CN115541560A - Laser time-frequency transformation observation system and method based on hyperspectral imaging - Google Patents

Abstract

The invention provides a laser time-frequency transformation observation system and method based on hyperspectral imaging. Chopper, white light crystal, beam reduction and expansion subsystem, beam homogenization and spot homogenization device, focusing lens, aperture, optical power meter, optical filter, optical delay translation stage, pulse shaping subsystem, samples Loading subsystem, hyperspectral camera shooting subsystem and computer control subsystem. The present invention uses a hyperspectral camera to replace the traditional CCD camera for optical imaging and spectral imaging of the instantaneous evolution state of the surface of the sample to be measured, making up for the limited observation ability caused by the influence of the optical diffraction limit in the traditional optical pumping detection technology. Real-time optical imaging and two-dimensional spectral imaging are performed on the surface of the sample to be tested.

Description

A laser time-frequency transformation observation system and method based on hyperspectral imaging

technical field

The invention belongs to the technical field of ultrafast laser observation, and in particular relates to a laser time-frequency transformation observation system and method based on hyperspectral imaging.

Background technique

As a nonlinear, non-equilibrium, multi-scale ultrafast process, femtosecond laser involves complex physical processes such as energy deposition, transfer, phase change and removal of the sample to be measured. Through experiments, the observation method with ultrafast time resolution is applied to reveal the interaction mechanism between femtosecond laser and matter, which is of great significance to the development of femtosecond laser processing field. At present, the observation methods used to study the interaction process between femtosecond laser and matter mainly include time-resolved optical imaging technology, time-resolved X-ray diffraction technology, time-resolved electron diffraction technology, time-resolved transient absorption spectroscopy, etc.

The basic idea of pump-probe technology is to study the transient evolution process by using two pulsed lasers whose time delay is carefully designed. The excitation region is observed after a certain time delay. At present, pump detection technology is used to study the transient process of femtosecond laser processing samples to be tested, mainly by means of signal receiving devices such as CCD charge-coupled devices and photodiodes, and the detection light under different detection delays can be obtained through different signal acquisition methods The light intensity and phase changes, so as to analyze the ultrafast evolution process of the transient properties of the sample to be tested after laser action. Due to the use of optical imaging, the traditional femtosecond laser optical pumping detection technology can only observe the instantaneous optical property changes induced by the surface of the sample to be tested. The analysis of ultrafast kinetic information mainly starts from the reflectivity and image structure. , the signal-to-noise ratio is low, the background difference caused by the fluctuation of the laser output is greatly affected, the content of the plasma, shock wave and phase change evolution that can be observed is limited, and limited by the optical diffraction limit, the spatial resolution of its detection is insufficient To detect the dynamic information of nanoscale electrons and lattices. However, the transient absorption spectroscopy detection technology derived from the pump detection technology can only detect a single point in the excited region of the sample to obtain a one-dimensional absorption spectrum, and it is impossible to directly observe the surface of the sample to be measured due to the weak optical signal. Due to the transient evolution process, the plasma eruption and shock wave propagation process on the surface of the sample to be tested cannot be observed, and the ability to observe the ablation of the sample to be tested is limited.

Hyperspectral imaging technology organically combines traditional two-dimensional imaging technology and spectral technology. It is a fine technology that can capture and analyze point-by-point spectra in a spatial area. Because it can detect the unique Spectral "signatures" so that visually indistinguishable substances can be detected. This technology has many advantages such as spatial recognizability, super multi-band, high spectral resolution, wide spectral range and map-spectrum integration. Spectral imaging is mainly used to measure the reflected light after the interaction between light and matter. Imaging technology can obtain the instantaneous optical property changes of the surface of the sample to be tested. Since the state of the surface of the sample at multiple time and space scales after being excited by ultrafast laser has different nonlinear non-equilibrium effects on imaging light sources at different wavelengths, the two-dimensional spectroscopy technology for imaging in multiple bands can be intuitively and comprehensively Characterize the characteristics of the plasma carrying the information of the sample elements and the energy transfer of the excited state of the molecule, and obtain the dynamic information of the molecule. The combination of hyperspectral imaging technology and optical pump detection technology can obtain more physical and chemical information and morphological information on the surface of the sample to be tested at an ultrafast scale, so as to gain a more comprehensive understanding of the ultrafast dynamics of femtosecond laser processing and explore.

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the present invention provides a laser time-frequency transformation observation system and method based on hyperspectral imaging. The present invention uses a hyperspectral camera to replace the traditional CCD camera for optical imaging of the instantaneous evolution state of the surface of the sample to be measured And spectral imaging, to make up for the limited observation ability caused by the influence of optical diffraction limit in traditional optical pump detection technology, to perform real-time optical imaging and two-dimensional spectral imaging on the surface of the sample to be measured excited by femtosecond laser.

In order to achieve the above object, the technical scheme adopted in the present invention is:

This solution provides a laser time-frequency conversion observation system based on hyperspectral imaging, including an optical platform and a femtosecond laser set on the optical platform, a pulse signal generator, a mirror, a beam splitter, a laser optical chopper, a white light Crystal, beam shrinking and expanding subsystem, beam homogenization and spot homogenization device, focusing lens, diaphragm, optical power meter, optical filter, optical delay translation stage, pulse shaping subsystem, sample loading subsystem, high Spectrum camera shooting subsystem and computer control subsystem;

The computer control subsystem issues instructions to the pulse signal generator to excite the femtosecond laser to output high-energy femtosecond pulses. The high-energy femtosecond pulses are divided into pump light and probe light by the beam splitter, and the laser path is controlled by the aperture. The collimation process makes it propagate in a straight line in a fixed direction, the frequency of the pump light is adjusted by the laser optical chopper, and the pump light is reflected by the mirror to adjust the forward direction of the pump light to the set The geometric relationship is focused on the excitation sample of the sample loading subsystem, the pump light energy of the sample to be tested is measured by an optical power meter, and the energy of the pump light is adjusted by an optical filter to obtain the required laser pulse energy. The probe light passes through the white light crystal, the beam shrinking and expanding subsystem, the beam homogenization and the spot homogenization device in sequence, and then outputs the detection white light with uniform light intensity distribution, and converts the incident laser light into an output beam with the required shape through the pulse shaping subsystem. After the probe light is output by the optical time-delay translation stage, the probe light with an adjustable time interval from the pump light is output, which is focused to the surface of the sample to be tested through an adjustable focusing lens for illumination, and the sample loading subsystem is controlled by the computer control subsystem to delay Move in three mutually perpendicular directions to move the area to be excited of the sample to coincide with the focal spot of the pump light and probe light, and use the hyperspectral camera to capture the kinetic signal of the femtosecond laser excitation on the surface of the sample to be tested Carry out shooting, signal amplification and recording, collect image information in the spectral band, use the computer control subsystem to read and process the image information output by the hyperspectral camera shooting subsystem, and obtain the two-dimensional spectral signal and two-dimensional imaging information of the sample to be tested.

The beneficial effects of the present invention are: the present invention uses the femtosecond pulse outputted by the femtosecond laser to split into pump light and probe light, the pump light is focused to the sample surface for excitation through the lens, and the probe light is detected after being reflected by the time-delay reflector. The optical signal is received by the hyperspectral camera, and the two-dimensional image information and two-dimensional spectral information are output by the computer. In the present invention, a hyperspectral camera is used to replace the traditional CCD camera to collect image information of hundreds of spectral bands of the instantaneous evolution state of the sample surface, and the non-linear effect makes the sample surface series of ultrafast instantaneous states show different images under multiple spectral imaging. Information, so that the imaging spectroscopy system with spatial resolution can extend the resolution of the target from pure spectrum to spectral recognition combined with the geometric characteristics of the target, so as to obtain more information about the ultrafast plasma in different time domains and frequency domains on the surface of the sample to be tested. information on bulk evolution and phase transitions.

Further, the femtosecond laser includes a femtosecond pulse oscillator, a chirped pulse amplification subsystem, and a laser control subsystem;

The femtosecond pulse is generated by the femtosecond pulse oscillator, amplified by the chirped pulse amplification subsystem to obtain a high-energy femtosecond pulse, and the pulse signal synchronized with the femtosecond pulse is output to the pulse signal generator and the computer by the laser control subsystem control subsystem.

The beneficial effect of the above-mentioned further solution is: the present invention utilizes the chirped pulse amplification subsystem to obtain high-energy femtosecond pulses, which carry high enough energy to excite the material surfaces under different ablation thresholds, and generate burnt pulses on the surfaces. The ablation effect is generated to generate corresponding ablation signals, and it is convenient to adjust the femtosecond pulse energy by using optical filters later.

Still further, the beam splitter is a non-polarizing beam splitter with a splitting ratio of 3:1.

The beneficial effect of the above further scheme is: after passing through the beam splitter, the pumping light obtains 3/4 of the energy, the light intensity is enough to excite the surface of the material, and the detection light obtains 1/4 of the energy, and has a high enough light intensity for illumination material surface.

Still further, the optical delay translation stage includes a computer control subsystem of the translation stage and the translation stage;

The position of the translation platform is adjusted through the computer control subsystem of the translation platform, and the time interval between the arrival of the probe light and the pump light at the sample to be tested is controlled.

The beneficial effect of the above further scheme is that the probe light will change from a single wavelength of light to white light with uniform light intensity distribution of multiple wavelengths, and an optical path from femtosecond to nanosecond can be generated between the pump light and the probe light. Poor, the probe light can reach the sample surface within different time intervals from femtoseconds to nanoseconds after the sample is excited by the pump light, and illuminate the surface of the sample to be tested, so that the hyperspectral camera can capture the femtosecond to nanosecond time interval after the pump light excites the sample. Optical signals at different time intervals of seconds.

Still further, the hyperspectral camera shooting subsystem includes a hyperspectral camera and a computer;

Use a hyperspectral camera to detect the optical information intensity signal generated after the surface of the sample to be tested is excited by the pump light, and use a computer to collect and output the optical information intensity signal to obtain multi-region two-dimensional spectral signals and two-dimensional imaging information with spatial resolution. .

The beneficial effect of the above further scheme is: due to the long exposure time of the hyperspectral camera, the computer controls the pulse signal generator to trigger and generate femtosecond pulses after triggering the hyperspectral camera to open the shutter laser for a certain period of time by setting the control algorithm, thereby realizing accurate single First exposure and image capture, record the instantaneous optical information of the material surface, and output multi-dimensional spectral images through computer data.

Still further, the hyperspectral camera is placed on the image plane of the hyperspectral camera shooting subsystem, a filter and a tube lens are also arranged in front of the hyperspectral camera, and the object plane of the hyperspectral camera shooting subsystem is set With sample stage.

The beneficial effect of the above-mentioned further scheme is: after the detection light is reflected by the time-delay mirror, it detects the changes caused by the pump light-induced excitation of the surface of the sample to be measured under different time-delay lengths, and its optical signal will be received by the hyperspectral camera and passed through The computer outputs high-resolution two-dimensional image information and two-dimensional spectral information.

Still further, the optical power meter, the sample loading subsystem and the optical delay translation stage are all connected with the computer control subsystem.

The beneficial effect of the above further solution is that all the electronic instruments and equipment in the experimental device are linked and controlled by a computer, so that the experimental operation becomes simple, convenient and accurate.

The invention provides a laser time-frequency transformation observation method based on hyperspectral imaging, comprising the following steps:

S1. Send an instruction to the pulse signal generator to excite the femtosecond laser, and use the femtosecond laser to output a high-energy 800nm femtosecond pulse, and use a beam splitter to divide it into pump light and probe light;

S2. After being reflected by the mirror, use the focusing lens to focus the pump light onto the sample to be tested placed on the sample loading subsystem, so as to excite the sample to be tested;

S3. Use a laser optical chopper to adjust the frequency of the required pump light, use an optical power meter to measure the energy of the pump light of the sample to be tested, and use an optical filter to adjust the energy of the pump light to obtain the required laser pulse energy;

S4. Pass the detection light through the white light crystal to output the detection white light pulse, make the spot size meet the requirements of the incident aperture of the focusing lens through the beam shrinkage and beam expansion subsystem, and use the beam homogenization and spot homogenization device to shape the detection white light pulse, and the output is stable And the light intensity distribution is uniform to detect white light, and use the optical delay translation stage to output the probe light with adjustable time interval with the pump light, and focus it to the surface of the sample to be tested through the focusing lens for illumination;

S5. Use the computer control subsystem to control the sample loading subsystem to move along three mutually perpendicular directions, and move the area to be excited of the sample to be tested to coincide with the focused spot of the pump light and the probe light;

S6. Using the hyperspectral camera to shoot the subsystem, optical imaging and spectral imaging will be performed on the surface of the sample to be tested illuminated by the probe light through the tube lens, and the transient optical property information and spectral information of the excited sample surface to be tested will be collected. The two-dimensional spectral signal and two-dimensional imaging information of the sample to be tested are obtained.

The beneficial effects of the present invention are: the present invention utilizes the femtosecond laser beam output by the laser to split into pump light and probe light, the pump light is focused on the sample surface through a lens for excitation, and the probe light is reflected by a time-delay mirror to detect different time lengths The changes generated by the excitation of the surface of the sample to be measured are induced by the pump light, and the optical signal is received by the hyperspectral camera, and the two-dimensional image information and two-dimensional spectral information are output by the computer. In the present invention, a hyperspectral camera is used to replace the traditional CCD camera to collect image information of hundreds of spectral bands of the instantaneous evolution state of the sample surface, and the non-linear effect makes the sample surface series of ultrafast instantaneous states show different images under multiple spectral imaging. Information, so that the imaging spectroscopy system with spatial resolution can extend the resolution of the target from pure spectrum to spectral recognition combined with the geometric characteristics of the target, so as to obtain more information about the ultrafast plasma in different time domains and frequency domains on the surface of the sample to be tested. information on bulk evolution and phase transitions.

Further, the acquisition of the transient optical property information of the excited sample surface is:

Before the sample to be tested is pumped and excited, select a clean, unprocessed area and illuminate it with probe light, use a hyperspectral camera to shoot and record the optical properties at that moment as a background image;

Record the optical information obtained after the pump excitation of the sample to be tested as the excitation image;

The background image and the excitation image are compared and cropped to obtain the transient optical properties of the surface of the excited sample to be tested at an ultrafast scale.

The beneficial effect of the above further scheme is: combining hyperspectral imaging technology with optical pumping detection technology, obtaining more physical and chemical information and morphological information on the ultrafast scale of the material surface, and extracting ultrafast Two-dimensional spectral signals and two-dimensional image information on the time scale, so as to understand and explore the ultrafast dynamic process of femtosecond laser processing more comprehensively. In the test method, the trigger program of the laser and the spectral camera is set by the pulse generator to realize multiple imaging and fast imaging of the system, which improves the data collection efficiency of the system.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention.

Fig. 2 is a schematic structural diagram of an ultrafast laser time-frequency transformation observation method based on hyperspectral imaging technology according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of an optical path of an ultrafast laser time-frequency transformation observation method based on hyperspectral imaging technology according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of the application process of the ultrafast laser time-frequency transformation observation method based on hyperspectral imaging in this embodiment.

Among them, 1-femtosecond laser, 2-first beam splitter, 3-white light crystal, 4-beam reduction and expansion subsystem, 5-beam homogenization and spot homogenization device, 6-first mirror, 7- Second reflector, 8-third reflector, 9-optical delay translation stage, 10-fourth reflector, 11-fifth reflector, 12-beam splitter, 13-first focusing lens, 14-standby Test sample, 15-second focusing lens, 16-sixth reflector, 17-optical chopper, 18-optical filter, 19-seventh reflector, 20-tube lens, 21-second filter, 22-hyperspectral camera, 23-computer control subsystem, 24-pulse signal generator.

detailed description

The specific embodiments of the present invention are described below so that those skilled in the art can understand the present invention, but it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes Within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are included in the protection list.

Example 1

The invention provides a laser time-frequency conversion observation system based on hyperspectral imaging, including an optical platform and a femtosecond laser arranged on the optical platform, a pulse signal generator, a reflector, a beam splitter, a laser optical chopper, White light crystal, beam reduction and expansion subsystem, beam homogenization and spot homogenization device, focusing lens, aperture, optical power meter, optical filter, optical delay translation stage, pulse shaping subsystem, sample loading subsystem, Hyperspectral camera shooting subsystem and computer control subsystem;

The computer control subsystem issues instructions to the pulse signal generator, excites the femtosecond laser to output high-energy femtosecond pulses, and uses a beam splitter to divide the high-energy femtosecond pulses into pump light and probe light. The pump light is used for The sample to be tested is excited, and the probe light is used to detect the change of the optical properties of the surface of the sample to be tested after being excited by the pump light. The aperture is used to collimate the laser path so that it propagates in a straight line along a fixed direction to prevent the light from being skewed. The laser optical chopper adjusts the frequency of the pump light, uses the mirror to reflect the pump light to adjust the forward direction of the pump light, and focuses on the excitation sample of the sample loading subsystem with the set geometric relationship , use an optical power meter to measure the pump light energy of the sample to be tested, and use an optical filter to adjust the pump light energy to obtain the required laser pulse energy, and then pass the probe light through the white light crystal, beam shrinkage and beam expansion subsystems, After the beam homogenization and spot homogenization device, the detection white light with uniform light intensity distribution is output, and the incident laser light is converted into an output beam with the required shape through the pulse shaping subsystem, which improves the detection quality and imaging quality, and uses the optical delay translation stage to output After probing the light, output the probing light with an adjustable time interval from the pumping light, focus it on the surface of the sample to be tested through an adjustable focusing lens for illumination, and use the computer control subsystem to control the sample loading subsystem to move along three mutually perpendicular directions , move the area to be excited of the sample to be tested to coincide with the focused spot of the pump light and probe light, and use the hyperspectral camera imaging subsystem to photograph, amplify and record the kinetic signal after the femtosecond laser excites the surface of the sample to be tested , collect the image information of the spectral band, use the computer control subsystem to read and process the image information output by the hyperspectral camera shooting subsystem, and obtain the two-dimensional spectral signal and two-dimensional imaging information of the sample to be tested. The femtosecond laser includes a femtosecond pulse oscillator, a chirped pulse amplification subsystem, and a laser control subsystem; the femtosecond pulse is generated by the femtosecond pulse oscillator, and a high-energy femtosecond pulse is obtained after being amplified by the chirped pulse amplification subsystem , the high-energy femtosecond pulse carries enough photon energy to ablate the sample surface with different thresholds to generate spectral signals, and it is convenient to use optical filters to adjust the femtosecond pulse energy in the future, and use the laser control subsystem to communicate with the femtosecond pulse The pulse signal synchronized with the second pulse is output to the pulse signal generator and the computer control subsystem. The beam splitter is a non-polarizing beam splitter with a splitting ratio of 3:1. The optical delay translation stage includes a computer control subsystem of the translation stage and a translation stage; the position of the translation stage is adjusted by the computer control subsystem of the translation stage, and the time interval between the detection light and the pump light reaching the sample to be tested is controlled. The hyperspectral camera shooting subsystem includes a hyperspectral camera and a computer; the hyperspectral camera is used to detect the optical information intensity signal generated after the surface of the sample to be tested is excited by the pump light, and the computer is used to collect and output the optical information intensity signal to obtain a Spatially resolved multi-region two-dimensional spectral signals and two-dimensional imaging information. The hyperspectral camera is placed on the image plane of the hyperspectral camera shooting subsystem, a filter and a tube lens are also arranged in front of the hyperspectral camera, and a sample loading object is arranged on the object plane of the hyperspectral camera shooting subsystem tower. The optical power meter, the sample loading subsystem and the optical delay translation stage are all connected with the computer control subsystem.

In this embodiment, the femtosecond laser outputs high-energy 800nm femtosecond pulses, which are split by a beam splitter into two beams of pulses, which are respectively used as pump light and probe light. The pumping light concentrates the light beam on the sample to be tested placed on the sample loading subsystem through the lens, so as to excite the sample to be tested. The optical power meter is used to measure the energy of the pump light pulse that excites the sample, and the optical filter is used to adjust the energy of the pump light to obtain the laser pulse energy required in the experiment. Use an optical power meter to measure the pump light energy of the sample to be tested; the transmitted light becomes white light with multiple wavelengths after passing through the white light crystal, and the laser spot size is changed to an appropriate range by the beam shrinkage and beam expansion subsystem to conform to the subsequent optical path The incident aperture of the middle focusing lens, the optical delay translation stage will make the pump light and probe light delay from femtosecond to nanosecond level, and focus on the surface of the sample to be measured through the adjustable lens, which plays a role The role of lighting. The hyperspectral camera shooting subsystem will perform optical imaging and spectral imaging on the material surface illuminated by the probe light through the tube lens, collect the transient optical property information and spectral information of the excited material surface, and output the data through the internal processing and calculation of the camera .

In this embodiment, both the reflector and the focusing lens can be adjusted manually, and the forward direction of the light beam can be adjusted in combination with the diaphragm, so as to accurately focus on the area to be excited on the surface of the material.

In this embodiment, the femtosecond laser includes a femtosecond pulse oscillator, a chirped pulse amplification subsystem, and a laser control subsystem. The femtosecond pulse oscillator generates femtosecond pulses, which are amplified by the chirped pulse amplification system to obtain high-energy femtosecond pulses. Pulse: The laser control subsystem outputs the pulse signal synchronized with the femtosecond pulse to the pulse signal generator and the computer control subsystem, and is controlled by the computer control subsystem at the same time.

In this embodiment, the optical power meter, laser optical chopper, sample loading system and optical delay translation stage are all electrically connected to the computer control subsystem. The computer control subsystem reads the real-time femtosecond pulse energy measured by the optical power meter; and controls the stage to move in three mutually perpendicular directions to move the excited area of the sample to be in contact with the pump and probe light The focused spot coincides; the optical delay translation stage moves in one direction to generate the time interval between the pump light and the probe light required for the experiment.

In this embodiment, the hyperspectral camera shooting subsystem is composed of a hyperspectral camera, a tube lens and a computer. Due to the long exposure time of the hyperspectral camera, the computer controls the pulse after the hyperspectral camera is triggered to open the shutter laser for a certain period of time by setting a control algorithm. The signal generator triggers the generation of femtosecond pulses to achieve precise single exposure and image capture, record the instantaneous optical information on the surface of the material, and output multi-dimensional spectral images through the computer.

In this embodiment, due to the long exposure time of the hyperspectral camera, the computer control subsystem needs to set a certain time delay between controlling the pulse signal generator to trigger the generation of femtosecond pulses and triggering the hyperspectral camera to take pictures. The camera takes pictures, and then triggers the pulse signal generator after reaching a certain exposure time to excite femtosecond pulses, so that the hyperspectral camera can capture the changes of transient optical properties.

As shown in Figure 2, the structure of a femtosecond pump-detection system combined with a hyperspectral camera according to an embodiment of the present invention is given, including: femtosecond pulse emission, sample excitation, sample detection, light convergence and signal acquisition. Among them, the femtosecond pulse emission is used to emit the femtosecond pulse laser, and the pump light and the probe light are generated respectively through the beam splitter; the sample excitation is used to converge the pump light to the excited area of the sample to be measured; The sample detection is used to convert the probe light into an optical signal that can be detected by the hyperspectral camera, and focus it to the light converging part; the light converging part is used to overlap the pump light and the probe light on the area to be excited on the sample surface, where, The pump light is used to excite the sample to be tested, and the probe light is used to detect the change of the surface optical properties of the sample to be tested after being excited by the pump light; The intensity of optical properties changes, and the ultrafast kinetic data collection of the surface of the sample to be tested is completed, and the transient optical image and spectral image of the surface of the sample to be tested are obtained, so as to obtain the data with the combination of image and spectrum with spectral spatial resolution.

In this embodiment, as shown in FIG. 3 , FIG. 3 shows an optical path of a femtosecond pump-detection system according to an embodiment of the present invention. The femtosecond laser 1 is jointly controlled by the computer control subsystem 23 and the pulse signal generator 24 to generate 800nm femtosecond laser pulses, which are transmitted through the first beam splitter 2 to form probe light, and reflected to form pump light. The transmitted light becomes white light with multiple wavelengths after passing through the white light crystal 3, and the laser spot size is changed to an appropriate range by the beam shrinkage and beam expander subsystem 4 to meet the incident aperture of the focusing lens in the subsequent optical path, and then the white light passes through the beam uniform Homogenization and light spot homogenization device 5 to obtain light with uniform spatial distribution of light intensity. The optical delay translation stage 9 is composed of a first reflector 6, a second reflector 7, a third reflector 8, a fourth reflector 10 and an electric displacement stage. The pumping light is reflected by the first reflector 6 and then reflected by the seventh reflector 19 and the sixth reflector 16. After being focused by the second focusing lens 15, it is incident on the surface of the sample 14 to be tested for excitation. The slice 18 can be used to adjust the energy of the pump light, and the laser optical chopper 17 is used to adjust the natural frequency of the pump light so as to obtain the pump light with the required pulse interval. The probe light will be time-delayed with the pump light after passing through the optical time-delay translation stage 9, and the probe light will continue to pass through the fifth reflector 11, and after passing through the beam splitter 12, it will be focused by the first focusing lens 13 onto the sample to be tested 14. on the excitation area. The computer control subsystem 23 controls the three-dimensional movement of the translation stage equipped with the sample 14 to be tested, and combines the two focusing lenses 13 and 15 placed on the four-dimensional mirror frame to adjust the focused spots of the pump light and probe light on the sample surface to coincide. . After the transient optical signal generated by the excitation of the pump light on the surface of the sample to be measured is illuminated by the probe light, it is vertically reflected and reflected by the second beam splitter 12, and passes through the tube lens 20 to make the imaging quality higher, and passes through the second filter 21 to filter out the interfering scattered pump light and plasma luminescence interference, and the final optical property signal is photographed and recorded by the hyperspectral camera 22 . The computer control subsystem 23 can simultaneously control the pulse signal generator 24, the optical delay translation stage 9, the hyperspectral camera 22 and the object stage 14, so that each device can work in harmony, wherein, especially the pulse signal generator 24 and hyperspectral The synergy between the cameras 22, the long exposure time of the hyperspectral camera 22 requires the computer control subsystem to first start the shooting of the hyperspectral camera 22, and then control the pulse signal generator 24 at an appropriate time to trigger the femtosecond laser 1 to output femtosecond At the same time as the pulse, the hyperspectral camera 22 can take pictures, and the optical time-lapse translation stage 8 can generate a series of optical time-delays by moving, and finally the hyperspectral camera collects and amplifies and outputs femtosecond to nanosecond-level materials required for the experiment Surface transient two-dimensional optical images and spectral images, so as to extract the ultrafast dynamics information of the material surface in different frequency domains and time domains.

In this embodiment, the femtosecond laser is a titanium sapphire femtosecond laser produced by Spectra Physics. The maximum power of the laser is 3.5W, the center wavelength is 800nm, and the pulse width is 35fs. Time delay reflectivity up to 16ns.

The specific detection steps are: (1) without placing the sample to be tested, the hyperspectral camera receives the optical signal from the surface of the detection light illumination material as a reference signal and background; (2) the computer controls the hyperspectral camera to start exposure, and the optical chopper is set. After that, the pulse signal generator controls the laser to generate a femtosecond laser pulse; (3) the pump light passes through the chopper and then outputs the light of the natural frequency, and the detection light passes through the white light crystal, the beam reduction and expansion subsystem and the The beam homogenization and spot homogenization device outputs white illumination light with uniform light intensity distribution; (4) The movement of the optical translation stage causes a certain delay between the pump light and the probe light, and the hyperspectral camera quickly excites the pump light and is detected by the probe. The optical information of the surface area of the material illuminated by the light is captured, and the optical translation stage continues to move to generate more delays, and the hyperspectral camera continues to capture relevant optical information; (5) compare the shooting information under each detection delay with the reference signal After cutting the background image, the corresponding optical information under each time delay and the spectral information under the illumination of different wavelengths of probe light are obtained; (6) By rotating the control filter and repeating the above steps, the pumping energy under different energies can be obtained. Information on ultrafast dynamics of photoexcited material surfaces.

In this embodiment, the translation stage used to place the sample is a three-dimensional piezoelectric translation stage, and its three-dimensional displacement accuracy can reach 1nm, which is sufficient to ensure the accuracy requirements of the experiment for the spatial movement of the sample. In the experiment, it is necessary to strictly ensure that the pump objective lens, The detection objective lens is well coupled with the sample, so that the hyperspectral camera can accurately image the excitation information of the material surface. After the data obtained by the experimental measurement is processed by the computer, a series of optical property change laws from femtosecond to nanosecond can be obtained, and the resolution ability of materials is extended from pure spectrum to spectral recognition combined with the geometric characteristics of the target. Multi-frequency transient evolution information under ultrafast dynamics in different time domains, for example, by studying plasma excitation and analyzing the spatiotemporal evolution of plasma free electron density, the absorption mechanism of laser energy can be revealed; by studying plasma and shock waves Propagation and plasma radiation process, analyzing the evolution law of different types/compositions of plasma and shock wave/stress wave, can explore the law of laser energy deposition, analyze the surface transformation process at the microscopic scale, and finally reveal the material phase transition process. On this basis, by further optimizing the laser processing conditions, such as using femtosecond laser space-time shaping, the interaction process between the laser and the material can be regulated, so as to realize the effective regulation of the final processing shape and properties of the material, and improve the processing quality and precision , efficiency and consistency.

In this embodiment, the present invention controls the pulse triggering of the femtosecond laser through the computer and the pulse signal generator, the optical delay translation stage controls the time delay interval between the pump light and the probe light, and the optical filter controls the pump light energy, by scanning the interval between the pump light and the probe light, and combining the data obtained by the hyperspectral camera shooting system for processing, the time-evolving spatial image information of the measured sample surface under different energy excitations and the multi-band two dimensional spectral information.

Example 2

As shown in Figure 1, the present invention provides a laser time-frequency transformation observation method based on hyperspectral imaging, and its implementation method is as follows:

S1. Send an instruction to the pulse signal generator to excite the femtosecond laser, and use the femtosecond laser to output a high-energy 800nm femtosecond pulse, and use a beam splitter to divide it into pump light and probe light;

S2. After being reflected by the mirror, use the focusing lens to focus the pump light onto the sample to be tested placed on the sample loading subsystem, so as to excite the sample to be tested;

S3. Use a laser optical chopper to adjust the frequency of the required pump light, use an optical power meter to measure the energy of the pump light of the sample to be tested, and use an optical filter to adjust the energy of the pump light to obtain the required laser pulse energy;

S4. Pass the detection light through the white light crystal to output the detection white light pulse, make the spot size meet the requirements of the incident aperture of the focusing lens through the beam shrinkage and beam expansion subsystem, and use the beam homogenization and spot homogenization device to shape the detection white light pulse, and the output is stable And the light intensity distribution is uniform to detect white light, and use the optical delay translation stage to output the probe light with adjustable time interval with the pump light, and focus it to the surface of the sample to be tested through the focusing lens for illumination;

S5. Use the computer control subsystem to control the sample loading subsystem to move along three mutually perpendicular directions, and move the area to be excited of the sample to be tested to coincide with the focused spot of the pump light and the probe light;

S6. Using the hyperspectral camera to shoot the subsystem, optical imaging and spectral imaging will be performed on the surface of the sample to be tested illuminated by the probe light through the tube lens, and the transient optical property information and spectral information of the excited sample surface to be tested will be collected. The two-dimensional spectral signal and two-dimensional imaging information of the sample to be tested are obtained.

In this embodiment, the acquisition of the transient optical property information of the excited sample surface is:

Before the sample to be tested is pumped and excited, select a clean, unprocessed area and illuminate it with probe light, use a hyperspectral camera to shoot and record the optical properties at that moment as a background image;

Record the optical information obtained after the pump excitation of the sample to be tested as the excitation image;

The background image and the excitation image are compared and cropped to obtain the transient optical properties of the surface of the excited sample to be tested at an ultrafast scale.

As shown in Figure 4, the use process of the ultrafast laser time-frequency transformation observation method based on hyperspectral imaging technology of the present invention will be described in detail below through specific embodiments:

1. Adjust and collimate the optical path of the entire device to ensure the accurate propagation of the laser beam in the entire optical system, and place the sample on the electric displacement stage;

2. Initialize each instrument, set the value of the pulse signal generator, the computer control subsystem sets the parameters of the spectrum camera, and resets the position of the electric translation platform and the time-delay translation platform to zero;

3. Set the parameters of the electric translation stage and the time-lapse translation stage through the computer control subsystem, determine the moving step size, initial position and final position of the two, and set the storage of the spectrum camera acquisition system;

4. By moving the time-delay translation stage, try to pump and excite on the sample, and use the spectral camera to collect two-dimensional image information to ensure that the pump light and the probe light reach the sample surface at the same time, and set this time as the delay zero point;

5. Delay The translation stage moves a step to generate a delay of the pump light and the probe light. Because the exposure time of the spectrum camera is long, the spectrum camera shooting system is started first, and it is triggered by the pulse signal generator when it reaches the camera shooting point for a period of time. The laser generates laser light, the pump light will excite the sample surface, the probe light illuminates the sample surface, and the spectral camera collects the two-dimensional image information and two-dimensional spectral information under this time-lapse;

6. The spectral camera amplifies, processes and calculates the collected relevant information, obtains a series of transient spectral data and corresponding two-dimensional image information in the time domain, and saves and outputs them;

7. Determine whether the delay translation stage has moved to the set final delay, if yes, end the signal acquisition; if not, move the electric translation stage and the delay translation stage by one step, and repeat 5 and 6 to continue the test.

In the present invention, the femtosecond laser beam output by the laser is split into pump light and probe light. The pump light is focused on the sample surface through a lens for excitation, and the probe light is reflected by a time-delay reflector and then detected by the pump light for different time lengths. The optical signal of the change produced by the surface of the sample to be measured is received by the hyperspectral camera, and the two-dimensional image information and two-dimensional spectral information are output through the computer. In the present invention, a hyperspectral camera is used to replace the traditional CCD camera to collect image information of hundreds of spectral bands of the instantaneous evolution state of the sample surface, and the non-linear effect makes the sample surface series of ultrafast instantaneous states show different images under multiple spectral imaging. Information, so that the imaging spectroscopy system with spatial resolution can extend the resolution of the target from pure spectrum to spectral recognition combined with the geometric characteristics of the target, so as to obtain more information about the ultrafast plasma in different time domains and frequency domains on the surface of the sample to be tested. information on bulk evolution and phase transitions.

The described embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations, without departing from the essence of the present invention, any obvious improvement, replacement or modification that can be made by those skilled in the art All belong to the protection scope of the present invention.

Claims (9)

1. A laser time-frequency conversion observation system based on hyperspectral imaging, characterized in that it includes an optical platform and a femtosecond laser, a pulse signal generator, a mirror, a beam splitter, and a laser optical chopper arranged on the optical platform Optical filter, white light crystal, beam shrinking and expanding subsystem, beam homogenization and spot homogenization device, focusing lens, aperture, optical power meter, optical filter, optical delay translation stage, pulse shaping subsystem, sample loader System, hyperspectral camera shooting subsystem and computer control subsystem; The computer control subsystem issues instructions to the pulse signal generator to excite the femtosecond laser to output high-energy femtosecond pulses. The high-energy femtosecond pulses are divided into pump light and probe light by the beam splitter, and the laser path is controlled by the aperture. The collimation process makes it propagate in a straight line in a fixed direction, the frequency of the pump light is adjusted by the laser optical chopper, and the pump light is reflected by the mirror to adjust the forward direction of the pump light to the set The geometric relationship is focused on the excitation sample of the sample loading subsystem, the pump light energy of the sample to be tested is measured by an optical power meter, and the energy of the pump light is adjusted by an optical filter to obtain the required laser pulse energy. The probe light passes through the white light crystal, the beam shrinking and expanding subsystem, the beam homogenization and the spot homogenization device in sequence, and then outputs the detection white light with uniform light intensity distribution, and converts the incident laser light into an output beam with the required shape through the pulse shaping subsystem. After the probe light is output by the optical time-delay translation stage, the probe light with an adjustable time interval from the pump light is output, which is focused to the surface of the sample to be tested through an adjustable focusing lens for illumination, and the sample loading subsystem is controlled by the computer control subsystem to delay Move in three mutually perpendicular directions to move the area to be excited of the sample to coincide with the focal spot of the pump light and probe light, and use the hyperspectral camera to capture the kinetic signal of the femtosecond laser excitation on the surface of the sample to be tested Carry out shooting, signal amplification and recording, collect image information in the spectral band, use the computer control subsystem to read and process the image information output by the hyperspectral camera shooting subsystem, and obtain the two-dimensional spectral signal and two-dimensional imaging information of the sample to be tested. 2. The laser time-frequency conversion observation system based on hyperspectral imaging according to claim 1, wherein the femtosecond laser comprises a femtosecond pulse oscillator, a chirped pulse amplification subsystem and a laser control subsystem; The femtosecond pulse is generated by the femtosecond pulse oscillator, amplified by the chirped pulse amplification subsystem to obtain a high-energy femtosecond pulse, and the pulse signal synchronized with the femtosecond pulse is output to the pulse signal generator and the computer by the laser control subsystem control subsystem. 3. The laser time-frequency transformation observation system based on hyperspectral imaging according to claim 2, wherein the beam splitter is a non-polarizing beam splitter with a splitting ratio of 3:1. 4. the laser time-frequency transformation observation system based on hyperspectral imaging according to claim 3, is characterized in that, described optical delay translation platform comprises the computer control subsystem of translation platform and translation platform; The position of the translation platform is adjusted through the computer control subsystem of the translation platform, and the time interval between the probe light and the pump light reaching the sample to be tested is controlled. 5. The laser time-frequency transformation observation system based on hyperspectral imaging according to claim 4, wherein the hyperspectral camera shooting subsystem comprises a hyperspectral camera and a computer; Use a hyperspectral camera to detect the optical information intensity signal generated after the surface of the sample to be tested is excited by the pump light, and use a computer to collect and output the optical information intensity signal to obtain multi-region two-dimensional spectral signals and two-dimensional imaging information with spatial resolution. . 6. The laser time-frequency transformation observation system based on hyperspectral imaging according to claim 5, wherein the hyperspectral camera is placed on the image plane of the hyperspectral camera shooting subsystem, and the front of the hyperspectral camera is also provided with There are filters and tube lenses, and a sample stage is arranged on the object plane of the hyperspectral camera shooting subsystem. 7. The laser time-frequency transformation observation system based on hyperspectral imaging according to claim 6, wherein the optical power meter, the sample loading subsystem and the optical delay translation stage are all connected to the computer control subsystem. 8. The observation method of the laser time-frequency transformation observation system based on hyperspectral imaging according to any one of claims 1-7, characterized in that, comprising the following steps: S1. Send an instruction to the pulse signal generator to excite the femtosecond laser, and use the femtosecond laser to output a high-energy 800nm femtosecond pulse, and use a beam splitter to divide it into pump light and probe light; S2. After being reflected by the mirror, use the focusing lens to focus the pump light onto the sample to be tested placed on the sample loading subsystem, so as to excite the sample to be tested; S3. Use a laser optical chopper to adjust the frequency of the required pump light, use an optical power meter to measure the energy of the pump light of the sample to be tested, and use an optical filter to adjust the energy of the pump light to obtain the required laser pulse energy; S4. Pass the detection light through the white light crystal to output the detection white light pulse, make the spot size meet the requirements of the incident aperture of the focusing lens through the beam shrinkage and beam expansion subsystem, and use the beam homogenization and spot homogenization device to shape the detection white light pulse, and the output is stable And the light intensity distribution is uniform to detect white light, and use the optical delay translation stage to output the probe light with adjustable time interval with the pump light, and focus it to the surface of the sample to be tested through the focusing lens for illumination; S5. Use the computer control subsystem to control the sample loading subsystem to move along three mutually perpendicular directions, and move the area to be excited of the sample to be tested to coincide with the focused spot of the pump light and the probe light; S6. Using the hyperspectral camera to shoot the subsystem, optical imaging and spectral imaging will be performed on the surface of the sample to be tested illuminated by the probe light through the tube lens, and the transient optical property information and spectral information of the excited sample surface to be tested will be collected. The two-dimensional spectral signal and two-dimensional imaging information of the sample to be tested are obtained. 9. The laser time-frequency transformation observation method based on hyperspectral imaging according to claim 8, wherein the acquisition of the transient optical property information on the surface of the excited sample to be measured is: Before the sample to be tested is pumped and excited, select a clean, unprocessed area and illuminate it with probe light, use a hyperspectral camera to shoot and record the optical properties at that moment as a background image; Record the optical information obtained after pumping and exciting the sample to be tested as the excitation image; The background image and the excitation image are compared and cropped to obtain the transient optical properties of the surface of the excited sample to be tested at an ultrafast scale.

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