 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.

[0048] 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 is used to control the high repetition rate femtosecond laser seed source 201, pulse modulator 202 and pulse amplifier 203 in the femtosecond laser, including turning the laser seed source and each amplifier on and off and adjusting the current; the control terminal 104 also controls the pulse modulator 202 to modulate the pulse.

[0049] By coordinating the pulse modulator 202 and the pulse amplifier 203, the average power and peak power of the laser input to the wavelength tuning module 205 of the frequency multiplication module 204 can be adjusted, thereby realizing the separate adjustment of the wavelength and power of the pulsed laser output by the wavelength tuning module 205.

[0050] The control terminal 104 is also used to adjust 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 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.

[0051] In one embodiment, the photoresist to be processed uses phenylbis(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 100%, keeping the peak power at a low level. This ensures that the subsequently excited dispersive wave produces a small frequency shift relative to the fundamental light, satisfying the phase-matching condition and precisely exciting a narrowband dispersive wave of 742 nm without generating other wavelengths. The amplifiers in pulse amplifier 203 are then sequentially activated to amplify the pulsed laser power to 1 W. After frequency doubling by frequency multiplier module 204 to generate a 780 nm pulsed laser and filtering out the 1.5 μm fundamental light, the laser enters wavelength tuning module 205 to excite a 742 nm narrowband dispersive wave. The attenuation ratio of adjustable attenuator 307 is adjusted to 30%, ultimately 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 collimated 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 structural model to be printed 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.

[0052] In one 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%, resulting in a high peak power. This ensures that the subsequently excited dispersive wave has a large frequency shift relative to the fundamental frequency light, satisfying the phase-matching condition and precisely exciting a narrowband dispersive wave of 556 nm without generating other wavelengths. The amplifiers in the pulse amplifier 203 are then turned on stage by stage 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 wavelength tuning module 205 to excite a 556 nm narrowband dispersive wave. 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 collimated 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, which 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.

[0053] 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 dispersive wave effect, characterized in that, The system includes a high-repetition-rate femtosecond laser seed source, a pulse modulator, a pulse amplifier, a frequency doubling module, and a wavelength tuning module 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 laser, and the wavelength tuning module is used to excite dispersive waves of different wavelengths and filter them to output laser of the target wavelength.

2. The wavelength-tunable high-repetition-rate femtosecond laser based on the dispersive wave effect according to claim 1, characterized in that, The wavelength tuning module includes a collimator, a photonic crystal fiber, a lens, a filter, and an adjustable attenuator arranged sequentially. The frequency-doubled laser output from the frequency-doubled module is coupled into the photonic crystal fiber through the collimator, exciting a dispersive wave of a specific wavelength proportional to the peak power of the frequency-doubled laser. After being collimated by the lens, the non-target wavelength laser is filtered out by the filter, and the target wavelength laser is emitted after passing through the adjustable attenuator. The photonic crystal fiber has a single zero-dispersion point, which is located in the anomalous dispersion region by pumping and radiates dispersive waves into the normal dispersion region.

3. A wavelength-tunable high-repetition-rate femtosecond laser based on the dispersive wave effect according to claim 2, characterized in that, The nonlinear coefficient of the photonic crystal fiber is ≥20 W / km.

4. A wavelength-tunable high-repetition-rate femtosecond laser based on the dispersive wave effect according to claim 2, characterized in that, The length of the photonic crystal fiber is 20-50 cm.

5. A wavelength-tunable high-repetition-rate femtosecond laser based on the dispersive wave effect according to claim 2, characterized in that, It employs femtosecond-level ultrashort pulse input photonic crystal fiber.

6. A wavelength-tunable high-repetition-rate femtosecond laser based on the dispersive wave effect according to claim 2, characterized in that, By adjusting the current of the main amplifier in the pulse amplifier, the average laser power of the photonic crystal fiber in the input wavelength tuning module is adjusted, thereby exciting dispersive waves of different wavelengths.

7. A wavelength-tunable high-repetition-rate femtosecond laser based on the dispersive wave effect according to any one of claims 2-6, characterized in that, The pulse modulator and pulse amplifier are coordinated and controlled, which can adjust the average power and peak power of the laser input to the wavelength tuning module of the frequency doubling module, thereby realizing the separate adjustment of the wavelength and power of the pulsed laser output by the wavelength tuning module 205.

8. A two-photon lithography system, characterized in that, 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 a spatial optical path to process the sample placed on the processing platform. The femtosecond laser, the spatial optical path, and the 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 includes the galvanometer, scanning lens, tube lens, reflecting mirror, dichroic mirror, and objective lens that the laser passes through in sequence.

10. A two-photon lithography system according to claim 8, characterized in that, The processing platform includes an electrically controlled displacement platform and a sample stage set on the electrically controlled displacement platform. The sample stage can move in the X, Y, and Z directions under the drive of the electrically controlled displacement platform.

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