Ultrafast imaging and real-time processing integrated system based on spatial light modulator

Abstract

This invention belongs to the field of ultrafast laser application technology, specifically disclosing an integrated system for ultrafast imaging and real-time processing based on a spatial light modulator. The system includes a signal generator, a femtosecond laser, a first pump beam splitter, a probe light processing subsystem, a pump light modulation subsystem, a 4F unit, an optical delay translation stage, a fourth mirror, a second bandpass filter, a CCD camera, a coaxial cage-type mechanical module, a three-dimensional displacement stage, and a computer control subsystem. It utilizes a spatial light modulator to spatially shape the femtosecond laser, enabling simultaneous observation of transient material processes and precise shaping. This invention solves the problem of existing technologies being unable to seamlessly integrate traditional oblique-incident ultrafast pump-probe systems with diverse optical field processing capabilities in space and time.

Description

Technical Field

[0001] This invention belongs to the field of ultrafast laser application technology, specifically relating to an integrated system for ultrafast imaging and real-time processing based on a spatial light modulator. Background Technology

[0002] Femtosecond lasers are characterized by their extremely short pulse widths (typically 10^6 Hz). -13 -10 -15 With its extremely high peak power, femtosecond lasers have found wide applications in materials microfabrication and ultrafast dynamics research. Extremely short pulse widths can deposit energy into the electronic systems of materials within extremely short timescales, inducing non-thermal processes, transient ionization, and phase transitions, thereby enabling high-precision micro / nanofabrication with a low heat-affected zone and direct observation of transient material properties. In microfabrication, femtosecond lasers can achieve "cold processing," offering high precision and a small heat-affected zone; in ultrafast observation, ultrafast pump-probe imaging technology is an important tool for studying the interaction between lasers and materials.

[0003] However, traditional oblique-incidence ultrafast pump-probe systems suffer from focal point shift due to refraction of the pump light at the interface, causing the laser beam to deflect when focused on the interface material. Furthermore, laser processing systems typically have a fixed excitation field, making these two systems independently configured. This severely limits experimental flexibility, hindering the study of transient mechanisms in diverse optical fields and the processing requirements of interface materials. For example, in investigating plasma evolution mechanisms at the interface between transparent media and alloy welds under different pump light shapes, the focal point shifts at the interface with traditional oblique-incidence pump light, necessitating spatial overlap of the probe and pump beams to observe plasma evolution. Moreover, the oblique-incidence optical path framework is incompatible with the shaping processing system; a separate design requires two independent laser sources and optical path systems, resulting in high construction costs. Therefore, seamless spatiotemporal integration of traditional oblique-incidence ultrafast pump-probe systems with diverse optical field processing capabilities remains a significant challenge. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that existing technologies cannot seamlessly integrate traditional oblique-incident ultrafast pump detection systems with diverse optical field processing functions in space and time. This invention proposes an integrated system for ultrafast imaging and real-time processing based on a spatial light modulator.

[0005] The technical solution of the present invention is: an integrated system for ultrafast imaging and real-time processing based on a spatial light modulator, comprising a signal generator, a femtosecond laser, a first pump beam splitter, a probe light processing subsystem, a pump light modulation subsystem, a 4F unit, an optical delay translation stage, a fourth reflector, a second bandpass filter, a CCD camera, a coaxial cage mechanical module, a three-dimensional displacement stage, and a computer control subsystem;

[0006] A signal generator is used to trigger the femtosecond laser;

[0007] Femtosecond lasers are used to generate femtosecond laser pulses;

[0008] The first pump beam splitter is set at a 135° angle to the horizontal plane to split the femtosecond laser pulse into pump beam and probe beam.

[0009] The probe light processing subsystem is used to perform frequency domain shaping on the probe light;

[0010] The pump light modulation subsystem is used to modulate the pump light;

[0011] The 4F unit is built into a coaxial cage-type mechanical module and is used to transport the modulated pump light;

[0012] An optical delay translation stage is placed in the optical path of the probe light to adjust the time delay of the probe light reaching the sample;

[0013] The fourth reflector is set at a 135° angle to the horizontal plane and is used to reflect the probe light delayed by the optical delay translation stage to the coaxial cage mechanical module.

[0014] A coaxial cage-type mechanical module is used to coaxially combine and focus the modulated pump light, the processed probe light, and the illumination light onto the sample;

[0015] The second bandpass filter is used to filter out the non-probe laser beam scattered by the sample surface after the pump light excites the sample to obtain a pure probe light signal;

[0016] A CCD camera is used to receive the probe light or illumination light reflected from the surface of the sample to be tested and to acquire image information.

[0017] A three-dimensional displacement stage is used to place the sample to be tested;

[0018] The computer control subsystem is used to control the operation mode switching, parameter setting, and image data processing of the integrated system for ultrafast imaging and real-time processing based on spatial light modulators.

[0019] Preferably, the probe light processing subsystem includes a frequency doubling crystal, a first bandpass filter, a first mechanical switch, and a first reflector; the frequency doubling crystal, the first bandpass filter, the first mechanical switch, and the first reflector are sequentially arranged on the same horizontal straight optical path; the first reflector is set at a 45° angle to the horizontal plane, reflecting the probe light that has passed through the frequency doubling crystal, the first bandpass filter, and the first mechanical switch sequentially to the optical delay translation stage.

[0020] Preferably, the pump light modulation subsystem includes a half-wave plate, a polarizer, and a spatial shaping module; the half-wave plate and the polarizer are sequentially arranged on the same vertical straight optical path;

[0021] Half-wave plates and polarizers are used to adjust the pump light power;

[0022] The spatial shaping module is used to receive pump light with adjusted power and perform beam splitting control and modulation.

[0023] Preferably, the spatial shaping module includes a second pump beam splitter, a second mechanical switch, a fifth reflector, a third mechanical switch, and a spatial light modulator.

[0024] The second pump beam splitter is used to split the pump beam after the polarization direction is adjusted to obtain the first optical path and the second optical path. The first optical path is equipped with a second mechanical switch and a fifth reflector to realize the processing of the original Gaussian light field. The second optical path is equipped with a third mechanical switch and a spatial light modulator to perform programmable wavefront modulation on the pump beam to realize beam shaping.

[0025] Preferably, the 4F unit includes a third focusing lens and a fourth focusing lens disposed on the same horizontal straight optical path.

[0026] Preferably, the optical delay translation stage includes a second mirror and a third mirror disposed on the same horizontal straight optical path; the second mirror is disposed parallel to the first mirror and located on the same vertical straight optical path, and the third mirror is disposed at a 135° angle to the horizontal plane.

[0027] Preferably, the coaxial cage-type mechanical module also includes a first focusing lens, a probe beam splitter, a dichroic mirror, a focusing objective, a second focusing lens, a white light beam splitter, and an LED white light lamp; the first focusing lens and the probe beam splitter are located on the same horizontal straight optical path, and the LED white light lamp, white light beam splitter, second focusing lens, probe beam splitter, dichroic mirror, and focusing objective are sequentially arranged on the same vertical straight optical path, the white light beam splitter is set at a 45° angle to the horizontal plane, and the probe beam splitter and dichroic mirror are set at 135° angles to the horizontal plane respectively.

[0028] Preferably, the system includes both ultrafast imaging and real-time processing modes.

[0029] As a preferred method, the ultrafast imaging mode specifically includes the following steps:

[0030] The parameters of the integrated system for ultrafast imaging and real-time processing of spatial light modulators are set through a computer control subsystem.

[0031] The femtosecond laser is triggered by a signal generator to output a 1030nm femtosecond laser pulse, which is then divided into pump light and probe light, while keeping the first mechanical switch in the probe light processing subsystem constantly open.

[0032] The direction of the pump light is modulated, and the pump light is transported to the focusing objective in the coaxial cage mechanical module using the 4F unit. Then, the focusing objective is used to focus the pump light onto the surface or interface of the sample to be measured on the three-dimensional displacement stage.

[0033] Adjust the energy of the pump light to obtain the laser pulse energy to excite the sample under test, and control the movement of the optical delay translation stage to find the zero point of the time of the pump light and the probe light, so that the pump light and the probe light arrive at the surface or interface of the sample under test at the same time.

[0034] Based on the position of the zero point in time, the optical delay translation stage is moved to increase the optical path difference between the probe light and the pump light;

[0035] Probe light imaging was performed before and after the sample was excited by pump light, and differential processing was performed on the probe light images before and after the sample was excited by pump light to obtain the relative reflectance image, thus completing the ultrafast imaging of the sample.

[0036] As a preferred option, real-time processing specifically includes the following steps:

[0037] The parameters of the integrated system for ultrafast imaging and real-time processing of spatial light modulators are set through a computer control subsystem.

[0038] The signal generator triggers the femtosecond laser to output a 1030nm femtosecond laser pulse, which is then split into pump light and probe light. The first mechanical switch in the probe light processing subsystem is kept off, and the LED white light is turned on for illumination.

[0039] The direction of the pump light is modulated, and the pump light is transported to the focusing objective in the coaxial cage mechanical module using the 4F unit;

[0040] Adjusting the energy of the pump light to obtain laser pulse energy to excite the sample under test, thus initiating the processing task.

[0041] The beneficial effects of this invention are:

[0042] This invention utilizes the femtosecond pulse output from a femtosecond laser, splitting it into pump light and probe light. The pump light is split into a raw Gaussian beam and a spatial light modulator-shaped beam, with mechanical switches controlling their on / off states. The pump light is then introduced into a coaxial cage-type mechanical module, where a 4F unit composed of two focusing lenses transports the pump light to the focusing objective for excitation of the sample surface or interface. In ultrafast imaging mode, the probe light serves as illumination light. After passing through an optical delay translation stage, the probe light is introduced into the coaxial cage-type mechanical module to observe the changes in the sample surface or interface induced by the shaped pump light under different delay times. The reflected optical information is received by a CCD camera. In real-time processing mode, an LED white light serves as illumination light to monitor the processing effect of the pump light in real time for immediate feedback. This invention integrates pump-probe imaging and programmable micromachining into a single cage platform. Compared to separate systems, this reduces costs and simplifies alignment and maintenance. The spatial light modulator in the spatial shaping module enables arbitrary programmable shaping of the pump light, supporting special light field studies and significantly expanding experimental flexibility. During coaxial imaging, frequency doubling and bandpass filtering support multi-wavelength extended detection to avoid interference from pump-excited plasma. Real-time white light monitoring provides immediate feedback for the fabrication process. The cage layout and modular devices facilitate future expansion (such as introducing pump light temporal shaping devices, polarization control, more detection channels, or high frame rate cameras). Attached Figure Description

[0043] Figure 1 The diagram shows a block diagram of an integrated system for ultrafast imaging and real-time processing based on a spatial light modulator.

[0044] Figure 2 The image shown is a transient imaging experimental image and a processed morphology image (taking a gold film as an example) under the excitation of a shaping light field in an ultrafast imaging and real-time processing integrated system based on a spatial light modulator.

[0045] Figure 3 The image shown is an experimental image of the Invar alloy surface under coaxial pump light excitation by an integrated system of ultrafast imaging and real-time processing based on a spatial light modulator.

[0046] Figure 4 The image shown is an experimental image of transient imaging of the sapphire-Invar alloy interface using an integrated system of ultrafast imaging and real-time processing based on a spatial light modulator.

[0047] Figure 5 The diagram shows the flowchart of the ultrafast imaging mode.

[0048] Figure 6 The flowchart shown is for the real-time processing mode.

[0049] Figure descriptions: 1-Femtosecond laser, 2-First pump beam splitter, 3-Frequency doubling crystal, 4-First bandpass filter, 5-First mechanical switch, 6-First reflecting mirror, 7-Optical delay translation stage, 8-Second reflecting mirror, 9-Third reflecting mirror, 10-Fourth reflecting mirror, 11-First focusing lens, 12-Probe beam splitter, 13-Dichroic mirror, 14-Focusing objective lens, 15-Three-dimensional displacement stage, 16-Second focusing lens, 17-White light beam splitter, 18-L 19-Second bandpass filter, 20-CCD camera, 21-Half-wave plate, 22-Polarizer, 23-Second pump beam splitter, 24-Second mechanical switch, 25-Fifth reflector, 26-Third mechanical switch, 27-Spatial light modulator, 28-Spatial shaping module, 29-Third focusing lens, 30-Fourth focusing lens, 31-4F unit, 32-Coaxial cage mechanical module, 33-Signal generator, 34-Computer control subsystem. Detailed Implementation

[0050] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the invention, and are not intended to limit the scope of the invention.

[0051] Example 1:

[0052] like Figure 1 As shown, an integrated system for ultrafast imaging and real-time processing based on a spatial light modulator includes a signal generator 33, a femtosecond laser 1, a first pump beam splitter 2, a probe light processing subsystem, a pump light modulation subsystem, a 4F unit 31, an optical delay translation stage 7, a fourth mirror 10, a second bandpass filter 19, a CCD camera 20, a coaxial cage mechanical module 32, a three-dimensional displacement stage 15, and a computer control subsystem 34.

[0053] Signal generator 33 is used to trigger femtosecond laser 1;

[0054] Femtosecond laser 1 is used to generate femtosecond laser pulses. Typical parameters of femtosecond laser 1 include a center wavelength of approximately 1030 nm, a pulse width of less than 300 fs, and the ability to provide single high-energy pulses and repetition rates controlled by a computer control subsystem 34. However, these parameters are not limited to these specific parameters and can be selected according to the actual application. Femtosecond laser 1 can provide high-energy femtosecond laser pulses, and the repetition rate and energy of the pulse output can be actively controlled by the computer control subsystem 34.

[0055] The first pump beam splitter 2 is positioned at a 135° angle to the horizontal plane to split the femtosecond laser pulse into a pump beam and a probe beam. The first pump beam splitter 2 is a non-polarizing beam splitter, with a splitting ratio of 4:1 between the pump and probe beams. The femtosecond laser pulse beam output from the femtosecond laser 1, after passing through the first pump beam splitter 2, will obtain a pump beam carrying 4 / 5 of the energy and a probe beam carrying 1 / 5 of the energy. This ensures that the pump beam can ablate and process the surface or interface of the sample, and that the probe beam has sufficient energy for imaging without damaging the objective lens due to focusing by the focusing lens.

[0056] The probe light processing subsystem is used to perform frequency domain shaping on the probe light;

[0057] The pump light modulation subsystem employs a compact optical framework similar to the Michelson interferometer to modulate the pump light;

[0058] 4F unit 31 is built into coaxial cage mechanical module 32 and is used to transport the modulated pump light;

[0059] The optical delay translation stage 7 is set in the optical path of the probe light to adjust the time delay of the probe light reaching the sample;

[0060] The fourth reflector 10 is set at a 135° angle to the horizontal plane and is used to reflect the probe light delayed by the optical delay translation stage 7 to the coaxial cage mechanical module 32.

[0061] The coaxial cage mechanical module 32 is used to coaxially combine the modulated pump light, the processed probe light and the illumination light and focus them onto the sample.

[0062] The second bandpass filter 19 is used to filter out the non-probe laser beam scattered by the sample surface after the pump light excites the sample to obtain a pure probe light signal.

[0063] CCD camera 20 is used to receive probe light or illumination light reflected from the surface of the sample to be tested and to acquire image information;

[0064] The three-dimensional displacement stage 15 is used to place the sample to be tested.

[0065] The computer control subsystem 34 is used to control the operation mode switching, parameter setting, and image data processing of the integrated system for ultrafast imaging and real-time processing based on spatial light modulator.

[0066] In this embodiment, the probe light processing subsystem includes a frequency doubling crystal 3, a first bandpass filter 4, a first mechanical switch 5, and a first reflector 6; the frequency doubling crystal 3, the first bandpass filter 4, the first mechanical switch 5, and the first reflector 6 are sequentially arranged on the same horizontal straight optical path; the first reflector 6 is arranged at a 45° angle to the horizontal plane, reflecting the probe light that has passed through the frequency doubling crystal 3, the first bandpass filter 4, and the first mechanical switch 5 sequentially to the optical delay translation stage 7.

[0067] In this embodiment, the pump light modulation subsystem employs a compact optical framework similar to a Michelson interferometer. The pump light is split into two Gaussian beams by a beam splitter, and their on / off states are controlled separately by mechanical switches, thereby generating the original Gaussian light field and the wavefront-shaped light field of the spatial light modulator. The pulse beam is defined as the pump light. The pump light modulation subsystem includes a half-wave plate 21, a polarizer 22, and a spatial shaping module 28; the half-wave plate 21 and the polarizer 22 are sequentially arranged on the same vertical straight optical path.

[0068] Half-wave plate 21 and polarizer 22 are used to adjust the pump light power; half-wave plate 21 changes the polarization of the laser, i.e., the pump light, and polarizer fixes the polarization direction of the laser output. Thus, the laser power is adjusted by rotating half-wave plate 21 through half-wave plate 21 and polarizer 22.

[0069] Spatial shaping module 28 is used to receive pump light with adjusted power and perform beam splitting control and modulation.

[0070] In this embodiment, the spatial shaping module 28 includes a second pump beam splitter 23, a second mechanical switch 24, a fifth reflector 25, a third mechanical switch 26, and a spatial light modulator 27.

[0071] The second pump beam splitter 23 is used to split the pump beam after the polarization direction is adjusted to obtain the first optical path and the second optical path. The first optical path is provided with a second mechanical switch 24 and a fifth reflector 25 to realize the processing of the original Gaussian light field. The second optical path is provided with a third mechanical switch 26 and a spatial light modulator 27 to perform programmable wavefront modulation on the pump beam to realize beam shaping. The modulation modes include, but are not limited to: square, flat-top, vortex, polygonal and multi-point light field, etc.

[0072] The second pump beam splitter 23 is a non-polarizing beam splitter, with a splitting ratio of 1:1 for the two pump beams. The compact optical frame of the Michelson interferometer integrates the processing modes of the ordinary Gaussian light field and the processing modes of the spatial light modulator-shaped light field, saving space utilization and enabling active control through mechanical switches.

[0073] The spatial light modulator 27 can shape the original Gaussian beam into light field distributions of different spatial shapes to support the study of special light field action mechanisms in transient imaging and processing. Furthermore, the pump light shaped by the spatial light modulator can be focused independently of the probe light through a coaxial system. In imaging mode, it does not interfere with the imaging quality of the probe light and does not change the spatial distribution of the probe light.

[0074] In this embodiment, the 4F unit 31 includes a third focusing lens 29 and a fourth focusing lens 30 disposed on the same horizontal straight optical path.

[0075] In this embodiment, the optical delay translation stage 7 includes a second mirror 8 and a third mirror 9 disposed on the same horizontal straight optical path; the second mirror 8 is disposed parallel to the first mirror 6 and located on the same vertical straight optical path, and the third mirror 9 is disposed at a 135° angle to the horizontal plane.

[0076] In this embodiment, the coaxial cage-type mechanical module 32 further includes a first focusing lens 11, a probe beam splitter 12, a dichroic mirror 13, a focusing objective lens 14, a second focusing lens 16, a white light beam splitter 17, and an LED white light lamp 18. The first focusing lens 11 and the probe beam splitter 12 are located on the same horizontal straight optical path. The LED white light lamp 18, the white light beam splitter 17, the second focusing lens 16, the probe beam splitter 12, the dichroic mirror 13, and the focusing objective lens 14 are sequentially arranged on the same vertical straight optical path. The white light beam splitter 17 is set at a 45° angle to the horizontal plane, and the probe beam splitter 12 and the dichroic mirror 13 are set at a 135° angle to the horizontal plane, respectively.

[0077] The computer control subsystem 34 sends commands to the signal generator 33 to trigger the generation of a high-energy single pulse from the femtosecond laser 1. Two apertures are used to collimate the laser beam, ensuring it propagates along the straight line formed by the two apertures. A beam splitter separates the light pulse into pump and probe beams. A half-wave plate 21 and a polarizer 22 are used to adjust the energy and polarization direction of the pump beam to obtain the required pump beam energy. A compact optical framework similar to a Michelson interferometer is used to control the pump beam splitting, thus switching between the ordinary processing mode and the shaping processing mode. The pump beam is split into two arms by the pump beam splitter; one arm is shaped by the spatial light modulator 27, and the other arm is shaped by a fixed beam splitter. The fifth reflecting mirror 25 realizes the processing mode of the original Gaussian light field. The switching of the processing modes of the two arms is controlled by the opening and closing of two mechanical switches. The pump light field is transported by the optical transport optical path composed of two focusing lenses, and the transported light field is passed through the dichroic mirror 13 and the focusing objective lens 14 in sequence. The pump light is focused on the sample surface or interface placed on the three-dimensional displacement stage 15. The white light excited by the LED white light lamp 18 passes through the white light beam splitter 17, the first focusing lens 11, the probe light beam splitter 12 and the dichroic mirror 13 in sequence, and is focused on the sample surface by the focusing objective lens 14. After being reflected by the sample surface, it is folded back into the CCD camera 20 to realize white light illumination. The probe light is frequency-domain shaped by a frequency-doubling crystal 3 and a first bandpass filter 4 to obtain a probe light with a wavelength half that of the original wavelength. A mechanical switch controls the on / off state of the probe light path, and an optical delay translation stage 7 controls the delay time between the pump light and the probe light. The probe light is sequentially passed through a first focusing lens 11, a probe light beam splitter 12, and a dichroic mirror 13, and then focused onto the surface of the sample under test by a focusing objective lens 14. After vertical reflection from the sample surface, the light is refracted back into the CCD camera 20 to illuminate the sample. A coaxial cage-type mechanical module 32 keeps the pump light path, the probe light path, and the white light monitoring light path on the same axis. In the white light real-time monitoring mode, the CCD camera 20 monitors the processing under white light illumination in real time. In the ultrafast imaging mode, the CCD camera 20 captures and records the dynamic signal after the femtosecond laser 1 excites the surface or interface of the sample under test. The computer control subsystem 34 acquires the image information output by the CCD camera to obtain the ultrafast imaging information of the surface or interface of the sample under test.

[0078] Each mechanical switch, along with each reflector and the spatial light modulator 27, works in conjunction to switch between the original Gaussian light field mode and the spatial light modulator shaping mode. One of the two processing arms achieves the original Gaussian light field via a fixed reflector, while the other arm achieves the shaped light field via the spatial light modulator 27. The opening and closing of the mechanical switches are triggered by the computer control subsystem 34. The 4F unit 31, composed of two focusing lenses, completes the transport of the pump light. Even with the spatial light modulator 27 equipped with a blank phase, the pixel-level liquid crystal still causes a change in the light field distribution of the original Gaussian beam and a significant reduction in energy. Mode switching effectively prevents distortion of the original Gaussian beam's light field. The 4F unit 31 is compatible with both the original Gaussian beam and the shaped beam transport and does not affect beam propagation.

[0079] The probe light undergoes frequency-domain shaping or wavelength transformation via the frequency-doubling crystal 3 and the first bandpass filter 4 to obtain a probe light of a specific wavelength after frequency doubling, which is then used for reflective imaging. The frequency-domain shaped probe light is then subjected to delayed scanning by the optical delay translation stage 7 and a pump light with a fixed optical path difference. Simultaneously, images are acquired by the CCD camera 20, the signal generator 33, and the computer control subsystem 34. The computer control subsystem 34 includes software modules for generating the phase diagram of the spatial light modulator 27, synchronous trigger control, image acquisition, and real-time image processing. It can also adjust the phase diagram based on real-time image feedback to achieve closed-loop processing control. The frequency-doubling crystal 3 and the first bandpass filter 4 enable the rapid acquisition of a pure frequency-domain shaped beam, filtering out interference from the original wavelength for imaging. Since the CCD camera 20 can achieve relatively long exposure times, the computer control subsystem 34 sends a signal to trigger the signal generator 33 to generate a synchronization signal to control the mechanical switch, the optical delay translation stage 7, and the CCD camera 20, thereby achieving precise single-shot transient exposure imaging.

[0080] The probe light is superimposed on the coaxial cage-like mechanical module 32 via the first focusing lens 11, the probe light beam splitter 12, the dichroic mirror 13, and the focusing objective lens 14 to achieve transient imaging for studying the interaction process between laser and matter. Meanwhile, the white light illumination is superimposed on the coaxial cage-like mechanical module 32 via the white light beam splitter 17, the first focusing lens 11, the probe light beam splitter 12, the dichroic mirror 13, and the focusing objective lens 14 via the LED white light lamp 18 to achieve real-time white light monitoring for macroscopic alignment and process feedback during manufacturing. Integrating the ultrafast imaging system and the real-time white light monitoring system into the coaxial cage-like mechanical module 32 enables a coaxial modular layout and highly stable alignment of optical components, facilitating rapid system adjustment and maintenance, and reducing the cost of separate optical path construction.

[0081] The following components are sequentially installed on the optical platform: a French Amplitude femtosecond laser with a center wavelength of 1030 nm and a pulse width of 150 fs; a first pump beam splitter; a second pump beam splitter; a probe beam splitter; a frequency doubling crystal; a first bandpass filter; a first reflector; a second reflector; a third reflector; a fourth reflector; an optical delay translation stage; a first focusing lens; a second focusing lens; a third focusing lens; a fourth focusing lens; a focusing objective lens; a white light beam splitter; a three-dimensional displacement stage; an LED white light lamp; a CCD camera; a first mechanical switch; a second mechanical switch; a third mechanical switch; a coaxial cage mechanical module; a spatial light modulator; a signal generator; and a computer control subsystem. The computer control subsystem 34 sends commands to the signal generator 33 to trigger the generation of a high-energy single pulse of the femtosecond laser. Two apertures are used to collimate the laser beam, ensuring it propagates along the straight line formed by the two apertures. The first pump beam splitter 2 splits the light pulse into pump and probe beams. A half-wave plate 21 and a polarizer 22 are used to adjust the energy and polarization direction of the pump beam to obtain the required pump beam energy. A compact optical framework similar to a Michelson interferometer is used to control the pump beam splitting, thus switching between the ordinary processing mode and the shaping processing mode. The second pump beam splitter 23 splits the pump beam into two arms. One arm is shaped by a spatial light modulator 27, and the other arm is processed into the original Gaussian light field mode through a fixed fifth reflecting mirror 25. The opening and closing of the mechanical switches (24, 26) respectively control the switching of the processing modes of the two arms. The pump light, which determines the processing mode, is transported through the optical transport optical path composed of the third focusing lens 29 and the fourth focusing lens 30. The transported light field is then passed sequentially through the dichroic mirror 13 and the focusing objective lens 14 to focus the pump light onto the sample surface or interface placed on the three-dimensional displacement stage 15. The white light excited by the LED white light lamp 18 is passed sequentially through the white light beam splitter 17, the probe light beam splitter 12 and the dichroic mirror 13, and then focused onto the sample surface by the focusing objective lens 14. After being vertically reflected by the sample surface, the light returns along the same path and passes sequentially through the focusing objective lens 14, the dichroic mirror 13, the probe light beam splitter 12, the white light beam splitter 17, the second bandpass filter 19 and the CCD camera 20 to achieve white light illumination.The probe light is frequency-domain shaped by the frequency doubling crystal 3 and the first bandpass filter 4 to obtain a probe light with a wavelength half that of the original wavelength. The delay time between the pump light and the probe light is controlled by the optical delay translation stage 7. The probe light is sequentially passed through the first focusing lens 11, the probe light beam splitter 12 and the dichroic mirror 13, and then focused onto the surface of the sample under test by the focusing objective lens 14. After being reflected by the surface of the sample under test, it returns along the same path and sequentially passes through the focusing objective lens 14, the dichroic mirror 13, the probe light beam splitter 12, the white light beam splitter 17, the second bandpass filter 19 and the CCD camera 20 for probe light illumination.

[0082] This invention integrates an ultrafast pump-probe system with a laser spatial shaping real-time processing system through optical path design. This integrated design reduces the high cost of building separate systems and overcomes the limitations of traditional optical pump-probe systems due to fixed spatial light field excitation. By integrating the spatial light modulator 27 into the pump optical path, flexible control of the pump light field is achieved, enabling the execution of diverse excitation real-time processing modes and ultrafast imaging modes on the same platform. The system should be able to perform the following on the same platform: generation of programmable pump light fields (including square, flat-top, vortex, polygonal, and multi-spot light fields), precise delay control of pump-probe synchronization, frequency-domain shaping of probe light acquisition, and real-time processing monitoring and closed-loop control based on white light / short-wavelength detection.

[0083] In this embodiment, as Figure 2 The image shows transient imaging experimental images and processed morphology images (taking a gold film as an example) under the excitation of a shaping light field using the ultrafast imaging and real-time processing integrated system based on a spatial light modulator proposed in this invention. In the figure, 20μm and 10μm are dimension bars, and 20x and 50x are the magnifications of the observation objective lens. Figure 2 As shown, spatially shaped pump light excitation enables observation of the transient ablation process of the gold film within a 1000 ps delay time, allowing for the study of the ablation mechanism under different optical fields. The spatially shaped pump light simultaneously achieves array-like processing of the gold film, and images of different ablation shapes are shown below. Figure 3 As shown in the figure on the right.

[0084] In this embodiment, as Figure 3 and Figure 4 The image shown is a transient imaging experimental image of the Invar alloy surface and sapphire-Invar alloy interface under coaxial pump light excitation by the ultrafast imaging and real-time processing integrated system based on spatial light modulator proposed in this invention. Figure 3 As shown, the transient ablation process on the Invar alloy surface with a delay of 3200 ps can be observed using coaxial pump light excitation. Figure 4As shown, the transient ablation process at the sapphire-Invar alloy interface with a delay of 3200 ps can be observed using coaxial pump light excitation. Besides the differences in the observed transient ablation regions, the shock wave evolution on the surface and interface also exhibits significant mechanistic differences. Combined with... Figure 2 , Figure 3 and Figure 4 This indicates that the ultrafast imaging and real-time processing integrated system based on spatial light modulator proposed in this invention is applicable to multi-material systems.

[0085] In this embodiment, the system includes two modes: ultrafast imaging and real-time processing. Before operating the two modes, the optical path of the system is collimated to ensure that all beams are accurately collimated and propagated, to ensure that the three-dimensional displacement stage 15 is horizontal, and to ensure that the position of the beam does not change significantly when the optical delay translation stage 7 moves.

[0086] like Figure 5 As shown, the ultrafast imaging mode specifically includes the following steps:

[0087] S01. The parameters of the integrated system for ultrafast imaging and real-time processing of the spatial light modulator are set by the computer control subsystem 34. The parameter settings include the repetition frequency and energy of the femtosecond laser 1, the frequency and duty cycle of the signal generator 33, and the phase diagram of the spatial light modulator 27.

[0088] S02. The femtosecond laser 1 is triggered by the signal generator 33 to output a 1030nm femtosecond laser pulse, which is then divided into pump light and probe light. The first mechanical switch 5 in the probe light processing subsystem is kept open. The opening and closing of the first mechanical switch 5 is controlled by the computer control subsystem 34.

[0089] S03. Modulate the direction of the pump light, use the 4F unit 31 to transport the pump light to the focusing objective 14 in the coaxial cage mechanical module 32, and then use the focusing objective 14 to focus the pump light on the surface or interface of the sample to be tested on the three-dimensional displacement stage 15.

[0090] S04. Adjust the energy of the pump light to obtain the laser pulse energy to excite the sample under test, and control the optical delay translation stage 7 to move to find the zero point of the pump light and the probe light, so that the pump light and the probe light arrive at the surface or interface of the sample under test at the same time.

[0091] S05. Based on the position of the zero point of time, control the movement of the optical delay translation stage 7 to increase the optical path difference between the probe light and the pump light;

[0092] S06. Perform probe light imaging before and after pump light excitation of the sample under test, and perform differential processing on the probe light imaging before and after pump light excitation of the sample under test to obtain a relative reflectance image, thus completing the ultrafast imaging of the sample under test.

[0093] like Figure 6 As shown, real-time processing specifically includes the following steps:

[0094] S11. The parameters of the integrated system for ultrafast imaging and real-time processing of the spatial light modulator are set by the computer control subsystem 34;

[0095] S12. The femtosecond laser 1 is triggered by the signal generator 33 to output a 1030 nm femtosecond laser pulse, which is then split into pump light and probe light. The first mechanical switch 5 in the probe light processing subsystem is kept off, and the LED white light 18 is turned on for illumination.

[0096] S13. Modulate the direction of the pump light and use the 4F unit 31 to transport the pump light to the focusing objective lens 14 in the coaxial cage mechanical module 32;

[0097] S14. Adjust the energy of the pump light to obtain laser pulse energy to excite the sample under test and start the processing task.

[0098] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. An integrated system of ultrafast imaging and real-time processing based on a spatial light modulator, characterized in that, It includes a signal generator (33), a femtosecond laser (1), a first pump beam splitter (2), a probe light processing subsystem, a pump light modulation subsystem, a 4F unit (31), an optical delay translation stage (7), a fourth reflector (10), a second bandpass filter (19), a CCD camera (20), a coaxial cage mechanical module (32), a three-dimensional displacement stage (15), and a computer control subsystem (34). Signal generator (33) is used to trigger femtosecond laser (1); A femtosecond laser (1) is used to generate femtosecond laser pulses; The first pump beam splitter (2) is set at a 135° angle to the horizontal plane to split the femtosecond laser pulse into pump light and probe light; The probe light processing subsystem is used to perform frequency domain shaping on the probe light; The pump light modulation subsystem is used to modulate the pump light; The 4F unit (31) is built into the coaxial cage mechanical module (32) and is used to transport the modulated pump light; An optical delay translation stage (7) is set in the optical path of the probe light to adjust the time delay of the probe light reaching the sample; The fourth reflector (10) is set at a 135° angle to the horizontal plane and is used to reflect the probe light delayed by the optical delay translation stage (7) to the coaxial cage mechanical module (32). A coaxial cage mechanical module (32) is used to coaxially combine the modulated pump light, the processed probe light and the illumination light and focus them onto the sample. The second bandpass filter (19) is used to filter out the non-probe laser beam scattered by the sample surface after the pump light excites the sample to obtain a pure probe light signal. A CCD camera (20) is used to receive the probe light or illumination light reflected from the surface of the sample to be tested and to acquire image information; A three-dimensional displacement stage (15) is used to place the sample to be tested; The computer control subsystem (34) is used to control the operation mode switching, parameter setting and image data processing of the integrated system for ultrafast imaging and real-time processing based on spatial light modulator.

2. The spatial light modulator based integrated system of ultrafast imaging and real-time processing according to claim 1, wherein, The probe light processing subsystem includes a frequency doubling crystal (3), a first bandpass filter (4), a first mechanical switch (5), and a first reflector (6); the frequency doubling crystal (3), the first bandpass filter (4), the first mechanical switch (5), and the first reflector (6) are arranged sequentially on the same horizontal straight optical path; the first reflector (6) is set at a 45° angle to the horizontal plane, and reflects the probe light that passes through the frequency doubling crystal (3), the first bandpass filter (4), and the first mechanical switch (5) sequentially to the optical delay translation stage (7).

3. The integrated system for ultrafast imaging and real-time processing based on a spatial light modulator according to claim 1, characterized in that, The pump light modulation subsystem includes a half-wave plate (21), a polarizer (22), and a spatial shaping module (28); the half-wave plate (21) and the polarizer (22) are arranged sequentially on the same vertical straight optical path; A half-wave plate (21) and a polarizer (22) are used to adjust the pump light power; The spatial shaping module (28) is used to receive pump light with adjusted power and perform beam splitting control and modulation.

4. The spatial light modulator based integrated system of ultrafast imaging and real-time processing according to claim 3, wherein, The spatial shaping module (28) includes a second pump beam splitter (23), a second mechanical switch (24), a fifth reflector (25), a third mechanical switch (26), and a spatial light modulator (27). The second pump beam splitter (23) is used to split the pump beam after adjusting the polarization direction to obtain the first optical path and the second optical path. The first optical path is provided with a second mechanical switch (24) and a fifth reflector (25) to realize the processing of the original Gaussian light field. The second optical path is provided with a third mechanical switch (26) and a spatial light modulator (27) to perform programmable wavefront modulation on the pump beam to realize beam shaping.

5. The spatial light modulator based integrated ultrafast imaging and real-time processing system of claim 1, wherein, The 4F unit (31) includes a third focusing lens (29) and a fourth focusing lens (30) disposed on the same horizontal straight optical path.

6. The spatial light modulator based integrated ultrafast imaging and real-time processing system of claim 2, wherein, The optical delay translation stage (7) includes a second mirror (8) and a third mirror (9) set on the same horizontal straight optical path; the second mirror (8) is set parallel to the first mirror (6) and located on the same vertical straight optical path, and the third mirror (9) is set at an angle of 135° to the horizontal plane.

7. The spatial light modulator based integrated ultrafast imaging and real-time processing system of claim 1, wherein, The coaxial cage-type mechanical module (32) also includes a first focusing lens (11), a probe beam splitter (12), a dichroic mirror (13), a focusing objective (14), a second focusing lens (16), a white light beam splitter (17), and an LED white light lamp (18). The first focusing lens (11) and the probe beam splitter (12) are located on the same horizontal straight optical path. The LED white light lamp (18), the white light beam splitter (17), the second focusing lens (16), the probe beam splitter (12), the dichroic mirror (13), and the focusing objective (14) are arranged sequentially on the same vertical straight optical path. The white light beam splitter (17) is set at a 45° angle to the horizontal plane, and the probe beam splitter (12) and the dichroic mirror (13) are set at a 135° angle to the horizontal plane, respectively.

8. The integrated system for ultrafast imaging and real-time processing based on a spatial light modulator according to any one of claims 1-7, characterized in that, The system includes two modes: ultrafast imaging and real-time processing.

9. The spatial light modulator based integrated system of ultrafast imaging and real-time processing according to claim 8, wherein, The ultrafast imaging mode specifically includes the following steps: The parameters of the integrated system for ultrafast imaging and real-time processing of the spatial light modulator are set by the computer control subsystem (34); The femtosecond laser (1) is triggered by the signal generator (33) to output a 1030nm femtosecond laser pulse, which is then divided into pump light and probe light, and the first mechanical switch (5) in the probe light processing subsystem is kept open. The direction of the pump light is modulated, and the pump light is transported to the focusing objective (14) in the coaxial cage mechanical module (32) using the 4F unit (31). Then, the pump light is focused on the sample surface or interface of the three-dimensional displacement stage (15) using the focusing objective (14). Adjust the energy of the pump light to obtain the laser pulse energy to excite the sample to be tested, and control the movement of the optical delay translation stage (7) to find the zero point of the pump light and the probe light so that the pump light and the probe light arrive at the surface or interface of the sample to be tested at the same time. Based on the position of the zero point of time, control the movement of the optical delay translation stage (7) to increase the optical path difference between the probe light and the pump light; Probe light imaging was performed before and after the sample was excited by pump light, and differential processing was performed on the probe light images before and after the sample was excited by pump light to obtain the relative reflectance image, thus completing the ultrafast imaging of the sample.

10. The integrated system for ultrafast imaging and real-time processing based on a spatial light modulator according to claim 8, characterized in that, Real-time processing specifically includes the following steps: The parameters of the integrated system for ultrafast imaging and real-time processing of the spatial light modulator are set by the computer control subsystem (34); The signal generator (33) triggers the femtosecond laser (1) to output a 1030 nm femtosecond laser pulse, which is then divided into pump light and probe light. The first mechanical switch (5) in the probe light processing subsystem is kept off, and the LED white light (18) is turned on for illumination. The direction of the pump light is modulated, and the pump light is transported to the focusing objective (14) in the coaxial cage mechanical module (32) using the 4F unit (31); Adjusting the energy of the pump light to obtain laser pulse energy to excite the sample under test, thus initiating the processing task.

Images