Nonlinear pulse compression method and related device based on multi-pass cavity of annular tire surface

Abstract

The present application relates to the technical field of laser pulse compression, and discloses a nonlinear pulse compression method and related device based on an annular tire surface multi-pass cavity. The method comprises: using an annular tire surface multi-pass cavity as the core component of nonlinear pulse compression, the multi-pass cavity adopts a closed annular optical path, and the cavity surface of the annular tire surface multi-pass cavity corresponding to the annular cavity is processed with a tire surface for astigmatism correction; coating the cavity surface of the annular cavity with a low chirp or negative chirp dielectric film or metal film to avoid the introduction of positive chirp or nonlinear chirp during pulse reflection; inserting a solid medium or an inert gas into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity; incidenting the pulse to be compressed into the annular tire surface multi-pass cavity, and changing the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle to adjust the optical path and intensity of the nonlinear effect; and performing dispersion compensation on the pulse that has completed nonlinear spectral broadening through the annular tire surface multi-pass cavity to achieve pulse compression.

Description

Technical Field

[0001] The present application relates to the field of laser pulse compression technology, and in particular to a nonlinear pulse compression method based on a multi-pass cavity on an annular tire surface and a related device. Background Art

[0002] In the field of laser pulse compression, nonlinear pulse compression methods exploit the nonlinear effects of the medium (such as self-phase modulation) to broaden the pulse spectrum and, combined with dispersion compensation, achieve ultrashort pulse output. These methods have important applications in industrial processing, precision measurement, and scientific research. In existing technologies, the Herriott cell, a typical multi-pass cavity structure, is widely used to construct nonlinear pulse compression systems. These cells utilize multiple sets of reflective lenses to create a closed optical path, achieving multiple reflections of the light beam and enhancing the nonlinear effect. However, this solution has significant drawbacks: First, the Herriott cavity relies on precise adjustment of the incident angle and mirror spacing, and optical path alignment requires a three-dimensional adjustment mount, which requires a high level of experience from the optical engineer and significantly increases the complexity and time cost of debugging. Second, the open optical path design is susceptible to environmental vibration and temperature fluctuations. Vibration causes the light beam to deviate from the reflection path, and temperature changes change the cavity size through thermal expansion, resulting in nonlinear instability and optical path mismatch, which seriously affects the repeatability and reliability of pulse compression. Third, the Herriott cavity has strict requirements on the collimation and mode matching of the input beam. The thermal drift of industrial lasers can easily lead to a decrease in cavity efficiency. Moreover, its large size requires external temperature control and pressure stabilization devices, making it difficult to meet the requirements of compact module packaging. These issues make the Herriott cavity unstable and limited in adaptability in practical applications. An improved solution with high stability, easy debugging, and compact structure is urgently needed.

[0003] To address the shortcomings of existing technologies, those skilled in the art have attempted to improve performance by modifying the multi-pass cavity structure. While traditional ring cavities offer a closed optical path, single cylindrical reflections introduce astigmatism, leading to beam distortion, and fail to address the synergistic effects of chirp control and nonlinear effects.

[0004] Therefore, a method is urgently needed to solve at least one of the above problems. Summary of the Invention

[0005] This application provides a nonlinear pulse compression method and related device based on an annular tire tread multi-pass cavity, aiming to address the technical challenges faced by those skilled in the art in attempting to improve performance by modifying the multi-pass cavity structure. While conventional annular cavities possess closed optical path characteristics, single cylindrical reflections introduce astigmatism, leading to beam distortion, and fail to address the synergistic effects of chirp control and nonlinear effect regulation.

[0006] In a first aspect, an embodiment of the present application provides a nonlinear pulse compression method based on a multi-pass cavity on an annular tire surface, comprising:

[0007] An annular tire surface multi-pass cavity is used as the core component of nonlinear pulse compression. The annular tire surface multi-pass cavity adopts a closed annular optical path. The cavity surface of the annular tire surface multi-pass cavity corresponding to the annular cavity is processed with a tire surface to correct astigmatism.

[0008] A low-chirp or negative-chirp dielectric film or metal film is plated on the cavity surface of the annular cavity to avoid the introduction of positive chirp or nonlinear chirp during pulse reflection;

[0009] Inserting a solid medium or an inert gas into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity;

[0010] injecting a pulse to be compressed into the multi-pass cavity of the annular tire surface, and changing the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle to adjust the optical path and intensity of the nonlinear effect;

[0011] Dispersion compensation is performed on pulses that have undergone nonlinear spectral broadening through the annular tire surface multi-pass cavity to achieve pulse compression. The closed annular optical path of the annular tire surface multi-pass cavity reduces optical path detuning caused by vibration or temperature fluctuations, and the closed optical axis characteristic reduces the debugging complexity of optical path alignment. Moreover, under the same optical path, the length of the annular tire surface multi-pass cavity is shorter than that of a traditional Herriott cavity.

[0012] In some embodiments, the step of coating a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the ring cavity includes: designing the film layer structure of the dielectric film or metal film based on the central wavelength, spectral bandwidth, and target chirp compensation amount of the pulse to be compressed, so that the film layer provides low-chirp or negative-chirp reflection characteristics that match the pulse chirp characteristics within the spectral range of the pulse; wherein the chirp amount of the negatively chirped film layer complements the positive chirp introduced by the nonlinear effect in the ring cavity, so as to synchronously compensate for the transmission chirp during the pulse spectrum broadening process, thereby reducing the number of extra-cavity dispersion compensation elements used.

[0013] In some embodiments, a solid medium or an inert gas is inserted into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity, including: when the nonlinear medium is a solid medium, a crystal or glass material with a matching nonlinear coefficient is selected, the size of the solid medium is adapted to the optical path of the annular cavity, and the intensity of the nonlinear effect is regulated by adjusting the material refractive index or doping concentration of the solid medium; when the nonlinear medium is an inert gas, the gas filling pressure of the annular cavity is controlled within the range of 10 kPa to 1 MPa, and the nonlinear coefficient is adjusted by changing the gas type and filling pressure to match the nonlinear spectral broadening requirements of the compressed pulses with different energies and pulse widths.

[0014] In some embodiments, the step of injecting the pulse to be compressed into the annular tire surface multi-pass cavity includes: pre-optimizing the beam quality of the pulse to be compressed to ensure the uniformity of the light field of the incident light beam; utilizing the closed optical axis characteristics of the annular tire surface multi-pass cavity to achieve automatic alignment of the optical path through single-incident calibration, without relying on a three-dimensional adjustment frame for precise angle adjustment, thereby reducing the debugging complexity of the incident end.

[0015] Exemplarily, the adjustment of the incident angle changes the number of reflections of the pulse to be compressed in the cavity to adjust the optical path and intensity of the nonlinear effect, including: establishing a correspondence model between the incident angle and the number of reflections, and dynamically changing the number of reflections of the pulse to be compressed in the multi-pass cavity of the annular tire surface within a preset range by adjusting the incident angle; calculating the required number of reflections through the correspondence model according to the pulse width after compression of the target pulse and the nonlinear spectrum broadening requirements, and matching the corresponding incident angle to linearly tune the optical path and intensity of the nonlinear effect, thereby achieving flexible control of the pulse width.

[0016] In some embodiments, the dispersion compensation is performed on the pulse that has completed nonlinear spectral broadening after passing through the annular tire tread multi-pass cavity to achieve pulse compression, including: using a chirped mirror pair to perform dispersion compensation, and the chirp amount of a single piece of the chirped mirror pair is matched and designed according to the pre-compensated chirp amount of the annular cavity membrane layer and the pulse bandwidth after spectral broadening, wherein the cumulative compensated total dispersion amount offsets the positive dispersion and transmission chirp introduced by the pulse during the nonlinear spectral broadening process; when the negative chirp provided by the annular cavity membrane layer has partially compensated for the pulse chirp, the number of lenses of the chirped mirror pair is reduced, so that the dispersion compensation process only requires 1-2 chirped mirrors to complete the total dispersion compensation, thereby simplifying the dispersion compensation system structure.

[0017] In some embodiments, before performing dispersion compensation on the pulses that have completed nonlinear spectral broadening through the annular tire surface multi-pass cavity, the method further includes: using the tire surface to correct the astigmatism during light beam transmission to improve the output light beam quality; and compensating for chirp during pulse spectral broadening through the low-chirp or negative-chirp dielectric film or metal film to reduce the number of chirped mirrors used outside the cavity.

[0018] In a second aspect, the present application provides a nonlinear pulse compression device based on a multi-pass cavity on an annular tire surface, the device comprising:

[0019] An astigmatism correction unit is used to use an annular tire surface multi-pass cavity as a core component of nonlinear pulse compression, wherein the annular tire surface multi-pass cavity adopts a closed annular optical path, and the cavity surface of the annular tire surface multi-pass cavity corresponding to the annular cavity is processed with a tire surface for astigmatism correction;

[0020] a cavity surface coating unit, used for coating a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the annular cavity to avoid the introduction of positive chirp or nonlinear chirp during pulse reflection;

[0021] a medium insertion unit, used for inserting a solid medium or an inert gas into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity;

[0022] a pulse injection unit, configured to inject a pulse to be compressed into the multi-pass cavity of the annular tire surface, and change the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle, so as to adjust the optical path and intensity of the nonlinear effect;

[0023] A compression implementation unit is used to perform dispersion compensation on pulses that have undergone nonlinear spectral broadening through the annular tire surface multi-pass cavity to achieve pulse compression; wherein the closed annular optical path of the annular tire surface multi-pass cavity reduces optical path detuning caused by vibration or temperature fluctuations, the closed optical axis characteristic reduces the debugging complexity of optical path alignment, and under the same optical path, the length of the annular tire surface multi-pass cavity is shorter than that of a traditional Herriott cavity.

[0024] In a third aspect, an embodiment of the present application provides a control module, which includes a memory and a processor, wherein the memory is used to store a computer program, and the processor is used to execute the computer program and implement the method provided in any embodiment of the present application when executing the computer program.

[0025] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the processor enables the processor to implement the method provided in any embodiment of the present application.

[0026] The present invention provides a nonlinear pulse compression method and related device based on an annular tire-tread multi-pass cavity. This method achieves efficient pulse compression through an innovative cavity structure and control mechanism. Specifically, the annular tire-tread multi-pass cavity features a closed annular optical path, unlike the open optical path of a traditional Herriott cavity, forming a closed path for the circulatory propagation of the light beam. Tread processing, by machining the surface of the annular cavity with a tire-tread structure, corrects astigmatism during beam propagation and improves output beam quality. A chirped film layer, coated with a low-chirp or negative-chirp dielectric / metal film on the cavity surface, prevents positive chirp or nonlinear chirp introduced by reflection and simultaneously compensates for the chirp effect in pulse spectral broadening. A solid medium (such as a nonlinear crystal) or an inert gas is inserted into the cavity. The nonlinear coefficient is adjusted by material properties (refractive index, doping concentration) or gas parameters (type, pressure), enhancing the efficiency of nonlinear spectral broadening. By adjusting the incident angle, the number of pulse reflections within the cavity is dynamically varied (from 4 to 16 passes), linearly adjusting the optical path and intensity of the nonlinear effect, and achieving flexible control of pulse width. The closed optical axis simplifies optical alignment and reduces debugging complexity. The cavity length is only one-quarter that of a Herriott cavity for the same optical path, enabling compact packaging. Combined with film-layer chirp compensation, the number of extracavity dispersion components (such as chirped mirrors) is reduced. The pulse to be compressed is pre-optimized (beam quality M² ≤ 1.1) before injection, undergoing nonlinear spectral broadening in the ring cavity. Dispersion is then compensated by the chirped mirror pair, ultimately achieving pulse compression.

[0027] The provided method has at least the following beneficial effects:

[0028] Solve the problem of difficult debugging: The closed optical axis feature supports single-incident automatic alignment, eliminating the need for a three-dimensional adjustment frame to precisely adjust the incident angle and mirror spacing, significantly reducing reliance on engineer experience and shortening debugging time.

[0029] Improved long-term working stability: The closed ring optical path isolates external vibration interference and prevents the light beam from deviating from the reflection path; the cavity structure is less affected by temperature fluctuations (no thermal expansion and optical path mismatch in the open optical path), the stability of nonlinear effects (such as self-phase modulation) is greatly improved, and the output pulse width fluctuation is significantly reduced.

[0030] Compact modular packaging: The cavity length is only 1 / 4 of that of a Herriott cavity at the same optical path length, eliminating the need for external temperature control or pressure stabilization devices. This facilitates integrated design and meets industrial requirements for miniaturized, high-reliability modules.

[0031] Optimizing beam quality and compression efficiency: The tire tread structure corrects astigmatism, avoiding beam distortion caused by single cylindrical reflection in traditional annular cavities. The negatively chirped film layer synchronously compensates for chirp introduced by reflection, reducing the number of extra-cavity dispersion compensation components, simplifying the system structure while improving phase consistency. The compressed pulse spectrum broadening uniformity and beam quality (M² factor) are significantly optimized.

[0032] Enhanced flexibility in tuning nonlinear effects: Dynamically adjust the number of reflections (4-16 passes) based on the incident angle. Combined with parameter control of solid / gas nonlinear media (such as gas pressure 10kPa-1MPa), it can linearly match input pulses of different energies and pulse widths, achieve precise control of nonlinear effect intensity, and support wide-range tuning of pulse width.

[0033] Lowering the threshold for industrial applications: The requirements for input beam mode matching are reduced (no strict collimation is required), compatibility with mode changes caused by thermal drift of industrial lasers, and stable cavity efficiency; the coordinated design of chirped film layers and chirped mirror pairs reduces the complexity of the dispersion compensation module and improves system robustness.

[0034] In summary, the present invention breaks through the bottlenecks of traditional Herriott cavity in debugging difficulty, environmental stability and volume through the systematic innovation of "closed ring optical path + tire surface astigmatism correction + chirped film layer compensation + nonlinear medium tuning", and provides a compression solution for high-power ultrashort pulse laser systems that combines high performance, easy integration and high adaptability. It is particularly suitable for industrial processing and scientific research scenarios with strict requirements on stability and compactness.

[0035] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0037] Figure 1 This is a schematic flow chart of the steps of a nonlinear pulse compression method based on a multi-pass cavity on an annular tire surface provided by an embodiment of the present application;

[0038] Figure 2 This is a schematic diagram of the first structure of an annular cavity provided in one embodiment of the present application;

[0039] Figure 3 This is a schematic diagram of the second structure of an annular cavity provided in one embodiment of the present application;

[0040] Figure 4 This is a schematic diagram of the third structure of an annular cavity provided in one embodiment of the present application;

[0041] Figure 5 This is a schematic diagram of the fourth structure of an annular cavity provided in one embodiment of the present application;

[0042] Figure 6 This is a fifth structural diagram of an annular cavity provided in one embodiment of the present application;

[0043] Figure 7 This is a sixth structural diagram of an annular cavity provided in one embodiment of the present application;

[0044] Figure 8 This is a schematic diagram of the pulse compression effect provided by an embodiment of the present application;

[0045] Figure 9 1 is a schematic diagram of the characterization results of a compressed pulse provided by an embodiment of the present application;

[0046] Figure 10 This is a schematic block diagram of the structure of a nonlinear pulse compression device based on a multi-pass cavity on an annular tire surface provided by an embodiment of the present application;

[0047] Figure 11 This is a schematic block diagram of the structure of a control module provided in one embodiment of the present application.

[0048] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0050] The flowcharts shown in the accompanying drawings are for illustrative purposes only and do not necessarily include all contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may be decomposed, combined, or partially merged, so the actual execution order may vary depending on the actual situation.

[0051] It should be understood that, in order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, terms such as "first" and "second" are used to distinguish between identical or similar items having substantially the same functions and effects. Those skilled in the art will understand that terms such as "first" and "second" do not limit the quantity or order of execution, and that terms such as "first" and "second" do not necessarily define differences.

[0052] It should be understood that the terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0053] It will also be understood that the term "and / or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0054] The following describes some embodiments of the present application in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0055] In the field of laser pulse compression, nonlinear pulse compression methods exploit the nonlinear effects of the medium (such as self-phase modulation) to broaden the pulse spectrum and, combined with dispersion compensation, achieve ultrashort pulse output. These methods have important applications in industrial processing, precision measurement, and scientific research. In existing technologies, the Herriott cell, a typical multi-pass cavity structure, is widely used to construct nonlinear pulse compression systems. These cells utilize multiple sets of reflective lenses to create a closed optical path, achieving multiple reflections of the light beam and enhancing the nonlinear effect. However, this solution has significant drawbacks: First, the Herriott cavity relies on precise adjustment of the incident angle and mirror spacing, and optical path alignment requires a three-dimensional adjustment mount, which requires a high level of experience from the optical engineer and significantly increases the complexity and time cost of debugging. Second, the open optical path design is susceptible to environmental vibration and temperature fluctuations. Vibration causes the light beam to deviate from the reflection path, and temperature changes change the cavity size through thermal expansion, resulting in nonlinear instability and optical path mismatch, which seriously affects the repeatability and reliability of pulse compression. Third, the Herriott cavity has strict requirements on the collimation and mode matching of the input beam. The thermal drift of industrial lasers can easily lead to a decrease in cavity efficiency. Moreover, its large size requires external temperature control and pressure stabilization devices, making it difficult to meet the requirements of compact module packaging. These issues make the Herriott cavity unstable and limited in adaptability in practical applications. An improved solution with high stability, easy debugging, and compact structure is urgently needed.

[0056] To address the shortcomings of existing technologies, those skilled in the art have attempted to improve performance by modifying the multi-pass cavity structure. While traditional ring cavities offer a closed optical path, single cylindrical reflections introduce astigmatism, leading to beam distortion, and fail to address the synergistic effects of chirp control and nonlinear effects.

[0057] Therefore, a method is urgently needed to solve at least one of the above problems.

[0058] To resolve the above, please refer to Figures 1 to 7(exist Figure 2-7 In the figure, 1 is an annular cavity, 2 is a chirped mirror, 3 is a nonlinear medium, 3.1 is a solid nonlinear medium, 3.2 is a gas nonlinear medium, and 4 is a tire surface after astigmatism correction. The present embodiment provides a nonlinear pulse compression method based on an annular tire surface multi-pass cavity, which is applied to a control module. Specifically, as Figure 1 As shown, the nonlinear pulse compression method based on the annular tire surface multi-pass cavity includes steps S101 to S105. The details are as follows:

[0059] Step S101. Use an annular tire surface multi-pass cavity as a core component of nonlinear pulse compression, wherein the annular tire surface multi-pass cavity adopts a closed annular optical path, and the cavity surface of the annular tire surface multi-pass cavity corresponding to the annular cavity is processed with a tire surface for astigmatism correction.

[0060] Specifically, a torus-shaped multi-pass cavity with a closed annular optical path is used as the core component for nonlinear pulse compression. The cavity (reflection surface) of the torus cavity is machined with a torus surface structure to correct astigmatism generated by the beam's multiple reflections. The torus surface is an aspheric surface with different radii of curvature in two orthogonal directions, which can compensate for the astigmatic distortion caused by single cylindrical reflections in traditional torus cavities.

[0061] The annular cavity utilizes a closed annular optical path, with multiple reflectors forming a closed path (e.g., a circular, elliptical, or polygonal closed loop). The light beam propagates within the cavity along the closed optical axis. A tread structure is precisely machined on the reflector surface (single or multiple cylinders) of the annular cavity. Optimizing the surface parameters using optical design software (e.g., Zemax) effectively corrects astigmatism (e.g., coma and field curvature) during reflection. The reflector substrate can be made of low-thermal expansion materials such as fused quartz, silicon, or metals (e.g., aluminum) to ensure surface stability over long-term use.

[0062] The use of a single cylindrical reflector in a traditional annular cavity causes spot distortion due to astigmatism after multiple reflections, affecting the beam quality of the compressed pulse. The tire tread structure compensates for astigmatism in orthogonal directions through aspheric surfaces, ensuring that the beam maintains high uniformity and collimation after multiple reflections within the cavity. Unlike the open optical path of a Herriott cavity, the closed optical path structure of the annular cavity reduces interference from external vibrations and airflow on the alignment of the optical path, significantly reducing the risk of optical path misalignment. The closed optical axis characteristic makes the propagation path of the light beam within the cavity symmetrical, eliminating the need for precise angle calibration using a three-dimensional adjustment mount, and significantly reducing the debugging complexity compared to the Herriott cavity.

[0063] Step S102: A low-chirp or negative-chirp dielectric film or metal film is plated on the cavity surface of the ring cavity to avoid positive chirp or nonlinear chirp introduced during pulse reflection.

[0064] Specifically, by coating a low-chirp dielectric film or metal film, or a negative-chirp dielectric film or metal film on the surface of the ring cavity's reflector, the chirp introduced during pulse reflection (i.e., the time delay difference between different frequency components of the pulse) is offset by the dispersion characteristics of the film layer, thereby avoiding the interference of positive chirp or nonlinear chirp on subsequent pulse compression.

[0065] Based on the pulse's central wavelength (e.g., 1030 nm) and spectral range (e.g., 1010–1045 nm), multilayer dielectric films (e.g., SiO2 / TiO2 combinations) or metal films (e.g., gold-plated films) are deposited using ion beam sputtering or electron beam evaporation techniques. By optimizing the film thickness and material refractive index, the target chirp (e.g., negative chirp to compensate for dispersion during reflection) is achieved. To address the cumulative effect of multiple pulse reflections within the cavity, the group delay dispersion (GDD) parameters of the film are designed so that the chirp introduced by a single reflection is negative or close to zero, ensuring that the total chirp after multiple reflections is controllable.

[0066] Traditional Herriot cavities fail to control reflection chirp, which introduces phase distortion during pulse spectral broadening and compromises compression efficiency. This step, through dispersion compensation in the film layer, prevents the accumulation of positive chirp or nonlinear chirp, ensuring pulse phase coherence. The negatively chirped film layer partially compensates for intracavity dispersion, reducing the number of chirped mirrors required for subsequent dispersion compensation, simplifying the system architecture and reducing costs.

[0067] Step S103: inserting a solid medium or an inert gas into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity.

[0068] Specifically, a solid medium (such as Yb:YAG crystal, fused quartz) or an inert gas (such as argon, krypton) is inserted into the annular multi-pass cavity as a nonlinear medium. The pulse spectrum broadening is enhanced through the nonlinear optical effect of the medium (such as self-phase modulation), and the intensity of the nonlinear effect is adjusted by the medium type and filling parameters.

[0069] Solid media can be used to fix bulk nonlinear crystals (such as β-BBO and Yb:YAG) or undoped transparent solids (such as fused silica) within a cavity, leveraging their high nonlinear coefficients (e.g., γ value) to achieve strong nonlinear effects, making them suitable for high-energy pulse compression. Gas media can be used to construct a sealed chamber within the cavity, filled with an inert gas (such as argon) and regulated at a pressure of, for example, 1–10 atm. The gas's low damage threshold and adjustable nonlinear coefficient make it suitable for low-energy, high-repetition-rate pulse scenarios. The dielectric layout can place the nonlinear medium at the cavity's optical waist (where the beam radius is minimum) to maximize the efficiency of the nonlinear effect. Solid media can be maintained at a constant temperature using a temperature control device, while gas media can be monitored and regulated in real time using a pressure sensor.

[0070] Unlike Herriott cavities, which rely on a fixed optical path length to control nonlinear effects, this step dynamically tunes the nonlinear coefficient (γ) by changing the dielectric type (solid / gas) or adjusting the gas pressure and solid temperature, adapting to the compression requirements of varying input pulse parameters (energy, pulse width). Solid dielectrics are suitable for high-power applications, while gas dielectrics are suitable for low-damage applications, broadening the application range of compression methods (such as industrial processing and precision measurement).

[0071] Step S104: injecting the pulse to be compressed into the multi-pass cavity of the annular tire surface, and changing the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle to adjust the optical path and intensity of the nonlinear effect.

[0072] Specifically, by injecting the pulse to be compressed into the multi-pass cavity of the annular tire surface at a specific angle, and adjusting the incident angle to change the number of reflections of the pulse in the cavity, the optical path of the nonlinear effect (that is, the total distance the light beam propagates in the nonlinear medium) is controlled, thereby achieving flexible adjustment of the intensity of the nonlinear effect.

[0073] The incident angle adjustment mechanism utilizes a two-dimensional precision turntable (e.g., a motorized stage with an accuracy of ±0.01°) at the cavity input, dynamically adjusting the angle θ between the incident beam and the cavity surface via a servo system. The number of reflections is related to the optical path length: Based on the geometric parameters of the annular cavity (e.g., radius R and cavity surface curvature radius r), a mathematical model is established that relates the incident angle θ to the number of reflections N (e.g., N ∝ 1 / θ, based on the law of reflection in geometric optics). By controlling θ, N can be quantitatively adjusted (e.g., for 8-pass and 12-pass reflections).

[0074] Compared to the Herriott cavity's limitation of a fixed number of reflections, this step achieves continuously adjustable optical path length through angle adjustment, thereby linearly controlling the pulse spectral broadening (Δλ ∝ optical path length × nonlinear coefficient), facilitating on-demand output of compressed pulses with varying pulse widths (e.g., from hundreds of femtoseconds to sub-picoseconds). The closed loop optical path requires less collimation of the input beam than a Herriott cavity, significantly reducing the impact of mode changes caused by thermal drift in industrial lasers on cavity efficiency and improving the system's robustness in complex environments.

[0075] Step S105. Dispersion compensation is performed on the pulses that have undergone nonlinear spectral broadening through the annular tire surface multi-pass cavity to achieve pulse compression; wherein, the closed annular optical path of the annular tire surface multi-pass cavity reduces optical path detuning caused by vibration or temperature fluctuations, the closed optical axis characteristic reduces the debugging complexity of optical path alignment, and under the same optical path, the length of the annular tire surface multi-pass cavity is shorter than that of a traditional Herriott cavity.

[0076] Specifically, after the pulses undergo nonlinear spectral broadening through the ring cavity, group velocity dispersion (GVD) is compensated using a chirped mirror pair or other dispersion compensation device, eliminating the time delay of the different frequency components of the pulse and achieving ultrashort pulse output. The negatively chirped film layer of the ring cavity can pre-compensate for some dispersion, reducing the amount of external compensation.

[0077] The chirped mirror configuration utilizes two or more chirped mirrors (such as the mirrors with negatively chirped films described in step S102) to form a mirror pair. The chirp of a single mirror is designed to be -1000 fs² at 1030 nm. The total dispersion compensation is accumulated through multiple reflections (e.g., eight reflections achieve a total chirp compensation of -8000 fs²). Based on the pulse spectrum's broadened bandwidth (e.g., 1010–1045 nm) and the accumulated intracavity dispersion (including nonlinear chirp and film dispersion), the compensation strategy is optimized using Fourier transforms or numerical simulations to ensure effective correction of second-order and higher-order dispersion.

[0078] Combining pre-compensation with a negatively chirped film layer within the cavity and secondary compensation with an extracavity chirped mirror pair enables phase-matched compression of spectrally broadened pulses. Compared to Herriott cavity solutions, compression efficiency is improved by over 30% (for example, compressing an initial pulse width of 700 fs to sub-hundreds of femtoseconds). The closed optical path of the ring cavity is only one-fourth the length of a Herriott cavity at the same optical path length. Combined with the reduced number of external chirped mirrors, the overall system volume is reduced by over 50%, meeting the compactness requirements of industrial module packaging. The closed optical path structure reduces the impact of temperature fluctuations on the optical path (no external temperature control device is required), significantly reducing the risk of optical path detuning due to vibration interference, and reducing the output pulse width fluctuation from ±15% in traditional solutions to within ±5%.

[0079] In summary, this method systematically solves the inherent defects of the Herriott cavity, such as complex debugging, environmental sensitivity, and large size, through three core technologies: innovative multi-pass cavity structure of the annular tire surface (to solve astigmatism and optical path stability), coordinated regulation of chirped film layers and nonlinear media (to optimize phase matching and nonlinear effects), and dynamic tuning of the number of reflections at the incident angle (flexible control of compression parameters). This provides a breakthrough solution for industrial-grade high-stability pulse compression equipment, with significant technological progress and practical value.

[0080] In some embodiments, the step of coating a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the ring cavity includes: designing the film layer structure of the dielectric film or metal film based on the central wavelength, spectral bandwidth, and target chirp compensation amount of the pulse to be compressed, so that the film layer provides low-chirp or negative-chirp reflection characteristics that match the pulse chirp characteristics within the spectral range of the pulse; wherein the chirp amount of the negatively chirped film layer complements the positive chirp introduced by the nonlinear effect in the ring cavity, so as to synchronously compensate for the transmission chirp during the pulse spectrum broadening process, thereby reducing the number of extra-cavity dispersion compensation elements used.

[0081] The film design parameters are input based on the central wavelength of the pulse to be compressed (e.g. 1030 nm), the spectral bandwidth (e.g. 1010–1045 nm after broadening), and the target chirp compensation amount (e.g. single-pass reflection requires -500 fs 2 Chirp amount), and use thin film design software (such as TFCalc) to establish a multilayer film model.

[0082] For dielectric films, high-refractive-index materials (TiO2, n≈2.3) and low-refractive-index materials (SiO2, n≈1.46) are alternately deposited, and the group delay dispersion (GDD) of different wavelengths is controlled by adjusting the thickness of each layer (with an accuracy of nanometers); for metal films, gold-plated films are selected and a dielectric protective layer is evaporated on the surface to optimize the chirp characteristics in the ultraviolet to near-infrared bands.

[0083] The chirp-complementing strategy involves analyzing the positive dispersion (where the high-frequency component of the pulse lags behind the low-frequency component) introduced by nonlinear effects such as self-phase modulation, and designing the single-reflection chirp of the negatively chirped film (e.g., -1000 fs²@1030 nm) so that it algebraically cancels out the nonlinear positive dispersion within the cavity after multiple reflections (e.g., the accumulated negative chirp over eight reflections is -8000 fs², which offsets the nonlinear positive dispersion by +6000 fs², leaving the remaining -2000 fs² compensated by the extracavity chirped mirror).

[0084] The film is deposited using ion beam sputtering (IBS) technology, and the thickness is monitored by a quartz crystal oscillator to ensure that the film uniformity error is <1%. After coating, a spectrometer (such as the Agilent Cary 5000) and a GDD meter (such as the Femtolasers SPIDER) are used to calibrate the reflectivity (>99.8%) and chirp (error <5%).

[0085] By quantitatively matching the film parameters with nonlinear effects, the phase distortion caused by uncontrolled reflection chirp in traditional Herriot cavities is avoided, ensuring simultaneous "broadening and chirp compensation" during pulse spectral broadening. This ensures that the time-bandwidth product of the compressed pulse approaches the conversion limit (increasing to over 95% of the theoretical value). The negatively chirped film pre-compensates for some dispersion, reducing the number of mirrors in the extracavity chirped mirror pair from four in traditional solutions to two or even one, simplifying optical path debugging and device costs while reducing vibration-sensitive points introduced by external components. The film's wide-spectrum high reflectivity (e.g., reflectivity >99.5% from 1010–1045 nm) accommodates the wavelength drift (±5 nm) of industrial lasers, preventing compression efficiency degradation due to mode mismatch. This improves output pulse energy stability from ±8% in traditional solutions to ±3%.

[0086] In some embodiments, a solid medium or an inert gas is inserted into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity, including: when the nonlinear medium is a solid medium, a crystal or glass material with a matching nonlinear coefficient is selected, the size of the solid medium is adapted to the optical path of the annular cavity, and the intensity of the nonlinear effect is regulated by adjusting the material refractive index or doping concentration of the solid medium; when the nonlinear medium is an inert gas, the gas filling pressure of the annular cavity is controlled within the range of 10 kPa to 1 MPa, and the nonlinear coefficient is adjusted by changing the gas type and filling pressure to match the nonlinear spectral broadening requirements of the compressed pulses with different energies and pulse widths.

[0087] Solid medium implementation methods include: Material selection and adaptation: Select crystals with a higher nonlinear coefficient γ (such as β-BBO, γ≈5×10⁻²³ m² / W) or glass (such as tellurite glass, γ≈2×10⁻² 0 m² / W). Design the dielectric dimensions (e.g., 10 mm diameter, 20 mm length) based on the ring cavity optical path radius (e.g., 50 mm) to ensure the dielectric completely covers the optical waist (beam radius <500 μm). Modulating the material's refractive index through doping concentration (e.g., Yb³⁺ ion concentration 0.1%–1%) or temperature control (accuracy ±0.1°C) allows for adjustment of the nonlinear interaction strength (Δγ / γ ≤ 10%).

[0088] Fixation and temperature control are achieved by using a low thermal expansion coefficient bracket (such as Invar) to fix the solid medium, wrapping the semiconductor cooling sheet around it, and maintaining the medium temperature stable through a PID controller to avoid beam distortion caused by thermal lens effect.

[0089] Inert gas medium implementation includes: Gas chamber construction and control: Integrate a sealed gas chamber (volume 100–500 cm 3 ), equipped with a pressure sensor (accuracy ±0.1% FS) and a gas pressure regulator, supporting a pressure range of 10 kPa (low pressure) to 1 MPa (high pressure). Optional gases include argon (low damage threshold, suitable for low-energy pulses) and krypton (high nonlinear coefficient, suitable for high-energy pulses), and a mass flow controller (accuracy ±0.5%) enables rapid switching between gas types.

[0090] Nonlinear coefficient tuning involves using the nonlinear coefficient γ∝ gas density (γ=γ0×P / P0, where P0 is standard atmospheric pressure) to linearly control the γ value by adjusting the gas pressure (e.g., γ=0.1γ0 at 10 kPa, γ=10γ0 at 1 MPa), to match the broadening requirements of pulses of different energies (e.g., 1 mJ pulse corresponds to 0.5 MPa argon, 0.1 mJ pulse corresponds to 50 kPa argon). Solid media are suitable for high-energy (>1 mJ) and narrow-pulse-width (>500 fs) pulse compression to avoid ionization damage to the gas medium; gas media are suitable for low-energy (<100 μJ) and high-repetition-rate (>100 kHz) scenarios to solve the heat accumulation problem of solid media, allowing the compression method to cover the needs of multiple fields such as industrial processing (high energy) and scientific research measurement (low noise). By continuously adjusting the solid medium doping concentration / temperature or gas pressure, a 10-fold dynamic range of nonlinear interaction intensity (γ=1×10 -23 to 1×10 -22 m 2 / W), compared with the limitations of the fixed nonlinear coefficient of the Herriot cavity, the compression parameters can be quickly optimized for different laser output characteristics (such as fiber laser vs. solid laser), and the compression efficiency can be improved by 20%–50%. The temperature control design of the solid medium suppresses the change of optical path caused by thermal expansion (ΔL / L<10 -6 / ℃), the sealed gas chamber of the gas medium prevents the influence of external pollution (such as dust) on the nonlinear effect, and the system's trouble-free operation time is increased from 500 hours in the traditional solution to more than 2000 hours.

[0091] In some embodiments, the step of injecting the pulse to be compressed into the annular tire surface multi-pass cavity includes: pre-optimizing the beam quality of the pulse to be compressed to ensure the uniformity of the light field of the incident light beam; utilizing the closed optical axis characteristics of the annular tire surface multi-pass cavity to achieve automatic alignment of the optical path through single-incident calibration, without relying on a three-dimensional adjustment frame for precise angle adjustment, thereby reducing the debugging complexity of the incident end.

[0092] The beam quality is pre-optimized by integrating a beam shaping system at the laser output end, including a beam expander (magnification 2–5 times) and a mode filter (such as a single-mode fiber or a spatial filter) to reduce the M of the incident beam to 2 The factor is optimized to <1.1 (close to the diffraction limit), and the spot ellipticity is monitored in real time by a CCD beam profiler (axial ratio <1.2) to ensure light field uniformity.

[0093] Automatic alignment of the closed optical axis utilizes the geometric symmetry of the annular cavity (e.g., the circular cavity optical axis coincides with the cavity central axis) to design a fixed-angle bracket at the incident end (accuracy ±0.1°). This requires only a single incident calibration: the energy at the cavity output is monitored by a photodetector, and the incident angle is fine-tuned to the maximum energy (automatically locking the optimal incident angle). This eliminates the need for the three-dimensional adjustment bracket (X / Y / Z axis ±5° adjustment) and long-term experience-based debugging required by traditional Herriott cavities.

[0094] Traditional Herriott cavities require optical engineers to adjust the three-dimensional angles with micrometer-level precision, a time-consuming process. This embodiment, through closed optical axis features and automatic energy feedback alignment, reduces commissioning time to less than 10 minutes. This approach requires no specialized expertise, significantly reducing labor costs and making it suitable for batch calibration on industrial production lines. Thermal drift in industrial lasers (e.g., a 10°C temperature change can cause a beam pointing drift of ±5 mrad) has far less impact on a ring cavity than a Herriott cavity. The angular tolerance of a closed optical path (±2°) is 20 times that of an open optical path (±0.1°). Even if the beam pointing drifts, the nonlinear effect efficiency is maintained through the remaining number of reflections, reducing the cavity efficiency drop from 40% in traditional solutions to <10%. 2 An incident light beam with a factor of <1.1 ensures that the light spot distortion rate is less than 5% after reflection from the tire surface, avoiding local over-strength / weakness of nonlinear effects caused by uneven light fields and improving the spatiotemporal quality of the compressed pulse (the proportion of time-domain sidelobe energy is less than 5%).

[0095] Exemplarily, the adjustment of the incident angle changes the number of reflections of the pulse to be compressed in the cavity to adjust the optical path and intensity of the nonlinear effect, including: establishing a correspondence model between the incident angle and the number of reflections, and dynamically changing the number of reflections of the pulse to be compressed in the multi-pass cavity of the annular tire surface within a preset range by adjusting the incident angle; calculating the required number of reflections through the correspondence model according to the pulse width after compression of the target pulse and the nonlinear spectrum broadening requirements, and matching the corresponding incident angle to linearly tune the optical path and intensity of the nonlinear effect, thereby achieving flexible control of the pulse width.

[0096] The mathematical model is established based on geometric optics, establishing a relationship between the incident angle θ and the number of reflections N for a ring cavity (radius R): N = 2πR / d*sinθ. Here, d is the arc length interval between adjacent reflection points (a fixed value), and θ is the angle between the incident beam and the tangent line of the cavity surface (0° < θ < 90°). The model is calibrated using optical simulation software (such as LightTools) to ensure a calculated error of <1% for N.

[0097] A motorized rotation stage (0.001° resolution) is installed at the incident end. This stage, connected to a control system, reads the target pulse width in real time (e.g., compressing from 500 fs to 100 fs requires N = 8 passes). This inverse calculation determines θ = 15°, which then drives the stage for automatic positioning. The number of reflections is continuously adjustable from 4 to 16 passes, corresponding to dynamic changes in the nonlinear optical path length from 0.5 m to 2 m.

[0098] By adjusting the angle, quantitative control of the number of reflections N is achieved, enabling linear tuning of the nonlinear optical path length (L = N × l, where l is the optical path length of a single reflection) to maintain spectral broadening Δλ ∝ L × γ (γ is the nonlinear coefficient). This ultimately allows precise control of the compressed pulse width τ ∝ 1 / Δλ (e.g., a target pulse width of 100 fs corresponds to Δλ = 35 nm, and a target pulse width of 200 fs corresponds to Δλ = 17 nm), with a tuning accuracy of ±5 fs. While traditional Herriott cavities require manual replacement of lens groups (a process that takes >30 minutes), this embodiment utilizes a motorized rotary stage to achieve instantaneous switching of the number of reflections, adapting to multi-tasking scenarios (e.g., alternating material cutting and surface treatment processes on the same machine, each requiring different pulse widths) and increasing production efficiency by more than threefold. The wide incident angle adjustment range allows for a certain divergence angle of the incident beam (e.g., ±1 mrad), reducing the precision requirements of the laser collimation system (the collimator focal length can be relaxed from 500 mm in traditional solutions to 200 mm), further reducing hardware costs.

[0099] In some embodiments, the dispersion compensation is performed on the pulse that has completed nonlinear spectral broadening after passing through the annular tire tread multi-pass cavity to achieve pulse compression, including: using a chirped mirror pair to perform dispersion compensation, and the chirp amount of a single piece of the chirped mirror pair is matched and designed according to the pre-compensated chirp amount of the annular cavity membrane layer and the pulse bandwidth after spectral broadening, wherein the cumulative compensated total dispersion amount offsets the positive dispersion and transmission chirp introduced by the pulse during the nonlinear spectral broadening process; when the negative chirp provided by the annular cavity membrane layer has partially compensated for the pulse chirp, the number of lenses of the chirped mirror pair is reduced, so that the dispersion compensation process only requires 1-2 chirped mirrors to complete the total dispersion compensation, thereby simplifying the dispersion compensation system structure.

[0100] According to the pre-compensated chirp of the ring cavity membrane layer (such as single-pass - 1000 fs 2 , 8-pass cumulative - 8000 fs 2 ) and the pulse bandwidth after spectral broadening (Δλ = 35 nm), the required extracavity compensation is calculated as follows: total compensation = −(nonlinear positive dispersion + transmission chirp) + film precompensation; for example, if the nonlinear process introduces +6000 fs 2 , transmission chirp +2000 fs 2 , film compensation -8000 fs 2, then the total compensation amount = 0, and only one chirped mirror is needed for fine-tuning (±500 fs 2 ).

[0101] When the negative chirp of the film has compensated most of the dispersion (e.g. >70%), 1-2 chirped mirrors are used to form a mirror pair (the traditional solution requires 4), and each mirror is designed to have high reflectivity (>99.8%) and low high-order dispersion (third-order dispersion <10 4 fs 3 ), the residual dispersion is compensated by a single or double reflection, simplifying the number of optical path folds (from 4 to 1). By combining intracavity pre-compensation with extracavity fine-tuning, the total dispersion compensation accuracy is improved from ±1000 fs² of traditional solutions to ±200 fs. 2 , ensuring that the temporal sidelobes of the compressed pulse are effectively suppressed (main lobe energy accounts for >95%), avoiding the side lobe energy's adverse effects on material processing (such as the expansion of the heat-affected zone). The reduction in the number of chirped mirrors and the number of optical path folds reduces the volume of the entire compression module from the traditional Herriott cavity solution's 400×300×200mm to 3 Reduced to 200×150×100 mm 3 , suitable for miniaturized equipment (such as portable LiDAR and integrated processing heads). Reducing the number of chirped mirrors directly reduces device costs (a single lens costs about 20,000 yuan, and reducing the number of chirped mirrors by two saves 40,000 yuan). It also reduces the number of reflections, lowers optical loss (from 8% to below 3%), and avoids the cumulative errors introduced by multiple lenses (such as uneven dispersion compensation caused by lens installation angle deviation).

[0102] In some embodiments, before performing dispersion compensation on the pulses that have completed nonlinear spectral broadening through the annular tire surface multi-pass cavity, the method further includes: using the tire surface to correct the astigmatism during light beam transmission to improve the output light beam quality; and compensating for chirp during pulse spectral broadening through the low-chirp or negative-chirp dielectric film or metal film to reduce the number of chirped mirrors used outside the cavity.

[0103] Use aspheric surface design software (such as Code V) to optimize the tire tread parameters so that the curvature radii of the surface in the X / Y directions are R1 and R2, respectively (e.g., R1 = 100 mm, R2 = 200 mm), meeting the astigmatism correction condition: Δ astigmatism Δ astigmatism = 1 / 2R1 - 1 / 2R2 = 0. Use diamond turning or magnetorheological polishing technology to process the surface with a surface accuracy of λ / 10 (λ = 632.8 nm), ensuring that the astigmatism difference of the light beam after 8 reflections is less than λ / 4.

[0104] During the spectrum broadening stage, the symmetry of the pulse spectrum is monitored in real time by a spectrometer. If a leading low-frequency component (positive chirp) is detected, the film chirp is automatically calibrated (for example, from -1000 fs² to -1200 fs²) to ensure that the phase linearity of the broadened spectrum is >98% (Fourier transform phase fluctuation <π / 8).

[0105] The astigmatism caused by single cylindrical reflection in traditional annular cavities deteriorates the spot ellipticity from 1.0 to 1.5. In this embodiment, the ellipticity is maintained below 1.1 after tire tread correction, and the focused spot diameter is reduced from 20 μm to 15 μm, improving the positioning accuracy of precision machining (such as micron-level drilling). Astigmatism correction avoids local dispersion differences caused by beam distortion (the dispersion difference between the edge beam and the center beam in traditional solutions can reach 2000 fs). 2 ), the extracavity chirped mirror only needs to compensate for global dispersion, eliminating the need for complex local compensation designs, reducing algorithm complexity by over 50%. Pre-chirp compensation and astigmatism correction form a closed-loop "broadening-correction-compensation" control system. Compared to the open-loop tuning of the Herriott cavity, the system's robustness to environmental perturbations (such as ±5°C temperature fluctuations and ±10 mrad vibrations) is improved by 70%. The fluctuation of pulse parameters during long-term operation (24 hours) is reduced from ±15% to ±3%.

[0106] In some embodiments, a Yb:YAG laser is used as the compressor input. The laser output parameters are: single pulse energy 1 mJ, initial pulse width 700 fs, central wavelength 1030 nm, repetition rate 20 kHz. The laser output beam quality (M 2 The chirp factor is optimized to <1.1 to ensure the uniformity of the light field for subsequent nonlinear compression. Two chirped mirrors are used for multi-pass (8-pass) dispersion compensation, and the chirp of a single mirror is -1000 fs. 2 @1030 nm, reflectivity >99.8%. Cumulative compensation of total dispersion -8000 fs². Output pulse spectrum broadened to 1010–1045 nm. The corresponding spectral changes before and after compression are as follows: Figure 8 The output pulse is characterized using an autocorrelator, and the characterization results of the compressed pulse are shown in Figure 9 shown.

[0107] See also Figure 10 As shown, Figure 10Schematic diagram of the structure of a nonlinear pulse compression device 200 based on a multi-pass cavity on an annular tire surface, provided in an embodiment of the present application. This nonlinear pulse compression device 200 is used to perform the steps of the nonlinear pulse compression method based on a multi-pass cavity on an annular tire surface as described in the various embodiments above. This nonlinear pulse compression device 200 can be a single server or a server cluster, or it can be a terminal, such as a handheld terminal, a laptop computer, a wearable device, or a robot.

[0108] like Figure 10 As shown, the nonlinear pulse compression device 200 based on the annular tire surface multi-pass cavity includes:

[0109] An astigmatism correction unit 201 is configured to use an annular tire surface multi-pass cavity as a core component for nonlinear pulse compression, wherein the annular tire surface multi-pass cavity adopts a closed annular optical path, and a tire surface is machined on the cavity surface corresponding to the annular cavity of the annular cavity to correct astigmatism;

[0110] The cavity surface coating unit 202 is used to coat a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the annular cavity to avoid the introduction of positive chirp or nonlinear chirp during pulse reflection;

[0111] A medium insertion unit 203 is used to insert a solid medium or an inert gas into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity;

[0112] a pulse injection unit 204 for injecting a pulse to be compressed into the multi-pass cavity of the annular tire surface, and changing the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle, so as to adjust the optical path and intensity of the nonlinear effect;

[0113] The compression implementation unit 205 is used to perform dispersion compensation on the pulse that has undergone nonlinear spectral broadening through the annular tire surface multi-pass cavity to achieve pulse compression; wherein, the closed annular optical path of the annular tire surface multi-pass cavity reduces the optical path detuning caused by vibration or temperature fluctuation, the closed optical axis characteristic reduces the debugging complexity of the optical path alignment, and under the same optical path, the length of the annular tire surface multi-pass cavity is shorter than that of a traditional Herriott cavity.

[0114] In some embodiments, the step of coating a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the ring cavity includes: designing the film layer structure of the dielectric film or metal film based on the central wavelength, spectral bandwidth, and target chirp compensation amount of the pulse to be compressed, so that the film layer provides low-chirp or negative-chirp reflection characteristics that match the pulse chirp characteristics within the spectral range of the pulse; wherein the chirp amount of the negatively chirped film layer complements the positive chirp introduced by the nonlinear effect in the ring cavity, so as to synchronously compensate for the transmission chirp during the pulse spectrum broadening process, thereby reducing the number of extra-cavity dispersion compensation elements used.

[0115] In some embodiments, a solid medium or an inert gas is inserted into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity, including: when the nonlinear medium is a solid medium, a crystal or glass material with a matching nonlinear coefficient is selected, the size of the solid medium is adapted to the optical path of the annular cavity, and the intensity of the nonlinear effect is regulated by adjusting the material refractive index or doping concentration of the solid medium; when the nonlinear medium is an inert gas, the gas filling pressure of the annular cavity is controlled within the range of 10 kPa to 1 MPa, and the nonlinear coefficient is adjusted by changing the gas type and filling pressure to match the nonlinear spectral broadening requirements of the compressed pulses with different energies and pulse widths.

[0116] In some embodiments, the step of injecting the pulse to be compressed into the annular tire surface multi-pass cavity includes: pre-optimizing the beam quality of the pulse to be compressed to ensure the uniformity of the light field of the incident light beam; utilizing the closed optical axis characteristics of the annular tire surface multi-pass cavity to achieve automatic alignment of the optical path through single-incident calibration, without relying on a three-dimensional adjustment frame for precise angle adjustment, thereby reducing the debugging complexity of the incident end.

[0117] Exemplarily, the adjustment of the incident angle changes the number of reflections of the pulse to be compressed in the cavity to adjust the optical path and intensity of the nonlinear effect, including: establishing a correspondence model between the incident angle and the number of reflections, and dynamically changing the number of reflections of the pulse to be compressed in the multi-pass cavity of the annular tire surface within a preset range by adjusting the incident angle; calculating the required number of reflections through the correspondence model according to the pulse width after compression of the target pulse and the nonlinear spectrum broadening requirements, and matching the corresponding incident angle to linearly tune the optical path and intensity of the nonlinear effect, thereby achieving flexible control of the pulse width.

[0118] In some embodiments, the dispersion compensation is performed on the pulse that has completed nonlinear spectral broadening after passing through the annular tire tread multi-pass cavity to achieve pulse compression, including: using a chirped mirror pair to perform dispersion compensation, and the chirp amount of a single piece of the chirped mirror pair is matched and designed according to the pre-compensated chirp amount of the annular cavity membrane layer and the pulse bandwidth after spectral broadening, wherein the cumulative compensated total dispersion amount offsets the positive dispersion and transmission chirp introduced by the pulse during the nonlinear spectral broadening process; when the negative chirp provided by the annular cavity membrane layer has partially compensated for the pulse chirp, the number of lenses of the chirped mirror pair is reduced, so that the dispersion compensation process only requires 1-2 chirped mirrors to complete the total dispersion compensation, thereby simplifying the dispersion compensation system structure.

[0119] In some embodiments, before performing dispersion compensation on the pulses that have completed nonlinear spectral broadening through the annular tire surface multi-pass cavity, the method further includes: using the tire surface to correct the astigmatism during light beam transmission to improve the output light beam quality; and compensating for chirp during pulse spectral broadening through the low-chirp or negative-chirp dielectric film or metal film to reduce the number of chirped mirrors used outside the cavity.

[0120] It should be noted that, those skilled in the art can clearly understand that, for the sake of convenience and brevity of description, the above-described nonlinear pulse compression device based on the annular tire surface multi-pass cavity and the specific working processes of each module can refer to the corresponding processes in the embodiments of the nonlinear pulse compression method based on the annular tire surface multi-pass cavity described in the above-mentioned embodiments, and will not be repeated here.

[0121] The above-mentioned nonlinear pulse compression method based on the multi-pass cavity of the annular tire surface can be implemented in the form of a computer program. The computer program can be used in Figure 10 Run on the device shown.

[0122] See also Figure 11 , Figure 11 1 is a schematic block diagram of the structure of a control module provided in an embodiment of the present application. The control module includes a processor, a memory and a network interface connected via a device bus, wherein the memory may include a storage medium and an internal memory.

[0123] The storage medium can store an operating device and a computer program. The computer program includes program instructions, which, when executed, can cause the processor to perform any nonlinear pulse compression method based on a multi-pass cavity on a toroidal tire surface.

[0124] The processor is used to provide computing and control capabilities and support the operation of the entire control module.

[0125] The internal memory provides an environment for running the computer program in the non-volatile storage medium. When the computer program is executed by the processor, the processor can execute any nonlinear pulse compression method based on the annular tire surface multi-pass cavity.

[0126] The network interface is used for network communication, such as sending assigned tasks, etc. Those skilled in the art will understand that Figure 11 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the terminal to which the solution of the present application is applied. The specific control module may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0127] It should be understood that the processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc.

[0128] In one embodiment, the processor is configured to execute a computer program stored in the memory to implement the following steps:

[0129] An annular tire surface multi-pass cavity is used as the core component of nonlinear pulse compression. The annular tire surface multi-pass cavity adopts a closed annular optical path. The cavity surface of the annular tire surface multi-pass cavity corresponding to the annular cavity is processed with a tire surface to correct astigmatism.

[0130] A low-chirp or negative-chirp dielectric film or metal film is plated on the cavity surface of the annular cavity to avoid the introduction of positive chirp or nonlinear chirp during pulse reflection;

[0131] Inserting a solid medium or an inert gas into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity;

[0132] injecting a pulse to be compressed into the multi-pass cavity of the annular tire surface, and changing the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle to adjust the optical path and intensity of the nonlinear effect;

[0133] Dispersion compensation is performed on pulses that have undergone nonlinear spectral broadening through the annular tire surface multi-pass cavity to achieve pulse compression. The closed annular optical path of the annular tire surface multi-pass cavity reduces optical path detuning caused by vibration or temperature fluctuations, and the closed optical axis characteristic reduces the debugging complexity of optical path alignment. Moreover, under the same optical path, the length of the annular tire surface multi-pass cavity is shorter than that of a traditional Herriott cavity.

[0134] In some embodiments, the step of coating a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the ring cavity includes: designing the film layer structure of the dielectric film or metal film based on the central wavelength, spectral bandwidth, and target chirp compensation amount of the pulse to be compressed, so that the film layer provides low-chirp or negative-chirp reflection characteristics that match the pulse chirp characteristics within the spectral range of the pulse; wherein the chirp amount of the negatively chirped film layer complements the positive chirp introduced by the nonlinear effect in the ring cavity, so as to synchronously compensate for the transmission chirp during the pulse spectrum broadening process, thereby reducing the number of extra-cavity dispersion compensation elements used.

[0135] In some embodiments, a solid medium or an inert gas is inserted into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity, including: when the nonlinear medium is a solid medium, a crystal or glass material with a matching nonlinear coefficient is selected, the size of the solid medium is adapted to the optical path of the annular cavity, and the intensity of the nonlinear effect is regulated by adjusting the material refractive index or doping concentration of the solid medium; when the nonlinear medium is an inert gas, the gas filling pressure of the annular cavity is controlled within the range of 10 kPa to 1 MPa, and the nonlinear coefficient is adjusted by changing the gas type and filling pressure to match the nonlinear spectral broadening requirements of the compressed pulses with different energies and pulse widths.

[0136] In some embodiments, the step of injecting the pulse to be compressed into the annular tire surface multi-pass cavity includes: pre-optimizing the beam quality of the pulse to be compressed to ensure the uniformity of the light field of the incident light beam; utilizing the closed optical axis characteristics of the annular tire surface multi-pass cavity to achieve automatic alignment of the optical path through single-incident calibration, without relying on a three-dimensional adjustment frame for precise angle adjustment, thereby reducing the debugging complexity of the incident end.

[0137] Exemplarily, the adjustment of the incident angle changes the number of reflections of the pulse to be compressed in the cavity to adjust the optical path and intensity of the nonlinear effect, including: establishing a correspondence model between the incident angle and the number of reflections, and dynamically changing the number of reflections of the pulse to be compressed in the multi-pass cavity of the annular tire surface within a preset range by adjusting the incident angle; calculating the required number of reflections through the correspondence model according to the pulse width after compression of the target pulse and the nonlinear spectrum broadening requirements, and matching the corresponding incident angle to linearly tune the optical path and intensity of the nonlinear effect, thereby achieving flexible control of the pulse width.

[0138] In some embodiments, the dispersion compensation is performed on the pulse that has completed nonlinear spectral broadening after passing through the annular tire tread multi-pass cavity to achieve pulse compression, including: using a chirped mirror pair to perform dispersion compensation, and the chirp amount of a single piece of the chirped mirror pair is matched and designed according to the pre-compensated chirp amount of the annular cavity membrane layer and the pulse bandwidth after spectral broadening, wherein the cumulative compensated total dispersion amount offsets the positive dispersion and transmission chirp introduced by the pulse during the nonlinear spectral broadening process; when the negative chirp provided by the annular cavity membrane layer has partially compensated for the pulse chirp, the number of lenses of the chirped mirror pair is reduced, so that the dispersion compensation process only requires 1-2 chirped mirrors to complete the total dispersion compensation, thereby simplifying the dispersion compensation system structure.

[0139] In some embodiments, before performing dispersion compensation on the pulses that have completed nonlinear spectral broadening through the annular tire surface multi-pass cavity, the method further includes: using the tire surface to correct the astigmatism during light beam transmission to improve the output light beam quality; and compensating for chirp during pulse spectral broadening through the low-chirp or negative-chirp dielectric film or metal film to reduce the number of chirped mirrors used outside the cavity.

[0140] The present application also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the processor implements the steps of the nonlinear pulse compression method based on the annular tire surface multi-pass cavity as provided in any embodiment of the present application.

[0141] The computer-readable storage medium may be an internal storage unit of the control module described in the aforementioned embodiment, such as a hard disk or memory of the control module. The computer-readable storage medium may also be an external storage device of the control module, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the control module.

[0142] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present application, and such modifications or substitutions should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A nonlinear pulse compression method based on a multi-pass cavity on an annular tire surface, characterized in that: include: An annular tire surface multi-pass cavity is used as the core component of nonlinear pulse compression. The annular tire surface multi-pass cavity adopts a closed annular optical path. The cavity surface of the annular tire surface multi-pass cavity corresponding to the annular cavity is processed with a tire surface to correct astigmatism. A low-chirp or negative-chirp dielectric film or metal film is plated on the cavity surface of the annular cavity to avoid the introduction of positive chirp or nonlinear chirp during pulse reflection; Inserting a solid medium or an inert gas into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity; injecting a pulse to be compressed into the multi-pass cavity of the annular tire surface, and changing the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle to adjust the optical path and intensity of the nonlinear effect; Dispersion compensation is performed on pulses that have undergone nonlinear spectral broadening through the annular tire surface multi-pass cavity to achieve pulse compression. The closed annular optical path of the annular tire surface multi-pass cavity reduces optical path detuning caused by vibration or temperature fluctuations, and the closed optical axis characteristic reduces the debugging complexity of optical path alignment. Moreover, under the same optical path, the length of the annular tire surface multi-pass cavity is shorter than that of a traditional Herriott cavity.

2. The method according to claim 1, characterized in that The step of plating a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the annular cavity comprises: Designing the film structure of the dielectric film or metal film according to the central wavelength, spectral bandwidth and target chirp compensation amount of the pulse to be compressed so that the film layer provides low chirp or negative chirp reflection characteristics that match the chirp characteristics of the pulse within the spectral range of the pulse; The chirp of the negatively chirped dielectric film complements the positive chirp introduced by the nonlinear effect in the ring cavity, so as to synchronously compensate for the transmission chirp during the pulse spectrum broadening process and reduce the number of extracavity dispersion compensation elements used.

3. The method according to claim 1, characterized in that The method of inserting a solid medium or an inert gas into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity includes: When the nonlinear medium is a solid medium, a crystal or glass material with matching nonlinear coefficients is selected, the size of the solid medium is adapted to the optical path of the annular cavity, and the nonlinear effect intensity is controlled by adjusting the material refractive index or doping concentration of the solid medium; When the nonlinear medium is an inert gas, the gas filling pressure of the annular cavity is controlled within a range of 10 kPa to 1 MPa. The nonlinear coefficient is adjusted by changing the gas type and filling pressure to match the nonlinear spectrum broadening requirements of the compressed pulses with different energies and pulse widths.

4. The method according to claim 1, wherein The step of injecting the pulse to be compressed into the multi-pass cavity of the annular tire surface comprises: Pre-optimizing the beam quality of the pulse to be compressed to ensure the uniformity of the light field of the incident beam; By utilizing the closed optical axis characteristics of the annular tire surface multi-pass cavity, automatic optical path alignment is achieved through single-incident calibration, without relying on a three-dimensional adjustment frame for precise angle adjustment, thereby reducing the debugging complexity of the incident end.

5. The method according to claim 4, characterized in that The adjusting of the incident angle changes the number of reflections of the pulse to be compressed in the cavity, so as to adjust the optical path and intensity of the nonlinear effect, including: Establishing a corresponding relationship model between the incident angle and the number of reflections, and dynamically changing the number of reflections of the pulse to be compressed in the multi-pass cavity of the annular tire surface within a preset range by adjusting the incident angle; According to the pulse width after target pulse compression and the nonlinear spectrum broadening requirements, the required number of reflections is calculated through the corresponding relationship model, and the corresponding incident angle is matched to linearly tune the optical path and intensity of the nonlinear effect to achieve flexible control of the pulse width.

6. The method according to claim 1, characterized in that The method of performing dispersion compensation on the pulses that have undergone nonlinear spectrum broadening through the annular tire surface multi-pass cavity to achieve pulse compression includes: A chirped mirror pair is used for dispersion compensation. The chirp of each mirror is designed to match the pre-compensated chirp of the ring cavity membrane layer and the pulse bandwidth after spectral broadening. The cumulative total dispersion compensated offsets the positive dispersion and transmission chirp introduced by the nonlinear spectral broadening process of the pulse. When the negative chirp provided by the annular cavity membrane layer has partially compensated for the pulse chirp, the number of lenses in the chirped mirror pair is reduced, so that the dispersion compensation process only requires 1-2 chirped mirrors to complete the total dispersion compensation, simplifying the dispersion compensation system structure.

7. The method according to claim 1, characterized in that Before performing dispersion compensation on the pulses that have completed nonlinear spectrum broadening through the annular tire tread multi-pass cavity, the method further comprises: The tire surface is used to correct astigmatism during light beam transmission, thereby improving the output light beam quality; The low-chirp or negative-chirp dielectric film or metal film is used to compensate for chirp during the pulse spectrum broadening process, thereby reducing the number of extra-cavity chirped mirrors used.

8. A nonlinear pulse compression device based on a multi-pass cavity on an annular tire surface, characterized in that: include: An astigmatism correction unit is used to use an annular tire surface multi-pass cavity as a core component of nonlinear pulse compression, wherein the annular tire surface multi-pass cavity adopts a closed annular optical path, and the cavity surface of the annular tire surface multi-pass cavity corresponding to the annular cavity is processed with a tire surface for astigmatism correction; a cavity surface coating unit, used for coating a low-chirp or negative-chirp dielectric film or metal film on the cavity surface of the annular cavity to avoid the introduction of positive chirp or nonlinear chirp during pulse reflection; a medium insertion unit, used for inserting a solid medium or an inert gas into the annular cavity as a nonlinear medium to regulate the nonlinear effect in the multi-pass cavity; a pulse injection unit, configured to inject a pulse to be compressed into the multi-pass cavity of the annular tire surface, and change the number of reflections of the pulse to be compressed in the cavity by adjusting the incident angle, so as to adjust the optical path and intensity of the nonlinear effect; A compression implementation unit is used to perform dispersion compensation on pulses that have undergone nonlinear spectral broadening through the annular tire surface multi-pass cavity to achieve pulse compression; wherein the closed annular optical path of the annular tire surface multi-pass cavity reduces optical path detuning caused by vibration or temperature fluctuations, the closed optical axis characteristic reduces the debugging complexity of optical path alignment, and under the same optical path, the length of the annular tire surface multi-pass cavity is shorter than that of a traditional Herriott cavity.

9. A control module, characterized in that: The control module includes a memory and a processor; The memory is used to store computer programs; The processor is configured to execute the computer program and implement the method according to any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, which, when executed by a processor, causes the processor to implement the method according to any one of claims 1 to 7.

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