Spectrum optimization and pulse compression system and method based on solid multi-pass cell post-compression

Abstract

According to the spectrum optimization and pulse compression system and method based on solid multi-pass pool post-compression, ultrafast laser pulses output by a laser output module are transmitted back and forth in a spectrum broadening module through an energy regulation and mode matching module, are broadened in a time domain and a frequency domain under the nonlinear effect and the dispersion effect, and are subjected to spectrum optimization and pulse compression; and after being subjected to beam shrinkage and collimation through the light path collimation module, the broadened pulse enters the dispersion compensation module to be subjected to pulse compression. Time-frequency characteristics of laser pulses are measured through the real-time detection module, cross-module multi-parameter collaborative optimization, accurate energy regulation and control, spectrum broadening and dispersion compensation module system parameters are carried out on detection information by adopting the control feedback module, spectrum modulation is inhibited, negative chirp and nonlinear phase distortion of front and rear edges of the pulses are weakened, and the accuracy of the system parameters is improved. And the pulse compression quality is improved. The pulse width of the output compression pulse is close to the Fourier limit, the pulse width is reduced, and the peak power is improved.

Description

Technical Field

[0001] This application relates to the field of ultrafast laser technology, specifically to a spectral optimization and pulse compression system and method based on solid-state multipass cell post-compression. It is primarily applicable to ultrafast lasers, ultraintense and ultrashort lasers, nonlinear optics, and spectroscopy. Background Technology

[0002] In the field of ultrafast laser technology, post-compression systems based on solid-state multipass cells (MPCs) are a method for spectral broadening and pulse compression, and are an important means of obtaining high-power femtosecond pulses. Multipass cells extend the optical path, allowing the light pulse to propagate multiple times in the medium, thus undergoing nonlinear effects and dispersion, achieving spectral broadening and providing a foundation for further pulse compression. However, existing solid-state multipass cell post-compression systems have encountered several technical bottlenecks in the pursuit of ultrashort and ultraintense laser pulses.

[0003] First, gain narrowing limits pulse compressibility. In traditional post-compression systems, when a laser pulse is amplified in the gain medium, spectral broadening is often accompanied by gain curve narrowing due to the non-uniform energy distribution and inherent properties of the gain medium. This results in limited spectral bandwidth, preventing sufficient broadening to the required compression bandwidth, thus limiting the peak power and duration of the compressed pulse.

[0004] Secondly, nonlinear distortion degrades beam quality. During the multiple round trips of the optical pulse through the multipass cell, nonlinear effects exert complex influences on the spectrum, such as self-phase modulation (SPM), cross-phase modulation (XPM), and stimulated Brillouin scattering (SBS). These effects modulate the spectral shape, increase higher-order components of the spectrum, and disrupt the temporal characteristics of the original pulse. This results in an increased pulse width after compression, significant negative chirp at the pulse leading and trailing edges, decreased pulse contrast, and negative pulse temporal quality and compression efficiency.

[0005] Furthermore, high-order dispersion residues and optical damage thresholds limit amplification capabilities. The nonlinear broadening process in a multipass cell is often accompanied by the accumulation of high-order dispersion, such as third-order dispersion (TOD), which leads to efficiency losses during post-pulse compression, potentially causing the compressed pulse width to deviate from the Fourier limit. In addition, when the optical pulse energy exceeds the medium's damage threshold, it can induce minute damage or nonlinear disruption within the medium, further reducing system stability and the upper limit of compressible optical pulse energy.

[0006] In particular, the existence of the relaxation time of the gain medium makes it difficult to obtain an ideal pulse structure during compression, which easily leads to the generation of side pulses. This not only significantly reduces the contrast of the pulse, but may also interfere with the main pulse, affecting the quality and stability of compression. For example, in a 2025 study, VW Segundo Staels et al. proposed a post-compression system with a solid multi-pass cell. Although the scheme achieved spectral broadening through the multi-pass cell, it still has shortcomings in terms of pulse contrast after compression. The energy error caused by the side pulse limits the single pulse energy and reduces the quality of the compressed pulse [Optics Express 33 (11), 23194-23203].

[0007] In summary, existing post-compression systems based on solid-state multipass cells suffer from significant shortcomings in gain mechanisms, nonlinear effect control, higher-order dispersion management, and amplification capabilities. They are particularly ineffective in suppressing spectral distortion, controlling side pulse generation, and improving pulse compression efficiency during pulse compression, which limits their widespread application in high-power femtosecond lasers. Therefore, developing a new method to effectively overcome these shortcomings and achieve high-quality pulse compression is an urgent technical problem to be solved. Summary of the Invention

[0008] The purpose of this invention is to provide a spectral optimization and pulse compression system and method based on solid multipass cell compression. Dynamic optimization is achieved through the linkage of steps such as energy regulation, spectral broadening and dispersion compensation. The time-frequency characteristics of the light pulse during transmission in the MPC are detected in real time. With the help of a control feedback strategy, the total dispersion in the system is precisely matched by regulating the interaction between dispersion and nonlinear effects in the multipass cell, thereby obtaining a high-quality compressed pulse output that approaches the Fourier transform limit.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This application provides a spectral optimization and pulse compression system based on solid-state multi-pass cell post-compression, comprising the following modules: a laser output module, an energy control module, a mode matching module, a spectral broadening module, an optical path collimation module, a dispersion compensation module, a real-time detection module, and a control feedback module. The functions of each module are as follows: Laser output module: The femtosecond laser emits the input laser pulse; Energy control module: The energy control module adjusts the energy of the incident laser pulse generated by the femtosecond laser and transmits it to the mode matching module; Mode matching module: Adjusts the transverse mode of the laser pulse to match the eigenmode of the multipass cell; Spectral broadening module: includes an optical multipass cell and a positive dispersive medium, which is adjusted by the radius of curvature of the concave mirror.R and cavity length L The optical pulse is controlled to travel back and forth within the multipass cell, so that the optical pulse is subjected to nonlinear and dispersion effects each time it passes through the medium, thereby achieving broadening in the frequency and time domains. Optical path collimation module: Composed of a lens group consisting of a plane mirror, a convex lens and a concave lens, it reduces and collimates the beam after it passes through the spectral broadening module. Dispersion compensation module: Adjusts system dispersion, specifically by dynamically adjusting the diffraction grating pair spacing based on the dispersive characteristics of the pulse to be compressed, in conjunction with the real-time detection module. h and beam incident angle i To match the dispersion introduced by the broadening process, ensuring that the output pulse's time width after compression is close to the Fourier limit; Real-time detection module: Used to detect the time-frequency information of ultrafast pulses before and after entering the dispersion compensation module. Specifically, it acquires the time-frequency characteristics of the light pulse by real-time acquisition of the spectral width, phase information and time waveform characteristics of the broadened pulse, evaluates the time-domain and frequency-domain characteristics of the pulse, and transmits the detection information to the control feedback module. The control feedback module, based on the detection data from the real-time detection module, uses a parameter optimization algorithm to determine whether the current system state meets the preset indicators for pulse compression. It coordinates with modules such as energy regulation, spectral broadening, and dispersion compensation to perform cross-module collaborative optimization and adjustment of system parameters to achieve spectral optimization and pulse compression. This includes determining whether the real-time detected pulse time-frequency information matches the theoretically calculated spectrum and Fourier transform-limited pulse width. If they do not match, parameter optimization is performed until the output pulse meets the Fourier transform limit.

[0010] In one embodiment of this application, the laser output module consists of a femtosecond laser responsible for emitting input laser pulses.

[0011] In one embodiment of this application, the energy regulation module includes: a half-wave plate for adjusting the energy of the incident laser pulse; and a polarizing beam splitter for separating and controlling the power distribution ratio of orthogonal polarization components to achieve precise energy regulation.

[0012] In one embodiment of this application, the mode matching module includes a convex lens and a concave lens with a focal length matching the convex lens, and has beam expanding and contracting functions to ensure that the transverse mode of the ultrafast laser matches the eigenmode of the multipass cell; the focal length of the convex lens is... f 1. The focal length of the concave lens is f 2, their relationship is: f 2 = -( oh 1 / oh 0) f 1. Lens spacing is l =f 1(1- oh 1 / oh 0), where, oh 0 represents the input beam radius. oh 1 represents the waist radius after pattern matching, and it must satisfy... f 1 oh 1.

[0013] In one embodiment of this application, the spectral broadening module includes a multipass cell and a positive dispersive medium. The multipass cell consists of a pair of cells with radii of curvature of... R A closed cavity formed by two concave mirrors placed opposite each other, the length of the cavity is... L satisfy R < L <2 R A fused silica medium with positive dispersion properties is placed between two concave mirrors. The ultrafast laser pulse propagates multiple times within the multipass cell, passing through the positive dispersion medium each time and experiencing nonlinear and dispersion effects, resulting in broadening of the ultrafast laser pulse in both the time and frequency domains.

[0014] In one embodiment of this application, the optical path collimation module comprises a plane mirror, a convex lens, and a concave lens, which reduces and collimates the light beam after it passes through the spectral broadening module.

[0015] In one embodiment of this application, the dispersion compensation module includes a diffraction grating pair to perform dispersion compensation on the laser pulse output from the solid multipass cell, that is, to compress the laser pulse in the time domain to obtain an ultrafast laser with a narrower pulse width and higher peak power.

[0016] In one embodiment of this application, the real-time detection module includes a frequency domain analysis system and a time domain analysis system. The frequency domain analysis system acquires the spectral information of the laser pulse, and the time domain analysis system acquires the time domain intensity information of the laser pulse. The time-frequency characteristics of the ultrafast pulse are detected in real time, and the detection information is transmitted to the control feedback module.

[0017] In one embodiment of this application, the control feedback module is responsible for receiving detection information from the real-time detection module, and adjusting the input energy of the pulse through analysis and calculation by the host computer. E laser The radius of curvature of the concave mirror in the spectral broadening module R Cavity length L And the spacing of the diffraction grating pairs in the dispersion compensation module h and the incident angle of the beam of the grating iThis ensures that the dispersion compensation module matches the dispersion increase from the spectral broadening module, guaranteeing that the compressed pulse's time width approaches the Fourier limit. Specific control strategy: Based on the pulse's time-frequency characteristics, the real-time pulse width is adjusted... t test and real-time spectral width Δ l test Compared with theoretical pulse width t theory and theoretical spectral width Δ l theory In comparison, if Δ l test Less than Δ l theory If the spectral broadening is small, it is necessary to adjust the rotation angle of the half-wave plate. α To adjust the input energy of the pulse E laser Simultaneously adjust the radius of curvature of the concave mirror in the spectral broadening module. R Cavity length L To improve the nonlinear effect; further, if t test Greater than t theory Then the dispersion compensation is insufficient, according to t test and t theory Calculate dispersion compensation amount β Adjust the spacing of the diffraction grating pairs in the dispersion compensation module. h and the incident angle of the beam of the grating i This ensures that the amount of dispersion compensated by the dispersion compensation module matches the amount of dispersion increased by the spectral broadening module. This is achieved when Δ... l test ≥Δ l theory and t test ≤ t theory Under these two conditions, the compressed pulse approaches the Fourier transform limit, resulting in an ultrafast output pulse.

[0018] Another aspect of this application provides a spectral optimization and pulse compression method based on solid multi-pass cell compression. This method performs cross-module collaborative optimization on the system described in the first aspect above, achieving dynamic optimization through steps such as energy regulation, spectral broadening, and dispersion compensation. It dynamically adjusts system parameters to achieve the best compression effect, including the following steps: Laser output: The femtosecond laser outputs ultrafast laser pulses; Energy control: The energy of the incident laser pulse generated by the femtosecond laser is adjusted by the energy control module and transmitted to the mode matching module; Mode matching: Adjusting the transverse mode of the laser pulse to match the eigenmode of the multipass cell; Spectral broadening: including optical multipass cells and positive dispersive media, achieved by adjusting the radius of curvature of the concave mirror. R and cavity length L The optical pulse is controlled to travel back and forth within the multipass cell, so that the optical pulse is subjected to nonlinear and dispersion effects each time it passes through the medium, thereby achieving broadening in the frequency and time domains. Optical path collimation: The beam after passing through the spectral broadening module is reduced and collimated for output; Dispersion compensation: Adjust the spacing of the diffraction grating pairs and the incident angle of the beam of the grating to match the amount of dispersion introduced by the broadening process, so as to ensure that the output pulse has a time width close to the Fourier limit after compression. Real-time detection: Real-time acquisition of the spectrum width, phase information and time waveform characteristics of the broadened pulse, and transmission of the detection information to the control feedback module; Control feedback: Based on the detection data from the real-time detection module, determine whether the real-time pulse time-frequency information matches the theoretically calculated spectrum and Fourier transform limit pulse width. If they do not match, optimize the parameters until the output pulse satisfies the Fourier transform limit.

[0019] The advantages of this invention are as follows: This invention proposes a spectral optimization and pulse compression system and method based on solid-state multipass cell post-compression. By real-time detection of the temporal (pulse intensity) and frequency (spectral intensity) characteristics of ultrafast laser pulses propagating in a solid-state multipass cell, a control feedback module is employed to perform cross-module multi-parameter collaborative optimization of the detection information. This allows for precise control of multiple parameters in the energy modulation, spectral broadening, and dispersion compensation modules, balancing the effects of dispersion and nonlinearity on the laser pulse, suppressing spectral modulation, reducing negative chirp and nonlinear phase distortion at the pulse's leading and trailing edges, and improving the quality of pulse compression. By introducing a real-time detection and control feedback module, this invention ensures the controllability and stability of the dispersion compensation process, resulting in a compressed pulse width closer to the theoretical limit, more uniform spectral broadening, and a more concentrated energy distribution. This significantly improves the efficiency and performance of post-processing stages such as frequency doubling and optical parametric amplification. This spectral optimization and pulse compression system and method based on solid-state multipass cell post-compression demonstrates significant potential and advantages in scientific research, industrial processing, and medical applications. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of a spectral optimization and pulse compression system based on solid multi-pass cell post-compression. Figure 2 A device diagram of one embodiment of the system; Figure 3 The control feedback strategy diagram of the system; Figure 4 The examples show the time-frequency domain characteristic transformation of the optical pulse after processing by the multi-pass cell spectral broadening module, and the compressed pulse time-domain profile distribution after dispersion compensation optimization.

[0021] Component numbers in the diagram: 1. Femtosecond laser; 2. Half-wave plate; 3. Polarizing beam splitter; 4. Convex lens; 5. Concave lens; 6, 7, and 8. Plane mirror; 9 and 10. High-reflectivity concave mirror; 11. Positive dispersive medium; 12 and 13. Plane mirror; 14. Convex lens; 15. Concave lens; 16. Beam splitter; 17 and 18. Diffraction grating pair; 19 and 20. Ultrafast pulse measuring instrument; 21. Host computer. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products or devices.

[0024] Figure 1This paper presents a schematic diagram of a spectral optimization and pulse compression system based on solid-state multipass cell compression. The laser output module emits an input laser pulse, which is adjusted by an energy control module. A mode matching module matches the transverse mode of the ultrafast laser pulse with the eigenmode of the multipass cell, ensuring stable pulse propagation within the cell. The laser pulse then enters a spectral broadening module, where it propagates repeatedly through a positive dispersive medium, undergoing nonlinear and dispersion effects, resulting in broadening in both the time and frequency domains. After beam shortening and collimation by an optical path collimation module, the broadened pulse enters a dispersion compensation module for pulse compression. A real-time detection module measures the time-frequency characteristics of the laser pulse, and a control feedback module performs cross-module multi-parameter collaborative optimization of the detection information. This precisely controls the system parameters of the energy control, spectral broadening, and dispersion compensation modules, suppressing spectral modulation, reducing negative chirp and nonlinear phase distortion at the pulse's leading and trailing edges, and improving the quality of pulse compression. This invention brings the output compressed pulse width close to the Fourier limit, reducing pulse width and increasing peak power.

[0025] Specifically, the system includes the following modules: laser output module, energy control module, mode matching module, spectral broadening module, optical path collimation module, dispersion compensation module, real-time detection module, and control feedback module.

[0026] The following combination Figure 2 The functions and structure of each module are explained in detail.

[0027] The laser output module emits an input laser pulse through a femtosecond laser 1. The center wavelength of the pulsed laser is 800 nm, the typical spectral bandwidth is 40 nm, and the pulse width is 60 fs.

[0028] The energy control module consists of a half-wave plate 2 and a polarizing beam splitter 3, both operating at a wavelength of 785 nm. This allows for continuous adjustment of the pulse energy and protects the system and components. When linearly polarized laser light is incident on the half-wave plate, the polarization component parallel to the optical axis passes directly, while the polarization component perpendicular to the optical axis experiences a π-phase delay, thus rotating the polarization direction of the outgoing light relative to the incident light by π. α ,in α This refers to the angle of the half-wave plate. Subsequently, the polarizing beam splitter separates the beam into two orthogonally polarized components, which are adjusted... α This allows for control of the power distribution ratio of the incident laser, achieving an energy adjustment range from 1% to 99%.

[0029] The mode matching module, consisting of a convex lens 4 and a concave lens 5, is used to adjust the transverse mode of the laser beam, ensuring that the input beam matches the eigenmode of the spectral broadening module, thus guaranteeing stable transmission of the laser pulse within the module. The focal length of the convex lens is... f 1. The focal length of the concave lens isf 2, the relationship is: the relationship is: f 2 = -( oh 1 / oh 0) f 1. Lens spacing is l = f 1(1- oh 1 / oh 0), where, oh 0 represents the input beam radius. oh 1 represents the waist radius after pattern matching, and it must satisfy... f 1 oh 1.

[0030] The transmission direction of the laser pulse is adjusted by using plane mirrors 6 and 7 so that it enters the spectral broadening module.

[0031] The spectral broadening module includes a plane mirror 8 and a radius of curvature of... R The system consists of high-reflectivity concave mirrors 9 and 10, a positive dispersive medium 11, and a plane mirror 12. Plane mirrors 8 and 12 control the incident and exit beams. 9 and 10 form a closed cavity, i.e., a multi-pass cell. 11 is placed at the center of the cavity, and the cavity length... L satisfy R < L <2 R The laser pulse, entering the module at an angle, can propagate back and forth, passing through 11 multiple times. During each propagation, the optical pulse undergoes Kerr nonlinearity, resulting in self-phase modulation (SPM), and is simultaneously affected by group velocity dispersion (GVD), causing the pulse to broaden in both the frequency and time domains. This is achieved by adjusting the radius of curvature. R With cavity length L Controlling the number of times the laser pulse travels in the multi-pass cell N The nonlinear phase accumulation and dispersion broadening are affected and should be optimized based on the output spectral bandwidth and the target compression quality.

[0032] The optical path collimation module consists of a plane mirror 13, a convex lens 14, and a concave lens 15. It is located after the spectral broadening module and its function is to reduce the beam after nonlinear broadening and collimate it for output.

[0033] Beam splitter 16 splits the ultrafast laser pulse into two, with one output to the dispersion compensation module and the other output to the real-time detection module.

[0034] The dispersion compensation module consists of a pair of adjustable diffraction gratings 17 and 18. Dispersion compensation for the broadened pulse is achieved by adjusting the diffraction angles and spacing of 17 and 18. The time-domain information of the light pulse is analyzed using an ultrafast pulse measuring instrument 19. By comparing it with the theoretical Fourier transform limit, it is determined whether the compression standard has been met. If the compression standard is not met, the dispersion compensation parameters are recalibrated until the compressed pulse meets the preset indicators. Specifically, through linkage with the real-time detection module, the spacing of the diffraction grating pair is dynamically adjusted according to the dispersion characteristics of the pulse to be compressed. h and beam incident angle i This is done to match the dispersion introduced by the broadening process, thereby ensuring that the output pulse has a time width close to the Fourier limit after compression.

[0035] The real-time detection module includes ultrafast pulse measuring instruments 19 and 20, used to acquire the spectral width, phase information, and temporal waveform characteristics of the broadened pulse in real time, and transmit the detection information to the control feedback module. Both 19 and 20 include a frequency domain analysis system and a time domain analysis system. The frequency domain analysis system uses a high-resolution spectrometer (spectral range: 600–1000 nm, spectral resolution ≤0.1 nm) to obtain the degree of spectral broadening and center wavelength drift. The time domain analysis system uses an FROG (Frequency Resolved Optical Gate) device (measurement accuracy up to ±0.5 fs, phase reconstruction error <0.1 rad) to acquire pulse width and chirp information. The time-frequency characteristics of the ultrafast pulse are detected in real time, and the detection information is transmitted to the control host computer 21.

[0036] The control feedback module, based on the analysis and calculation of the time-frequency information of the ultrafast pulse by the host computer 21, performs cross-module, multi-parameter coordinated control of modules such as energy regulation, spectral broadening, and dispersion compensation. Specific control strategies are as follows: Figure 3 As shown, the input parameter is the rotation angle of the half-wave plate. α radius of curvature of concave mirror R、 cavity length L、 grating pair spacing h、 Grating incident angle I, Input pulse width t laser 、 Input pulse energy E laser 、 Input spectral width Δ l laser 、 Output pulse width t test 、 Output pulse energy E test 、 Output spectral width Δ l test Based on the time-frequency characteristics of the pulse, the real-time pulse width is determined. t test and real-time spectral width Δk test Compared with theoretical pulse width t theory and theoretical spectral width Δ l theory In comparison, if Δ l test Less than Δ l theory If the spectral broadening is small, it is necessary to adjust the rotation angle of the half-wave plate. α To adjust the input energy of the pulse E laser Simultaneously adjust the radius of curvature of the concave mirror in the spectral broadening module. R Cavity length L To improve the nonlinear effect; further, if t test Greater than t theory Then the dispersion compensation is insufficient, according to t test and t theory Calculate dispersion compensation amount β Adjust the spacing of the diffraction grating pairs in the dispersion compensation module. h and the incident angle of the beam of the grating i This ensures that the amount of dispersion compensated by the dispersion compensation module matches the amount of dispersion increased by the spectral broadening module. This is achieved when Δ... l test ≥Δ l theory and t test ≤ t theory Under these two conditions, the compressed pulse approaches the Fourier transform limit, resulting in an ultrafast output pulse.

[0037] Control Feedback Strategy Diagram N Δ l theory , t theory and β The calculation method for the parameters is as follows: (1) (2) (3) (4) Figure 4 The time-frequency domain characteristic transformation of the optical pulse after processing by the multi-pass cell spectral broadening module is shown, as well as the time-domain profile distribution of the compressed pulse after dispersion compensation optimization. Figure 4 (a) and (b) are unoptimized output pulses, which have low spectral cleanliness and obvious base and side lobes in their temporal profile distribution. Figure 4 (c) and (d) are the optimized output pulses, with smooth spectra and pulse temporal profiles without a base and low sidelobe intensity.

[0038] It is obvious to those skilled in the art that the modules or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those described herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A spectral optimization and pulse compression system based on solid multi-pass cell post-compression, characterized in that, include: The system includes a laser output module, an energy control module, a mode matching module, a spectral broadening module, an optical path collimation module, a dispersion compensation module, a real-time detection module, and a control feedback module. The laser output module uses a femtosecond laser to emit input laser pulses; The energy control module is used to adjust the energy of the incident laser pulse generated by the femtosecond laser and transmit it to the mode matching module. The pattern matching module matches the optical pulses to the eigenmodes of the multipass cell; The spectral broadening module, including an optical multipass cell and a positive dispersive medium, adjusts the radius of curvature of the concave mirror. R and cavity length L The optical pulse is controlled to travel back and forth within the multipass cell, so that the optical pulse is subjected to nonlinear and dispersion effects each time it passes through the medium, thereby achieving broadening in the frequency and time domains. The optical path collimation module collimates the broadened optical pulse and outputs it after beam splitting. One path is transmitted to the dispersion compensation module, and the other path is transmitted to the real-time detection module. The dispersion compensation module adjusts the system dispersion, specifically by dynamically adjusting the diffraction grating pair spacing based on the dispersion characteristics of the pulse to be compressed, in conjunction with the real-time detection module. h and beam incident angle θ To match the dispersion introduced by the broadening process, ensuring that the output pulse's time width after compression is close to the Fourier limit; The real-time detection module is used to detect the time-frequency information of the ultrafast pulse before and after entering the dispersion compensation module. Specifically, it acquires the time-frequency characteristics of the light pulse by real-time acquisition of the spectral width, phase information and time waveform characteristics of the broadened pulse, evaluates the time-domain and frequency-domain characteristics of the pulse, and transmits the detection information to the control feedback module. The control feedback module, based on the detection data from the real-time detection module, uses a parameter optimization algorithm to determine whether the current system state meets the preset indicators for pulse compression. It coordinates with modules such as energy regulation, spectral broadening, and dispersion compensation to perform cross-module collaborative optimization and adjustment of system parameters to achieve spectral optimization and pulse compression.

2. The spectral optimization and pulse compression system based on solid multi-pass cell post-compression according to claim 1, characterized in that, The energy regulation module includes: a half-wave plate for adjusting the energy of the incident laser pulse; and a polarizing beam splitter for separating and controlling the power distribution ratio of orthogonal polarization components to achieve precise energy regulation.

3. The spectral optimization and pulse compression system based on solid multi-pass cell post-compression according to claim 1, characterized in that, The mode matching module includes a convex lens and a concave lens with a focal length matching the convex lens, and has beam expanding and contracting functions to ensure that the transverse modes of the ultrafast laser match the eigenmodes of the multipass cell; the focal length of the convex lens is... f 1. The focal length of the concave lens is f 2, their relationship is: f 2 = -( ω 1 / ω 0) f 1. Lens spacing is l = f 1(1- ω 1 / ω 0), where, ω 0 represents the input beam radius. ω 1 represents the waist radius after pattern matching, and it must satisfy... f 1 ω 1.

4. The spectral optimization and pulse compression system based on solid multi-pass cell post-compression according to claim 1, characterized in that, The multipass cell of the spectral broadening module consists of a pair of cells with a radius of curvature of... R A closed cavity formed by two concave mirrors placed opposite each other, the length of the cavity is... L satisfy R < L <2 R； A piece of fused silica with positive dispersion characteristics is placed between two concave mirrors as the positive dispersion medium. The ultrafast laser pulse is transmitted back and forth multiple times in the multipass cell at an inclined angle. Each time it passes through the positive dispersion medium, it is subjected to nonlinearity and dispersion, which broadens the ultrafast laser pulse in the time and frequency domains.

5. The spectral optimization and pulse compression system based on solid multi-pass cell post-compression according to claim 1, characterized in that, The optical path collimation module includes a lens group consisting of a convex lens and a concave lens, used to collimate the ultrafast pulses that have passed through the spectral broadening module.

6. The spectral optimization and pulse compression system based on solid multi-pass cell post-compression according to claim 1, characterized in that, The dispersion compensation module includes a diffraction grating pair, which performs dispersion compensation on the laser pulses output from the solid multipass cell, i.e., time domain compression, to obtain ultrafast lasers with narrower pulse widths and higher peak power.

7. The spectral optimization and pulse compression system based on solid multi-pass cell post-compression according to claim 1, characterized in that, The real-time detection module includes a frequency domain analysis system and a time domain analysis system. The frequency domain analysis system acquires the spectral information of the laser pulse, and the time domain analysis system acquires the time domain intensity information of the laser pulse. By detecting the time-frequency characteristics of the ultrafast pulse in real time, the detection information is transmitted to the control feedback module.

8. The spectral optimization and pulse compression system based on solid multi-pass cell post-compression according to claim 1, characterized in that, The control feedback module is responsible for receiving detection information from the real-time detection module, and adjusting the input energy of the pulse through analysis and calculation by the host computer. E laser The radius of curvature of the concave mirror in the spectral broadening module R Cavity length L And the spacing of the diffraction grating pairs in the dispersion compensation module h and the incident angle of the beam of the grating θ This ensures that the amount of dispersion compensated by the dispersion compensation module matches the amount of dispersion increased by the spectral broadening module, guaranteeing that the output pulse's compressed time width is close to the Fourier limit.

9. The spectral optimization and pulse compression system based on solid multi-pass cell post-compression according to claim 8, characterized in that, The specific control strategy of the control feedback module is as follows: based on the time-frequency characteristics of the pulse, the real-time pulse width is adjusted. τ test and real-time spectral width Δ λ test Compared with theoretical pulse width τ theory and theoretical spectral width Δ λ theory In comparison, if Δ λ test Less than Δ λ theory If the spectral broadening is small, it is necessary to adjust the rotation angle of the half-wave plate. α To adjust the input energy of the pulse E laser Simultaneously adjust the radius of curvature of the concave mirror in the spectral broadening module. R Cavity length L To improve the nonlinear effect; further, if τ test Greater than τ theory Then the dispersion compensation is insufficient, according to τ test and τ theory Calculate dispersion compensation amount β Adjust the spacing of the diffraction grating pairs in the dispersion compensation module. h and the incident angle of the beam of the grating θ This ensures that the amount of dispersion compensated by the dispersion compensation module matches the amount of dispersion increased by the spectral broadening module; while satisfying Δ λ test ≥Δ λ theory and τ test ≤ τ theory Under these two conditions, the compressed pulse approaches the Fourier transform limit, resulting in an ultrafast output pulse.

10. A spectral optimization and pulse compression method based on solid multi-pass cell post-compression, characterized in that, Cross-module collaborative optimization of the system according to any one of claims 1-9, achieving dynamic optimization through energy pre-tuning, broadening control, and compression feedback linkage, and dynamically adjusting system parameters to a preset compression target, includes the following steps: Laser output: The femtosecond laser outputs ultrafast laser pulses; Energy control: The energy of the incident laser pulse generated by the femtosecond laser is adjusted by the energy control module and transmitted to the mode matching module; Mode matching: Adjusting the transverse mode of the laser pulse to match the eigenmode of the multipass cell; Spectral broadening: Adjusting the radius of curvature of the concave mirror R and cavity length L The optical pulse is controlled to travel back and forth within the multipass cell, so that the optical pulse is subjected to nonlinear and dispersion effects each time it passes through the medium, thereby achieving broadening in the frequency and time domains. Optical path collimation: The beam after passing through the spectral broadening module is reduced and collimated for output; Dispersion compensation: Adjust the spacing of the diffraction grating pairs and the incident angle of the beam of the grating to match the amount of dispersion introduced by the broadening process, so as to ensure that the output pulse has a time width close to the Fourier limit after compression. Real-time detection: Real-time acquisition of the spectrum width, phase information and time waveform characteristics of the broadened pulse, and transmission of the detection information to the control feedback module; Control feedback: Based on the detection data from the real-time detection module, determine whether the real-time pulse time-frequency information matches the theoretically calculated spectrum and Fourier transform limit pulse width. If they do not match, optimize the parameters until the output pulse satisfies the Fourier transform limit.

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