Laser pulse width online stabilization device and method

Abstract

The present invention discloses a laser pulse width online stabilization device and method to solve the problem that during laser processing, the laser pulse width is unstable due to environmental influences, resulting in inconsistent dimensions and poor quality of the processed products. Specifically, the device comprises a pulse width stretching module, a pulse width compression module, a laser detection module, and a controller, which are sequentially arranged on the optical path of the incident laser; the pulse width stretching module comprises two first adjustment platforms and two positive dispersion chirped mirrors arranged oppositely and parallel to the active ends of the two first adjustment platforms; the pulse width compression module comprises a second adjustment platform and two negative dispersion gratings arranged oppositely and parallel to the active ends of the two second adjustment platforms; the laser detection module comprises a beam splitter and a detector; the beam splitter divides the output laser of the pulse width compression module into a detection laser and a processing laser; the detector is arranged on the optical path of the detection laser; and the controller is respectively connected to the two first adjustment platforms, the two second adjustment platforms, and the detector.

Description

Technical Field

[0001] The present invention relates to a laser pulse width stabilization device, and in particular to a laser pulse width online stabilization device and method. Background Art

[0002] Ultrashort laser pulses, characterized by their ultrashort duration and ultra-intensity, offer irreplaceable advantages for machining complex three-dimensional structures and difficult-to-machine materials. However, considering the generation mechanism of ultrashort lasers, in actual laser processing, factors such as thermal effects on the laser's internal pulse width control components, thermal gradients in cooling, mechanical vibrations, dispersion and nonlinear effects in the optical system during beam propagation, and dispersion effects in the air can all cause variations in the ultrafast laser pulse width. For example, during laser transmission, dispersion and nonlinear effects can occur in many transmitting optical components (scientists have shown that ultrafast lasers in 1 cm of glass can cause a 100 fs pulse to broaden by approximately 200 fs) or in air (3 m of air can cause a 5 fs pulse to broaden to approximately 15 fs), causing the laser pulse width to broaden. This can severely degrade the dimensional consistency and quality (roughness, heat-affected zone) of the laser-machined structures. Due to the complex mechanism, the causes of any particular pulse width effect are also complex. Analyzing the causes during the formation process and compensating for them individually would be a massive undertaking, making this approach unrealistic. Therefore, it is extremely necessary to study the online detection and stabilization technology of ultrafast laser pulse width. Summary of the Invention

[0003] The purpose of the present invention is to provide a laser pulse width online stabilization device and method to solve the technical problem that during laser processing, the laser pulse width is unstable due to environmental influences, resulting in inconsistent product size and poor quality.

[0004] In order to achieve the above-mentioned object, the present invention provides a laser pulse width online stabilization device, which is special in that it comprises a pulse width stretching module, a pulse width compression module, a laser detection module and a controller which are sequentially arranged on the optical path of the incident laser;

[0005] The pulse width stretching module includes two first adjustment platforms and two positive dispersion chirped mirrors respectively arranged at the active ends of the two first adjustment platforms; the two positive dispersion chirped mirrors are arranged opposite and parallel to each other in the optical path of the incident laser; the two first adjustment platforms are used to adjust the angles of the two positive dispersion chirped mirrors accordingly, thereby adjusting the number of reflections of the laser beam between the two positive dispersion chirped mirrors;

[0006] The pulse width compression module includes a second adjustment platform and two negative dispersion gratings respectively arranged at the active ends of the two second adjustment platforms; the two negative dispersion gratings are arranged opposite and parallel to each other on the output light path of the pulse width stretching module; the two second adjustment platforms are used to correspondingly adjust the angle and / or distance of the two negative dispersion gratings;

[0007] The laser detection module includes a beam splitter and a detector; the beam splitter is arranged on the output light path of the pulse width compression module, and is used to split the laser beam after passing through the pulse width stretching module and the pulse width compression module into detection laser and processing laser; the detector is arranged on the light path where the detection laser is located, and is used for real-time detection;

[0008] The controller is connected to the two first adjustment platforms, the two second adjustment platforms and the detector respectively, and is used to control the two first adjustment platforms and the two second adjustment platforms to adjust the processing laser according to the laser signals detected by the detector.

[0009] Furthermore, the pulse width stretching module also includes two third adjustment platforms and translation compensation mirrors respectively arranged at the active ends of the two third adjustment platforms. The two translation compensation mirrors are sequentially located on the optical path after the two positive dispersion chirped mirrors and are used to translate the laser optical axis after the two positive dispersion chirped mirrors; the two third adjustment platforms are both connected to the controller.

[0010] Furthermore, the two translation compensation mirrors are a pair of optical wedges or a pair of parallel flat mirrors.

[0011] Furthermore, the pulse width compression module further includes a high-low mirror, a first reflecting mirror and a second reflecting mirror;

[0012] The height mirror and the first reflector are respectively located on both sides of the two negative dispersion gratings, and are respectively located on the optical path of the laser beam reflected by the two negative dispersion gratings; the second reflector is located on the optical path of the laser beam reflected by the height mirror; so that the laser beam after passing through the pulse width broadening module passes through the two negative dispersion gratings, the first reflector, the two negative dispersion gratings, the height mirror and the second reflector in sequence to reach the beam splitter, and the direction of the incident laser is the same as that of the processing laser.

[0013] Furthermore, the first reflector is a cubic corner cube prism;

[0014] The second reflector is a plane reflector.

[0015] Furthermore, the detector is a two-photon photodetector or a multi-photon photodetector;

[0016] The first adjustment platform and the second adjustment platform are both electric displacement platforms.

[0017] The present invention also provides a method for online stabilization of laser pulse width, which is special in that it includes the following steps:

[0018] Step 1: preset pulse width value;

[0019] Preset the pulse width value required for laser processing to the controller;

[0020] Step 2: Zero calibration;

[0021] The pulse width of the incident laser is measured and sent to the controller. The detector detects the pulse width of the detection laser and sends it to the controller. The controller compares the pulse width difference between the incident laser and the detection laser, and controls and adjusts the two first adjustment platforms and / or the two second adjustment platforms according to the pulse width difference, so that the laser beam is reflected only once between the two positive dispersion chirped mirrors and the pulse width detected by the detector is equal to the preset pulse width value.

[0022] Step 3: Real-time detection and online adjustment;

[0023] The processing laser is used for processing, the detector detects the pulse width of the detection laser in real time and sends it to the controller, and the controller compares the pulse width of the detection laser with the preset pulse width value in real time;

[0024] If the pulse width of the detection laser is greater than the preset pulse width value, pulse width broadening occurs. The controller adjusts the two second adjustment platforms according to the comparison result, and then adjusts the distance between the two negative dispersion gratings so that the detection laser pulse width detected by the detector is equal to the preset pulse width value;

[0025] If the pulse width of the detection laser is less than the preset pulse width value, pulse width compression occurs. The controller adjusts the two first adjustment platforms based on the comparison results, and then adjusts the angles of the two positive dispersion chirped mirrors, changing the number of reflections of the laser beam between the two positive dispersion chirped mirrors, so that the detection laser pulse width detected by the detector is equal to the preset pulse width value.

[0026] Furthermore, in step 2, a standard autocorrelator is specifically used to measure the pulse width of the incident laser.

[0027] Beneficial effects of the present invention:

[0028] 1. The present invention sets a pulse width stretching module, a pulse width compression module and a laser detection module between the incident laser and the processing laser. The pulse width stretching module adjusts different stretching amounts by controlling the angles of two positive dispersion chirped mirrors. The pulse width compression module achieves laser pulse width compression by controlling the distance between two negative dispersion gratings. The laser detection module detects the pulse width of the processing laser in real time and provides real-time feedback adjustment. The laser pulse width stabilization device substantially improves the stability of the processing laser, improves processing accuracy, greatly ensures the consistency of the laser processing structure size, and improves the quality of the processed products. It can effectively control the significant thermal effects (recasting, cracking, recrystallization, etc.) caused by pulse width stretching during laser processing, and avoid reducing the roughness of the material surface.

[0029] 2. The laser pulse width online stabilization device provided by the present invention integrates the pulse width stretching module and the pulse width compression module into a common optical path device, without involving a switching device in the middle, thereby improving the efficiency of online pulse width stabilization.

[0030] 3. The pulse width stretching module of the present invention adopts a positive dispersion chirped mirror with flexible angle adjustment, which can achieve the adjustment of different pulse width stretching amounts.

[0031] 4. The present invention configures two adjustable translation compensation mirrors in the pulse width stretching module. By adjusting the distance or angle of the two translation compensation mirrors, the optical axis offset caused by different pulse width stretching amounts can be compensated to the greatest extent.

[0032] 5. The present invention places the laser detection module close to the processing laser, that is, adopts a front-end compensation and back-end detection structural design, thus ensuring the stability of the processing laser pulse width to the greatest extent.

[0033] 6. The present invention also provides a high-low mirror, a first reflector, and a second reflector in the pulse width compression module. The high-low mirror can raise the laser beam, make the optical path more compact, and avoid interference with the laser beam. In addition, the combination of the high-low mirror, the first reflector, the second reflector and the two negative dispersion gratings makes the entire stabilization device more compact, which is convenient for integration into the whole machine or experimental system.

[0034] 7. The present invention uses a cubic corner cone reflection prism, which reduces the installation accuracy requirements and improves the stability of the laser beam during use. Even if the cubic corner cone reflection prism is slightly tilted during use, the direction of the reflected laser beam will always be parallel to the incident laser beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the structure of an embodiment of a laser pulse width online stabilization device of the present invention (the first to third adjustment platforms and the controller are not shown in the figure);

[0036] Figure 2 1 is a schematic diagram of the principle of translating the laser optical axis when the two translation compensation mirrors in the embodiment of the present invention are a pair of optical wedges;

[0037] Figure 3 This is a principle diagram of translating the laser optical axis when the two translation compensation mirrors in the embodiment of the present invention are a pair of parallel flat mirrors.

[0038] Figure Number:

[0039] 01-Incident laser. 02-Detection laser, 03-Processing laser;

[0040] 1-Pulse width stretching module, 11-Positive dispersion chirped mirror, 12-Translation compensation mirror, 2-Pulse width compression module, 21-Negative dispersion grating, 22-High-low mirror, 23-First reflector, 24-Second reflector, 3-Laser detection module, 31-Beam splitter, 32-Detector. DETAILED DESCRIPTION

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] In the field of laser processing, there are no related technologies, methods, or devices for online stabilization of laser pulse width. However, as a correction for pulse width fluctuations, laser pulse width stretching and compression technologies are used. This technology is mainly used in laser technology and can be divided into three categories based on the principle:

[0043] First, prism pairs can effectively compensate for group delay dispersion (GDD), but the high-order dispersion of the gain medium and prism material itself is not fully compensated. At the same time, as the pulse width becomes narrower and the bandwidth widens, the existing dispersion compensation elements cannot fully compensate for the various orders of dispersion within the wide bandwidth. When the stretch ratio reaches 10 4 When the prism size is too large for wide-spectrum femtosecond laser pulses, the device will be very bulky due to the large amount of material inserted into the second prism. In addition, the large amount of positive dispersion introduced by the second prism will reduce the broadening capability of the prism pair.

[0044] Second, grating pairs can achieve pulse width expansion or compression by adjusting the spacing of the grating pairs and the incident angle. They have the advantages of providing high group velocity dispersion and a large pulse width control range. However, they cannot completely compensate for the high-order dispersion introduced by the material during the amplification process, so Fourier transform-limited compressed pulses cannot be obtained. In addition, the low transmission efficiency of the grating will result in a large amount of energy loss.

[0045] Third, the chirped mirror can make the balance of high-order dispersion in the cavity more effective, ensure the high reflectivity of the mirror itself, and have the required group velocity dispersion (GVD) compensation over a wider wavelength range. Therefore, it can obtain relatively complete dispersion compensation over a wider spectral range, thereby supporting the formation of shorter laser pulses.

[0046] Although the principles of laser pulse width broadening and compression are divided into the above three categories, from the perspective of laser technology, different laser types and dispersion correction requirements can lead to different broadening and compression schemes based on the above three principles. The specific number of optical elements, technical indicators, design layout, etc. vary greatly.

[0047] It is worth noting that the present invention mainly needs to solve the pulse width error generated by the incident laser emitted by the laser during the optical path propagation process. The error characteristics of its pulse width (such as pulse width jitter type, amplitude, etc.) are quite different from those of laser technology. Therefore, the present invention will only use its basic principles, but its specific solutions and methods are quite different from laser pulse width compression and broadening, which are introduced in detail below.

[0048] The present invention addresses the problems of nonlinear effects, gradient thermal effects, environmental disturbances and other problems in existing laser processing optical elements that easily cause unstable laser pulse width (broadening, compression), reduces the dimensional accuracy, quality (thermal effects, processing consistency) and other problems of laser processing products, quantitatively analyzes the broadening or compression of the pulse width and considers its comprehensive effects to achieve online stabilization of the femtosecond laser pulse width. The invention mainly adopts a back-end detection and front-end compensation structural design, that is, the laser detection module is placed at the end of the entire optical path, and the pulse width broadening module and pulse width compression module for laser compensation are placed at the front of the entire optical path. A two-photon photodetector is used to first detect the light beam pulse width. If pulse width broadening occurs, pulse width compression is achieved by adjusting two negative dispersion gratings. If pulse width compression occurs (this situation is rare), pulse width broadening is achieved by a pair of positive dispersion chirped mirrors, thereby achieving online stabilization of the pulse width.

[0049] Based on the above theory, the embodiment of the present invention provides a laser pulse width online stabilization device, such as Figure 1 As shown, the laser pulse width online stabilization device includes a pulse width stretching module 1, a pulse width compression module 2, a laser detection module 3 and a controller which are sequentially arranged on the optical path of the incident laser 01;

[0050] The pulse width stretching module 1 includes two first adjustment platforms and two positive dispersion chirped mirrors 11 respectively arranged at the active ends of the two first adjustment platforms; it also includes two third adjustment platforms and translation compensation mirrors 12 respectively arranged at the active ends of the two third adjustment platforms; the two positive dispersion chirped mirrors 11 are opposite and parallel; the two first adjustment platforms are used to adjust the angles of the two positive dispersion chirped mirrors 11 accordingly; combined with Figure 1 and Figure 2 、 Figure 3 As shown, the two translation compensation mirrors 12 are a pair of optical wedges or a pair of parallel flat mirrors, which are used to translate the laser optical axis after passing through the two positive dispersion chirped mirrors 11, so that the output light of the pulse width stretching module 1 is consistent with the optical axis of the laser beam entering the pulse width compression module 2.

[0051] Regarding the compensation of optical axis translation of wedge / parallel plate mirror: Figure 3 As shown in , the magnitude and direction of the translation compensation can be changed by adjusting the rotation angle of the parallel flat mirror; Figure 2 As shown, the magnitude of the translation compensation amount can also be changed by adjusting the distance between the optical wedge pair, and the direction of the translation compensation amount can be changed by rotating the optical wedge 180° along the optical axis.

[0052] The pulse width compression module 2 includes a second adjustment platform and two negative dispersion gratings 21 respectively arranged at the active ends of the two second adjustment platforms; it also includes a high and low mirror 22, a first reflector 23 and a second reflector 24; the two negative dispersion gratings 21 are relative and parallel; the two second adjustment platforms are used to adjust the angle and / or distance of the two negative dispersion gratings 21 accordingly; the high and low mirror 22 and the first reflector 23 are respectively located on both sides of the two negative dispersion gratings 21, and are respectively located on the optical path of the laser beam reflected by the two negative dispersion gratings 21; the second reflector 24 is located on the optical path of the laser beam reflected by the high and low mirror 22; so that the laser beam after passing through the pulse width widening module 1 passes through the two negative dispersion gratings 21, the first reflector 23, the two negative dispersion gratings 21, the high and low mirror 22 and the second reflector 24 in sequence to reach the beam splitter 31, and the direction of the incident laser 01 is the same as that of the processing laser 03.

[0053] The first reflector 23 can take two forms. A preferred option is a cubic corner-cone reflector. The principle is that a beam incident from the bottom in any direction, after being sequentially reflected by the three reflective surfaces, remains parallel to the incident beam, only shifted a certain distance. This has the advantage of requiring less precision for installation and greater laser beam stability during use. Even if the cubic corner-cone reflector is slightly tilted, the reflected laser beam remains parallel to the incident beam. Alternatively, a plane reflector can be used, but this requires more stringent installation than a cubic corner-cone reflector and is not as stable during use.

[0054] The pulse width stretching module 1 and the pulse width compression module 2 jointly realize the compensation of the pulse width, so that the emitted processing laser meets the index requirements and provides high-quality processing laser for laser processing. The stretching stage uses a pair of positive dispersion chirped mirrors to generate positive dispersion to achieve the widening of the laser pulse width. Each reflection will produce a fixed GVD. The dispersion amount is controlled by controlling the number of reflections to perform fixed time domain widening. For example, the GVD of a single reflection is 5000fs2. The angles of the two positive dispersion chirped mirrors can be adjusted online. By adjusting the angles of the two positive dispersion chirped mirrors, the number of reflections of the laser beam between the two positive dispersion chirped mirrors is achieved, thereby generating positive dispersion of different values ​​and performing corrections for different pulse width compression values. In addition, from Figure 1 It can be seen that the different reflection times between the two positive dispersion chirped mirrors will cause the laser beam emitted from the positive dispersion chirped mirror 11 to have different offsets along the optical axis. Therefore, in order to ensure that the pulse width stretching module 1 and the pulse width compression module 2 share the same optical path, a compensation module is set in the pulse width stretching module 1, namely, two third adjustment platforms and translation compensation mirrors 12 respectively set at the active ends of the two third adjustment platforms, as shown in FIG. Figure 2 As shown, this compensation module can achieve compensation for translations of varying magnitudes and directions by adjusting the distance between the wedge pair or the tilt angle of the parallel flat mirror. The pulse compression module 2 consists of two negative dispersion gratings 21, coupled with a high-low mirror 22, a first reflector 23, and a second reflector 24. Based on the pre-bias provided by the positive dispersion chirped mirror 11, the negative dispersion gratings 21 compensate for the deviation of the beam's dispersion using the difference in dispersion between the two. By controlling the distance between the two negative dispersion gratings 21, varying amounts of negative dispersion are generated, achieving laser pulse compression. To ensure a compact optical path, laser output is achieved through reflection from high-low mirrors.

[0055] The laser detection module 3's primary function is to measure the pulse width of the laser beam and provide real-time pulse width data to the controller online. The laser detection module 3 includes a beam splitter 31 and a detector 32. The beam splitter 31 is used to split the laser beam, after passing through the pulse width stretching module 1 and the pulse width compression module 2, into a detection laser 02 and a processing laser 03. The detector 32 is located in the optical path of the detection laser 02 and is used for real-time detection. The detector 32 is a two-photon photodetector or a multiphoton photodetector. In this embodiment, the detector 32 is a multiphoton photodetector.

[0056] The controller is connected to the two first adjustment platforms, two second adjustment platforms, two third adjustment platforms, and detector 32 via serial communication. It controls the two first adjustment platforms, two second adjustment platforms, and two third adjustment platforms to adjust the processing laser 03 based on the laser signals detected by detector 32. The first, second, and third adjustment platforms are all motorized displacement platforms. The controller establishes a closed loop between spot position detection and beam pointing control, reading and analyzing detection data and software-driven pulse width control to achieve real-time control of the laser pulse width and achieve stable pulse width compensation.

[0057] The working process of the above-mentioned laser pulse width online stabilization device is as follows:

[0058] Step 1: preset pulse width value;

[0059] Preset the pulse width value required for laser processing to the controller;

[0060] Step 2: Calibrate the zero position: First, use a standard autocorrelator to measure the corresponding pulse width and pulse shape. Based on this, calibrate the operating mode of the two-photon absorption autocorrelator. Using the calibrated pulse signal, adjust the angles of the two positive dispersion chirped mirrors 11 to ensure that the laser beam is reflected only once between the two positive dispersion chirped mirrors 11. At the same time, adjust the two second adjustment platforms to adjust the spacing between the two negative dispersion gratings 21 so that the pulse width detected by the detector is equal to the preset pulse width value, completing the module zero position calibration.

[0061] Step 3: System Self-Test: The user uses processing laser 02 for processing. During processing, the actual pulse width of processing laser 02 at each moment is extracted in real time through feedback signals from the photodetector. This pulse signal is then sent to control the movement of the motorized displacement platform (i.e., the first, second, and / or third adjustment platforms). During laser processing, the multi-photon photodetector's real-time pulse width monitoring function is activated (measured once per minute). The output pulse signal is compared with the set pulse width value in real time. Based on this comparison, the corresponding motorized platform is fine-tuned to stabilize the processing laser pulse width.

[0062] During control and adjustment, the controller needs to determine the direction of pulse width compensation and make the necessary compensation. After calibrating the laser's pulse width, the difference between the current processing laser pulse width and the preset pulse width can be determined, thereby confirming the direction and amount of compensation. The pulse width expansion process uses two positive dispersion chirped mirrors 11 to generate positive dispersion. By adjusting the rotation angle of the positive dispersion chirped mirrors 11 and the number of reflections, pulse width expansion is achieved. The pulse width compression process uses two negative dispersion gratings 12 to generate negative dispersion. By presetting the beam incident angle and adjusting the distance between the two negative dispersion gratings 12, a GVD is generated that is as conjugate as possible with the positive dispersion chirped mirrors, achieving pulse compression.

[0063] If the preset pulse width value set in step 1 is zero, then if a negative value appears in the detector 32, it means that pulse width compression occurs (compared with the zero-position pulse width). At this time, the two first adjustment platforms are adjusted, and then the angles of the two positive dispersion chirped mirrors 11 are adjusted, the number of reflections of the laser beam is changed, and the positive dispersion value is adjusted so that the detection value of the detector is returned to zero; if a positive value appears in the detector 32, pulse width broadening occurs. At this time, the two second adjustment platforms are adjusted to correspondingly adjust the distance between the two negative dispersion gratings 21, and then the negative dispersion value is adjusted so that the detection value of the detector 32 is returned to zero; in this way, the online pulse width of the processing laser is maintained stable.

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention shall be covered by the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A laser pulse width online stabilization device, characterized by: It comprises a pulse width stretching module (1), a pulse width compression module (2), a laser detection module (3) and a controller which are sequentially arranged on the optical path of the incident laser (01); The pulse width stretching module (1) comprises two first adjustment platforms and two positive dispersion chirped mirrors (11) respectively arranged at the active ends of the two first adjustment platforms; the two positive dispersion chirped mirrors (11) are arranged oppositely and in parallel on the optical path of the incident laser (01); the two first adjustment platforms are used to correspondingly adjust the angles of the two positive dispersion chirped mirrors (11), thereby adjusting the number of reflections of the incident laser (01) between the two positive dispersion chirped mirrors (11); The pulse width compression module (2) comprises a second adjustment platform and two negative dispersion gratings (21) respectively arranged at the active ends of the two second adjustment platforms; the two negative dispersion gratings (21) are arranged oppositely and in parallel on the output light path of the pulse width expansion module (1); the two second adjustment platforms are used to correspondingly adjust the angle and / or distance of the two negative dispersion gratings (21); The laser detection module (3) comprises a beam splitter (31) and a detector (32); the beam splitter (31) is arranged on the output optical path of the pulse width compression module (2) and is used to split the incident laser (01) after passing through the pulse width expansion module (1) and the pulse width compression module (2) into a detection laser (02) and a processing laser (03); the detector (32) is arranged on the optical path where the detection laser (02) is located and is used for real-time detection; The controller is connected to the two first adjustment platforms, the two second adjustment platforms and the detector (32) respectively, and is used to control the two first adjustment platforms and the two second adjustment platforms to adjust the processing laser (03) according to the laser signal detected by the detector (32); The pulse width stretching module (1) further comprises two third adjustment platforms and translation compensation mirrors (12) respectively arranged at the active ends of the two third adjustment platforms. The translation compensation mirrors (12) are sequentially located on the optical path after passing through the two positive dispersion chirped mirrors (11) and are used to translate the optical axis of the incident laser (01) after passing through the two positive dispersion chirped mirrors (11). Both the third adjustment platforms are connected to the controller.

2. The laser pulse width online stabilization device according to claim 1, characterized in that: The two translation compensation mirrors (12) are a pair of optical wedges or a pair of parallel flat mirrors.

3. The laser pulse width online stabilization device according to claim 1 or 2, characterized in that: The pulse width compression module (2) further includes a high-low mirror (22), a first reflecting mirror (23) and a second reflecting mirror (24); The high-low mirror (22) and the first reflector (23) are respectively located on both sides of the two negative dispersion gratings (21), and are respectively located on the optical path of the incident laser (01) reflected by the two negative dispersion gratings (21); the second reflector (24) is located on the optical path of the incident laser (01) reflected by the high-low mirror (22); the incident laser (01) after passing through the pulse width broadening module (1) passes through the two negative dispersion gratings (21), the first reflector (23), the two negative dispersion gratings (21), the high-low mirror (22) and the second reflector (24) in sequence to reach the beam splitter (31), and the direction of the incident laser (01) and the processing laser (03) are the same.

4. The laser pulse width online stabilization device according to claim 3, characterized in that: The first reflector (23) is a cubic corner cone reflector; The second reflector (24) is a plane reflector.

5. The laser pulse width online stabilization device according to claim 4, characterized in that: The detector (32) is a two-photon photodetector or a multi-photon photodetector; The first adjustment platform and the second adjustment platform are both electric displacement platforms.

6. A method for online stabilization of laser pulse width, using the laser pulse width online stabilization device according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: preset pulse width value; Preset the pulse width value required for laser processing to the controller; Step 2: Zero calibration; The pulse width of the incident laser (01) is measured and sent to the controller, the detector (32) detects the pulse width of the detection laser (02) and sends it to the controller, the controller compares the pulse width difference between the incident laser (01) and the detection laser (02), and controls and adjusts the two first adjustment platforms and / or the two second adjustment platforms according to the pulse width difference, so that the incident laser (01) is reflected only once between the two positive dispersion chirped mirrors (11), and the pulse width detected by the detector (32) is equal to a preset pulse width value; Step 3: Real-time detection and online adjustment; The processing laser (03) is used for processing, the detector (32) detects the pulse width of the detection laser (02) in real time and sends it to the controller, and the controller compares the pulse width of the detection laser (02) with a preset pulse width value in real time; If the pulse width of the detection laser (02) is greater than a preset pulse width value, pulse width broadening occurs, and the controller adjusts the two second adjustment platforms according to the comparison result, and further adjusts the distance between the two negative dispersion gratings (21), so that the pulse width of the detection laser (02) detected by the detector (32) is equal to the preset pulse width value; If the pulse width of the detection laser (02) is less than a preset pulse width value, pulse width compression occurs. The controller adjusts the two first adjustment platforms according to the comparison result, and further adjusts the angles of the two positive dispersion chirped mirrors (11), thereby changing the number of reflections of the incident laser (01) between the two positive dispersion chirped mirrors (11), so that the pulse width of the detection laser (02) detected by the detector (32) is equal to the preset pulse width value.

7. The laser pulse width online stabilization method according to claim 6, characterized in that: In step 2, a standard autocorrelator is specifically used to measure the pulse width of the incident laser (01).

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