Ultrafast laser time domain shaping and calibrating device

Abstract

The invention discloses an ultrafast laser time domain shaping and calibrating device, and belongs to the field of ultrafast laser processing. Comprising a time domain shaping module and a self-correlation calibration module, the time domain shaping module splits linearly polarized ultrafast laser into a fixed light arm and a delay light arm, regulates and controls double-pulse time delay through an optical delay line, independently controls laser parameters of the two light arms, and ensures mutual orthogonality of double-pulse polarization states; the self-correlation calibration module is connected with the time domain shaping module through a coaxial optical path, converts double pulses into second harmonic (SHG) signals through an II-type phase matching nonlinear crystal, collects SHG signal intensities under different time sequences through a scanning delay line, generates an intensity self-correlation curve, calibrates a delay zero point and calculates pulse width, and the time domain shaping module is connected with the time domain shaping module through a coaxial optical path. Measurement parameters are fed back to the time domain shaping module for correcting delay parameters. The device can be applied to an existing laser processing platform, a time domain shaping double-pulse laser processing function is provided, the heat accumulation phenomenon is effectively reduced, and the ultrafast laser processing quality is improved.

Description

Technical Field

[0001] This invention relates to the field of ultrafast laser processing, and in particular to an ultrafast laser time-domain shaping and calibration device. Background Technology

[0002] Ultrafast lasers have extremely short pulse widths (on the order of picoseconds to femtoseconds, i.e., 10^66 microseconds). -12 s to 10 -15 Ultrafast lasers, with their high instantaneous power and high intensity, serve as a crucial foundation for precision machining and pumped ultrafast imaging technologies, finding widespread applications in mechanics, materials science, optoelectronics, and biomedicine. In ultrafast laser processing, time-domain shaping methods can be used to control the electronic dynamics and thermal relaxation processes of materials, thereby reducing debris buildup, minimizing thermal effects, and improving processing quality. Time-domain shaped ultrafast lasers, as a fully optically controlled laser technology, are typically achieved through a series of operations such as beam splitting and delay (similar to a Michelson interferometer) to obtain a double-pulse ultrafast laser sequence with a picosecond time difference. However, due to factors such as optical path adjustment errors and uncertainties in the relative positions of components, finding the zero point of the time delay in the time-domain shaping system is difficult, leading to uncertainties in the ultrafast laser's time-domain parameters. Therefore, accurately calibrating the time-domain parameters, such as the delay between double pulses and the laser pulse width, is a key technical challenge in this field.

[0003] To address the time non-overlap problem in time-domain shaped ultrafast lasers, it is generally necessary to pre-calibrate the zero point of the delay line to obtain an accurate dual-pulse ultrafast laser sequence. Since the pulse width of ultrafast lasers is on the order of picoseconds or even femtoseconds, while the response time of conventional photodetectors is on the order of nanoseconds, the time series of ultrafast lasers cannot be directly measured on an oscilloscope using electrical signal methods. Current methods for measuring ultrafast laser time-domain parameters include intensity autocorrelation, interferometric autocorrelation, frequency-resolved optical switching (FROG), self-referenced spectral phase coherent electric field reconstruction (SPIDER), and a real-time measurement method and system for the duration of transient ultrashort pulses (CN 110567595A). While the FROG method can obtain complete ultrafast laser information, it requires complex iterative algorithms for post-processing, resulting in slow computation speed and the inability to measure individual pulses in real time. The SPIDER method and the "real-time measurement method for the duration of transient ultrashort pulses" cannot calibrate the zero point of the delay line due to the fixed optical path. In addition, the traditional intensity autocorrelation method has the problem of optical path separation and cannot be used for coaxial optical paths, which brings inconvenience to subsequent laser processing; the interference autocorrelation method based on coaxial optical paths has the coupling problem of autocorrelation components and interference components, and cannot solve for a unique pulse time domain distribution.

[0004] Therefore, there is an urgent need for an ultrafast laser time delay measurement method for coaxial optical path systems in order to measure and calibrate time-domain shaping laser systems. Summary of the Invention

[0005] To address the challenges of pulse width measurement and zero-delay calibration in time-domain shaped ultrafast lasers, this invention proposes an ultrafast laser time-domain shaping and calibration device. This device possesses two core functions: ultrafast laser dual-pulse generation and intensity autocorrelation calibration based on a coaxial optical path. By inserting attenuators, dispersive elements, waveplates, or nonlinear crystals into the optical arm, the energy, pulse width, polarization, and wavelength of the dual-pulse sequence can be independently controlled, enabling fully optically controlled ultrafast laser precision machining.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention proposes an ultrafast laser time-domain shaping and calibration device, comprising:

[0008] Time-domain shaping module: used to split linearly polarized ultrafast laser beams into fixed optical arms and delayed optical arms, adjust the time delay of the dual pulses through optical delay lines, and independently control the laser parameters of the two optical arms, wherein the polarization states of the laser pulses of the two optical arms are orthogonal to each other;

[0009] Autocorrelation calibration module: directly connected to the optical output of the time-domain shaping module via a coaxial optical path, and receives the double pulse sequence generated by the time-domain shaping module;

[0010] The autocorrelation calibration module includes a type II phase-matched nonlinear crystal for converting the received double pulses into second harmonic (SHG) signals; the time delay of the double pulses is changed by scanning the optical delay line in the time-domain shaping module to acquire SHG signal intensities under different timings; an intensity autocorrelation curve is generated based on the acquired SHG signal intensity distribution to calibrate the zero-delay point and calculate the pulse width;

[0011] The output of the time-domain shaping module is coupled to the laser processing platform and the autocorrelation calibration module to form a calibration feedback mechanism. The parameters measured by the autocorrelation calibration module are fed back to the time-domain shaping module to correct the delay parameters.

[0012] Preferably, the time-domain shaping module includes:

[0013] First beam splitter: used to split the incident ultrafast laser beam into a first laser pulse and a second laser pulse, which enter the fixed optical arm and the delayed optical arm respectively;

[0014] Fixed optical arm: Receives the first laser pulse from the first beam splitter, and is used to guide the propagation direction of the first laser pulse and control the polarization state of the first laser pulse;

[0015] Delayed optical arm: Receives the second laser pulse from the first beam splitter, and is used to guide the propagation direction of the second laser pulse and control the polarization state and the amount of time delay of the double pulse;

[0016] The second beam splitter is used to combine two laser pulses returning from the fixed optical arm and the delayed optical arm, respectively, to output a coaxial ultrafast laser double pulse sequence, which is then directed to the autocorrelation calibration module and the laser processing platform.

[0017] Preferably, the optical path of the fixed optical arm includes a first pair of mirrors, a first half-wave plate, and a first mirror in sequence. The first pair of mirrors serves as the optical path entrance, receiving the first laser pulse after it is split from the first beam splitter and guiding the optical path. The first half-wave plate modulates the polarization state of the first laser pulse to form a P-polarization state. The first mirror guides the polarization-modulated first laser pulse to the beam combining interface of the second beam splitter.

[0018] Preferably, the optical path of the delay arm includes, in sequence, a second mirror, a pair of second mirrors, an optical delay line, and a second half-wave plate. The second mirror serves as the optical path entrance, receiving the second laser pulse after it has been split by the first beam splitter and guiding the optical path. The pair of second mirrors is mounted on the optical delay line, changing the optical path length of the second laser pulse through linear displacement, thereby changing the time delay of the double pulse. The second half-wave plate is located between the optical delay line and the beam combining interface of the second beam splitter, controlling the polarization state of the second laser pulse to form an S-polarization state orthogonal to the first laser pulse.

[0019] Preferably, the optical delay line is a single-axis linear electric slide, and the time delay of the dual pulses is adjusted by controlling the displacement of the slide.

[0020] Preferably, the autocorrelation calibration module further includes a low-pass filter, a convex lens, and a detector. The low-pass filter is used to filter out residual fundamental frequency light and retain the harmonic SHG signal. The convex lens is used to focus the SHG signal onto the photosensitive surface of the detector, and the detector collects the SHG signal intensity.

[0021] Preferably, the calibration of the zero-point delay and calculation of the pulse width includes:

[0022] Scan the intensity autocorrelation curve and identify the peak point position x0 of the curve as the zero delay point;

[0023] The optical delay line displacement coordinate x is converted into the double pulse time delay Δt according to the formula Δt=(2x / c)-x0, where c is the speed of light;

[0024] The actual laser pulse width is calculated based on the proportional relationship between the pulse width and the full width at half maximum (FWHM) of the autocorrelation curve of intensity.

[0025] Preferably, it also includes an optical breadboard, and the time-domain shaping module and autocorrelation calibration module are all integrated on the optical breadboard to form an integrated structure.

[0026] Preferably, the type II phase-matching nonlinear crystal is a BBO, KTP, or LBO crystal, and the incident angle θ and azimuth angle φ of the nonlinear crystal are adjustable to meet the phase-matching condition.

[0027] Secondly, this invention proposes a time-domain shaping ultrafast laser system, comprising:

[0028] Ultrafast lasers are used to generate linearly polarized and pulse-width-tunable ultrafast lasers.

[0029] An ultrafast laser time-domain shaping and calibration device, the input of which receives the laser output from the ultrafast laser;

[0030] The laser processing platform is coupled to the output of the ultrafast laser time-domain shaping and calibration device, and is used to receive the time-domain shaped laser for processing.

[0031] The beneficial effects of this invention are:

[0032] This invention proposes an ultrafast laser time-domain shaping and calibration device, suitable for time-domain shaped ultrafast laser systems. It mainly includes a time-domain shaping module and an autocorrelation calibration module, which respectively realize the generation of ultrafast laser dual-pulse sequences and the calibration of time-domain parameters. Utilizing the type II phase-matching principle, intensity autocorrelation measurement can be achieved in a coaxial optical path system, solving the problem of spatial separation in traditional autocorrelation optical paths and improving its compatibility. This device can be applied to existing laser processing platforms, providing time-domain shaped dual-pulse laser processing capabilities, effectively reducing heat accumulation and improving the processing quality of ultrafast laser processing. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a time-domain shaping ultrafast laser system based on the ultrafast laser time-domain shaping and calibration device of the present invention;

[0034] Figure 2 This is a schematic diagram of the optical path principle for ultrafast laser time-domain shaping and calibration.

[0035] Figure 3 It is based on the coaxial SHG autocorrelation measurement principle of type II phase matching;

[0036] Figure 4 This is an assembly diagram of an integrated ultrafast laser time-domain shaping and calibration device;

[0037] Figure 5The results are SHG signal measurement results under different time delays. (a) is the FROG two-dimensional trace map, and (b) is the intensity autocorrelation map at wavelength λ = 520.85 nm.

[0038] In the diagram: 001-First broadband beam splitter prism, 002-Second broadband beam splitter prism, 003-Autocorrelation calibration module, 004-Optical breadboard, 101-First mirror pair, 102-First half-wave plate, 103-First mirror, 201-Second mirror, 202-Second mirror pair, 203-Optical delay line, 204-Second half-wave plate, 301-Third mirror, 302-Nonlinear crystal, 303-Low-pass filter, 304-Convex lens, 305-Detector, 306-Residual near-infrared light, 307-Green light, 308-Two-dimensional fine-tuning frame, 309-Single-axis slide, 310-Multimode fiber. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention or the claims of this invention without creative effort should fall within the scope of protection of this invention.

[0040] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components.

[0041] like Figure 1As shown, the ultrafast laser time-domain shaping and calibration device proposed in this invention includes a time-domain shaping module and an autocorrelation calibration module. Installed between the ultrafast laser and the laser processing platform, it can realize a time-domain shaped ultrafast laser system. The ultrafast laser provides the ultrafast laser source and can control the laser power, wavelength, repetition rate, and pulse width, outputting linearly polarized ultrafast laser light. This light typically undergoes preprocessing operations such as beam expansion, collimation, and filtering before entering the time-domain shaping module. The time-domain shaping module can split the linearly polarized ultrafast laser beam into a fixed optical arm and a delayed optical arm. It controls the double-pulse time delay Δt through an optical delay line and independently controls the laser parameters of the two optical arms, generating an ultrafast laser double-pulse sequence. It has two output ports: one outputs to the autocorrelation calibration module, and the other outputs to the laser processing platform. The autocorrelation calibration module can not only calibrate the zero-point position of the double-pulse time delay but also measure the ultrafast laser pulse width. The following will focus on describing the time-domain shaping module and the autocorrelation calibration module, with the specific optical path design as follows: Figure 2 As shown.

[0042] The time-domain shaping module includes a first beam-splitting prism 001, a second beam-splitting prism 002, a fixed optical arm, and a delayed optical arm. The first beam-splitting prism 001 splits the incident ultrafast laser beam into a first laser pulse and a second laser pulse, which enter the fixed optical arm and the delayed optical arm, respectively. The fixed optical arm receives the first laser pulse, and its optical path sequentially includes a first mirror pair 101, a first half-wave plate 102, and a first mirror 103. The first mirror pair 101 serves as the optical path entrance for guidance; the first half-wave plate 102 modulates the polarization state of the first laser pulse to form a P-polarization state; and the first mirror 103 guides the modulated pulse to the beam-combining interface of the second beam-splitting prism 002. The delayed optical arm receives the second laser pulse, and its optical path sequentially includes a second mirror 201, a second mirror pair 202, an optical delay line 203, and a second half-wave plate 204. The second reflector 201 serves as the optical path inlet for guiding the optical path. The second reflector pair 202 is mounted on the optical delay line 203, and its linear displacement alters the optical path, thereby controlling the time delay. The second half-wave plate 204 modulates the polarization state of the second laser pulse, making it S-polarized, orthogonal to the P-polarization state of the fixed optical arm. The second beam splitter 002 combines the two laser pulses returning from the fixed and delayed optical arms, outputting a coaxial dual-pulse sequence, which is then guided to the autocorrelation calibration module and the laser processing platform, respectively.

[0043] Specifically, the linearly polarized ultrafast laser, after beam expansion, collimation, and filtering preprocessing, is input to the time-domain shaping module through port 1. In the time-domain shaping module, the linearly polarized ultrafast laser is first split into two beams by a first beam splitter: the first laser pulse passes through a fixed pair of first reflectors 101, its polarization direction is adjusted by a first half-wave plate 102, and then coupled to a second beam splitter 002 via a first reflector 103; this optical path is called the fixed optical arm. The second laser pulse first passes through a second reflector 201, then through a pair of second reflectors 202 mounted on an optical delay line to guide the beam, its polarization direction is adjusted by a second half-wave plate 204, and finally coupled to the second beam splitter 002; this optical path is called the delayed optical arm. The two beams converge at the second beam splitter to form a double-pulse sequence, which is then output to the autocorrelation calibration module and the laser processing platform through ports 3 and 2. Here, the second beam splitter 002 can be a polarizing beam splitter to achieve proportional control of the laser energy of port 2 and port 3, and even to achieve a single-end output of only port 2 or port 3, so as to increase the laser energy utilization rate.

[0044] In the time-domain shaping module, by adding a half-wave plate to each of the fixed and delayed optical arms, the polarization states of the two beams can be independently controlled to meet the requirements of subsequent autocorrelation measurements.

[0045] In one specific embodiment of the present invention, the optical delay line can be a single-axis linear slide. By adjusting the position of the delay line, the relative distance difference between the fixed optical arm and the delay optical arm can be changed, thereby achieving control of the time delay Δt, as expressed by the following formula:

[0046]

[0047] In the formula, Δt is the time delay of the double pulse, ΔL is the displacement of the delay line, and c is the speed of light. In this embodiment, the delay line travel is ΔL = 100 mm, so the maximum delay that can generate a double pulse is Δt = 2ΔL / c = 0.667 ns.

[0048] Furthermore, attenuators, waveplates, dispersive elements, or nonlinear crystals can be added to both the fixed and delayed optical arms to achieve independent control of laser parameters such as energy, polarization, pulse width, and wavelength of the two laser beams. It is worth noting that it is preferable to add symmetrical optical elements to both the fixed and delayed optical arms to avoid affecting the zero-delay point. To ensure the accuracy of the dual-pulse delay parameters, a recalibration operation is required after adding symmetrical optical elements to both the fixed and delayed optical arms.

[0049] The dual-pulse sequence generated by the time-domain shaping module is further input to the autocorrelation calibration module. In the autocorrelation calibration module, based on the principle of intensity autocorrelation of the second harmonic generation (SHG), the zero-point of the inter-pulse delay and the measurement of the laser pulse width are achieved. In this embodiment, the dual-pulse sequence generated by the time-domain shaping module enters the autocorrelation calibration module 003 after passing through the third reflecting mirror 301.

[0050] The autocorrelation calibration module is a coaxial optical path system, including a type II phase-matched nonlinear crystal 302, a low-pass filter 303, a convex lens 304, and a detector 305. The type II phase-matched nonlinear crystal (selectively made of BBO, KTP, or LBO) converts the double pulse into an SHG signal. By adjusting the incident angle θ and azimuth angle φ of the crystal, the phase-matching condition is met, avoiding interference effects. The low-pass filter 303 filters out residual fundamental frequency light, retaining the harmonic SHG signal. The convex lens 304 focuses the SHG signal onto the detector. The detector 305 can be a photodiode detector or a fiber optic spectrometer, used to acquire the SHG signal intensity.

[0051] It should be noted that Type II phase matching utilizes the summation of the fundamental frequency laser light of the ordinary (o) and extraordinary (e) light to generate a frequency-doubled e-light. In Type II phase matching, since the polarization states of the two coaxial laser pulses are orthogonal, they do not interfere. Conversely, if the polarization states of the two laser pulses are parallel, interference will occur, yielding an interference autocorrelation result. Interference autocorrelation is complex and not intuitive for laser pulse width measurement, causing inconvenience in practical applications.

[0052] Given the laser wavelength, the phase matching angle of the nonlinear crystal can be determined based on the phase matching condition Δk = 0.

[0053] Then we have:

[0054]

[0055] In the formula, k e (2ω) is the frequency harmonic wave vector, k e (ω) is the original frequency e light wave vector, k o(ω) is the wave vector of the original frequency θ. The type II phase matching angle can be obtained using the graphical method of the refractive index ellipsoid, thus allowing for the customization of the nonlinear crystal. However, due to crystal processing errors or deviations in laser wavelength, the nonlinear crystal often cannot precisely achieve the aforementioned phase matching condition when incident perpendicularly. Therefore, it is usually necessary to adjust the angles of the nonlinear crystal in two directions to satisfy the type II SHG phase matching. Firstly, the incident angle θ is adjusted to compensate for the phase matching angle; secondly, the azimuth angle φ of the optical axis is adjusted to make the optical axis parallel or perpendicular to the laser polarization.

[0056] Based on the principle of intensity autocorrelation, scanning the extension line can acquire the time-domain curve of SHG intensity autocorrelation, where the position x0 of the peak point is the desired zero-delay point.

[0057] Furthermore, by subtracting the bias of x0, the displacement coordinate x of the delay line can be converted into the delay amount Δt, which is expressed by the following formula:

[0058]

[0059] Thus, the intensity autocorrelation plot as a function of time Δt is obtained.

[0060] Full width at half maximum (FWHM) of the autocorrelation function FWHM The pulse width τ of the original time-domain function is not equal to that of the pulse pulse in the original time-domain function, but rather there is a proportional relationship between them. For example, for a Gaussian distributed laser pulse, its time-domain pulse width is τ = τ FWHM / 1.414; for sech 2 The laser pulse has a time-domain pulse width of τ = τ FWHM / 1.543. Ideal ultrafast lasers are typically sech... 2 Given the time-domain distribution, a scaling factor of 1.543 is chosen, i.e., τ = τ FWHM / 1.543.

[0061] Based on the above steps, the intensity autocorrelation curve can be obtained, and the offset zero point x0 of the delay and the pulse width τ of the super-optical laser can be obtained, thus completing the calibration of the time-domain shaping module.

[0062] The output of the aforementioned time-domain shaping module is coupled to both the laser processing platform and the autocorrelation calibration module, forming a calibration feedback mechanism. The delay zero point x0 and pulse width τ measured by the autocorrelation calibration module are fed back to the time-domain shaping module to correct the delay parameters and ensure system accuracy.

[0063] In fact, the time-shaping module and autocorrelation calibration module of this invention can be integrated onto an optical breadboard 004, such as... Figure 4 As shown, with Figure 2 The positions correspond to those shown in the optical path schematic diagram.

[0064] The working process of the above device is as follows:

[0065] First, the polarization states of the two laser pulses are adjusted to make them perpendicular to each other. For example, the first half-wave plate 102 is adjusted to make the first laser pulse P-polarized; the second half-wave plate 204 is adjusted to make the second laser pulse S-polarized, and they are coupled to the same optical axis through the second beam splitter 002 to form a double pulse. Here, the nonlinear crystal in the correlation calibration module is preferably a BBO crystal, and the fundamental laser wavelength is known to be 1040 nm, thus the type II phase matching angle of the BBO crystal is calculated to be 32.4°. Due to crystal processing errors and laser wavelength deviations, the phase matching angle needs to be adjusted according to the actual situation. For example, by adjusting the incident angle θ and azimuth angle φ of the nonlinear crystal to maximize the SHG light intensity, the actual phase matching conditions can be met, such as... Figure 3 As shown.

[0066] Next, a dual-pulse incident on the nonlinear crystal 302 is used, and the near-infrared fundamental frequency light is converted into frequency-doubled green light, generating an SHG signal, with some residual near-infrared light. Figure 3 In the diagram, the solid line represents residual near-infrared light 306, while the dashed line represents frequency-doubled green light 307. For clarity, the solid and dashed lines are displayed offset. After passing through a low-pass filter, the residual near-infrared light 306 is absorbed, leaving only the frequency-doubled green light 307. The light is then focused by a convex lens and sampled by detector 305. By changing the double-pulse time delay Δt using the optical delay line in the scanning time-domain shaping module, the SHG signal intensity at different time intervals can be acquired, and the intensity autocorrelation plot can be measured. Alternatively, a spectrometer can be selected as the detector.

[0067] In this embodiment, a fiber optic spectrometer is used as the detector, such as... Figure 4 As shown, the near-infrared laser light, after passing through a nonlinear crystal, is frequency-doubled and focused onto a fiber optic coupler. This coupler is mounted on a three-dimensional adjustable mechanism composed of a two-dimensional fine-tuning mirror mount 308 and a single-axis slide 309, used for adjusting the focal position. The optical signal finally enters the spectrometer 305 via a multimode fiber 310. By scanning the delay line 203, a two-dimensional FROG trajectory map is acquired, as shown below. Figure 5 As shown in (a) of the diagram. Taking the one-dimensional intensity data of the SHG signal with a center wavelength λ = 520.85 nm, an intensity autocorrelation diagram can be obtained. The peak point coordinate x0 of the intensity autocorrelation diagram is the position where the first and second laser pulse times coincide, i.e., the zero-delay point x0. From equation (3), the distance parameter of the x-axis can be converted into a time parameter, thus obtaining the FROG two-dimensional trajectory diagram and intensity autocorrelation diagram with the delay amount Δt as the x-axis, as shown in equation (3). Figure 5 As shown in (b) of the diagram.

[0068] If a photodiode is used as a detector, the intensity autocorrelation map can be obtained directly.

[0069] In this embodiment, the ultrafast laser's pulse width can be varied, with an adjustable range of 300-4300 fs. To test the feasibility of autocorrelation calibration, several sets of different pulse width parameters were tested, and the results are shown in Table 1 below:

[0070] Table 1 Pulse width test results

[0071]

[0072] The data in Table 1 confirms that the present invention can accurately measure the pulse width of ultrafast lasers and the time zero point of a double-pulse laser sequence, with a relative error of better than 3% in pulse width measurement. Since pulse width adjustment changes the time-domain waveform of the laser, causing the time origin to drift, the time delay zero point of the double pulse will also drift. Therefore, the present invention is particularly suitable for ultrafast laser systems with adjustable pulse width.

[0073] The above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. An ultrafast laser time-domain shaping and calibration device, characterized in that, include: Time-domain shaping module: used to split linearly polarized ultrafast laser beams into fixed optical arms and delayed optical arms, adjust the time delay of the dual pulses through optical delay lines, and independently control the laser parameters of the two optical arms, wherein the polarization states of the laser pulses of the two optical arms are orthogonal to each other; Autocorrelation calibration module: directly connected to the optical output of the time-domain shaping module via a coaxial optical path, and receives the double pulse sequence generated by the time-domain shaping module; The autocorrelation calibration module includes a type II phase-matched nonlinear crystal (302) for converting the received double pulses into SHG signals; the time delay of the double pulses is changed by scanning the optical delay line in the time-domain shaping module to acquire the SHG signal intensity under different timings. An intensity autocorrelation curve is generated based on the intensity distribution of the acquired SHG signal, the zero-delay point is calibrated, and the pulse width is calculated. The output of the time-domain shaping module is coupled to the laser processing platform and the autocorrelation calibration module to form a calibration feedback mechanism. The parameters measured by the autocorrelation calibration module are fed back to the time-domain shaping module to correct the delay parameters.

2. The ultrafast laser time-domain shaping and calibration device according to claim 1, characterized in that, The time-domain shaping module includes: First beam splitter (001): used to split the incident ultrafast laser beam into a first laser pulse and a second laser pulse, which enter the fixed optical arm and the delayed optical arm respectively; Fixed optical arm: Receives the first laser pulse from the first beam splitter (001) and is used to guide the propagation direction of the first laser pulse and regulate the polarization state of the first laser pulse; Delayed optical arm: Receives the second laser pulse from the first beam splitter (001), and is used to guide the propagation direction of the second laser pulse and adjust the polarization state and the amount of time delay of the double pulse; The second beam splitter (002) is used to combine two laser pulses returning from the fixed optical arm and the delayed optical arm respectively, outputting a coaxial ultrafast laser double pulse sequence, which is then directed to the autocorrelation calibration module and the laser processing platform respectively.

3. The ultrafast laser time-domain shaping and calibration device according to claim 1, characterized in that, The optical path of the fixed optical arm includes a first pair of mirrors (101), a first half-wave plate (102), and a first mirror (103). The first pair of mirrors (101) serves as the optical path entrance, receiving the first laser pulse after it is split from the first beam splitter (001) and guiding the optical path. The first half-wave plate (102) modulates the polarization state of the first laser pulse to form a P-polarization state. The first mirror (103) guides the polarization-modulated first laser pulse to the beam combining interface of the second beam splitter (002).

4. The ultrafast laser time-domain shaping and calibration device according to claim 1, characterized in that, The optical path of the delay arm includes a second mirror (201), a pair of second mirrors (202), an optical delay line (203), and a second half-wave plate (204) in sequence. The second mirror (201) serves as the optical path entrance, receiving the second laser pulse after it is split from the first beam splitter (001) and guiding the optical path. The second mirror pair (202) is installed on the optical delay line (203) and changes the optical path length of the second laser pulse by linear displacement, thereby changing the time delay of the double pulse. The second half-wave plate (204) is located between the optical delay line (203) and the beam combining interface of the second beam splitter (002) and modulates the polarization state of the second laser pulse to form an S-polarization state orthogonal to the first laser pulse.

5. The ultrafast laser time-domain shaping and calibration device according to claim 4, characterized in that, The optical delay line (203) is a single-axis linear electric slide, and the time delay of the double pulse is adjusted by controlling the displacement of the slide.

6. The ultrafast laser time-domain shaping and calibration device according to claim 1, characterized in that, The autocorrelation calibration module also includes a low-pass filter (303), a convex lens (304), and a detector (305). The low-pass filter (303) is used to filter out residual fundamental frequency light and retain the SHG signal of the harmonics. The convex lens (304) is used to focus the SHG signal onto the photosensitive surface of the detector (305) and the detector (305) collects the SHG signal intensity.

7. The ultrafast laser time-domain shaping and calibration device according to claim 1, characterized in that, The calibration of the zero-delay point and calculation of the pulse width include: Scan the intensity autocorrelation curve and identify the peak point position x0 of the curve as the zero delay point; The optical delay line displacement coordinate x is converted into the double pulse time delay Δt according to the formula Δt=(2x / c)-x0, where c is the speed of light; The actual laser pulse width is calculated based on the proportional relationship between the pulse width and the full width at half maximum (FWHM) of the autocorrelation curve of intensity.

8. The ultrafast laser time-domain shaping and calibration device according to claim 1, characterized in that, It also includes an optical breadboard, a time-domain shaping module, and an autocorrelation calibration module, all integrated on the optical breadboard to form a unified structure.

9. The ultrafast laser time-domain shaping and calibration device according to claim 1, characterized in that, The type II phase-matching nonlinear crystal is a BBO, KTP, or LBO crystal. The incident angle θ and azimuth angle φ of the nonlinear crystal are adjustable to meet the phase-matching conditions.

10. A time-domain shaping ultrafast laser system, characterized in that, include: Ultrafast lasers are used to generate linearly polarized and pulse-width-tunable ultrafast lasers. The ultrafast laser time-domain shaping and calibration apparatus as described in any one of claims 1 to 9 has its input terminal receiving the laser output from the ultrafast laser; The laser processing platform is coupled to the output of the ultrafast laser time-domain shaping and calibration device, and is used to receive the time-domain shaped laser for processing.

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