Ultrafast Pump-Probe Transient Absorption Imaging System Based on Area Array CMOS Camera

Abstract

The present invention relates to the field of optical detection technologies, and provides an ultrafast pump-probe transient absorption imaging system based on an area array CMOS camera, which includes a femtosecond light source module, a delay line platform module, a detection white light generation module, an excitation light chopping module, a beam combining and homogenizing module, a sample chamber module, a detection module, and a system control module. The femtosecond laser outputs femtosecond pulsed laser, which is split by a beam splitter. A part of the light serves as excitation light and enters the parametric amplifier; another part of the light serves as the fundamental frequency light of the detection light and is output to the delay line platform module; the delay line platform module delays the detection light relative to the excitation light to irradiate the sample; the detection white light generation module converts the fundamental frequency light of the detection light output by the delay line platform module into detection white light; the excitation light chopping module optically chops the excitation light output by the parametric amplifier to form pump excitation light. The present invention can achieve single imaging and fast imaging of the system, and greatly improves the acquisition efficiency of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of optical detection, and in particular, to an ultrafast pump-probe transient absorption imaging system and method based on a area array CMOS camera. Background Art

[0002] The ultrafast pump-probe transient absorption spectrometer technology is widely used in scientific research such as clean energy, new materials, optoelectronic devices, etc. Its unique technology realizes the acquisition of spectral evolution information of materials on the femtosecond (10 -15 -15 s) scale, analyzes the kinetic processes and mechanisms. Combined with a micro-region system, it can also achieve a high spatial resolution of up to 500 nm. However, this conventional testing method still tests a single point of the test sample. With the development of technology, the transient absorption imaging technology has emerged, which can further detect the entire spatial interface of the material.

[0003] The existing transient absorption imaging technologies mainly have two directions: one is that the sample is placed statically, and a galvanometer & confocal technology is used to control the pulsed laser for spatial plane scanning; the second is to use a piezoelectric electric displacement stage to realize the step movement of the sample and the pulsed laser is static to realize spatial scanning. Both of these methods can achieve spatial transient absorption spectral imaging. However, for spatial scanning, it is necessary to test point by point. Each point is used as a pixel of the imaging data, and it takes a long time to acquire an imaging data, resulting in disadvantages such as slow data acquisition speed, low imaging resolution, and slow testing. Moreover, the spatial resolution is limited by the spot size after the optical pulse is focused, and the resolution cannot be further improved. Summary of the Invention

[0004] The present invention mainly solves the technical problems such as slow data acquisition speed and low imaging resolution of the existing transient absorption spectral imaging technology, and proposes an ultrafast pump-probe transient absorption imaging system and method based on a area array CMOS camera to achieve one-time imaging and fast imaging of the system, greatly improving the acquisition efficiency of the system.

[0005] The present invention provides an ultrafast pump-probe transient absorption imaging system based on a area array CMOS camera, including: a femtosecond light source module, a delay line platform module, a detection white light generation module, an excitation light chopping module, a beam combining and homogenizing module, a sample chamber module, a detection module, and a system control module;

[0006] The femtosecond light source module includes: a femtosecond laser, a beam splitter, and a parametric amplifier;

[0007] The femtosecond laser outputs femtosecond pulsed laser, which is split by the beam splitter. One part of the light enters the parametric amplifier as the excitation light; the other part of the light is output as the fundamental frequency light of the detection light to the delay line platform module;

[0008] The delay line platform module controls the optical path of the fundamental frequency light of the probe light, so that the probe light irradiates the sample with a delay relative to the excitation light;

[0009] The probe white light generation module converts the fundamental frequency light of the probe light output by the delay line platform module into probe white light;

[0010] The excitation light chopping module optically chops the excitation light output by the parametric amplifier to form pump excitation light;

[0011] The beam combining and homogenizing module includes: a beam combining and splitting film and a spot homogenizing device;

[0012] The beam combining and splitting film transmits 50% of the probe white light and reflects 50% of the pump excitation light, making the probe white light and the pump excitation light in a coaxial and collinear state to synthesize combined light;

[0013] The spot homogenizing device performs spot homogenizing processing on the combined light;

[0014] The sample chamber module includes: a first objective lens, a second objective lens and a lens arranged in sequence; the first objective lens and the second objective lens have the same focal length; a sample is placed between the first objective lens and the focus of the first objective lens; a switchable filter is arranged behind the second objective lens;

[0015] The combined light performs surface excitation on the sample through the first objective lens. After the light passes through the sample, the second objective lens with the same focal length is used to collect the light, making the probe white light and the pump excitation light become parallel light again; the lens performs focusing;

[0016] The detection module includes: a probe light detector; the probe light detector collects the light focused by the lens; the probe light detector uses a area array CMOS camera;

[0017] The system control module includes: an industrial personal computer and a counter;

[0018] The counter is respectively connected to the femtosecond laser, the excitation light chopping module and the probe light detector in signal;

[0019] The industrial personal computer is respectively connected to the counter, the delay line platform module, the excitation light chopping module and the probe light detector in signal.

[0020] Preferably, the femtosecond laser outputs continuous femtosecond pulsed laser with a wavelength range of 200 nm - 2000 nm as the excitation light, and outputs pulsed light with a wavelength of 800 nm or 1030 nm as the fundamental frequency light of the probe light.

[0021] Preferably, the delay line platform module includes: a delay line platform and an external platform mirror;

[0022] The delay line platform and the off-platform mirror are respectively installed on the first displacement stage.

[0023] Preferably, the moving range of the delay line platform module is 0 to 300 mm, and the delay time of the delay line platform module for the probe light is 0 to 8 ns.

[0024] Preferably, the probe white light generation module includes: a first plano-convex lens, a first attenuation sheet, a white light generation crystal, a second plano-convex lens, a second attenuation sheet, and a first filter arranged in sequence.

[0025] Preferably, the excitation light chopping module includes: a second retroreflector, a first aperture positioning device, a chopper, a third attenuation sheet, and a second aperture positioning device; wherein, the chopper is signal-connected to the system control module.

[0026] Preferably, the sample chamber module is configured with a second displacement stage;

[0027] The first objective lens, the second objective lens, and the sample are placed on the second displacement stage, and the positions of the first objective lens, the second objective lens, and the sample are adjusted by the second displacement stage.

[0028] Preferably, the counter uses a counter of model NI-PCIe6612;

[0029] The counter generates a chopper trigger signal B with a frequency of A / 2 according to the synchronization signal A input by the femtosecond laser, and outputs it to the chopper;

[0030] The counter then generates a probe light detector trigger signal C with a frequency of 2B according to the chopper trigger signal B, and outputs it to the probe light detector;

[0031] Through the synchronization of these three signals, the synchronous output of the femtosecond laser, the chopper, and the probe light detector is realized.

[0032] Correspondingly, the present invention also provides an imaging method for an ultrafast pump-probe transient absorption imaging system based on a matrix CMOS camera according to any embodiment of the present invention, which is characterized by including the following processes:

[0033] Step 100, perform system configuration: turn on the device power supply, set the output of the femtosecond laser, set the parametric amplifier to output light of a corresponding wavelength as the excitation light of the test system, place the sample on the sample placement position of the sample chamber module, and set the scanning parameters of the imaging system;

[0034] Step 200: The industrial control computer initializes the counter, delay line platform module, excitation light chopping module, and detection light detector. The industrial control computer controls the counter to receive the synchronization signal A from the femtosecond laser. The frequency of the synchronization signal A is f, and based on this synchronization signal A, a chopper trigger signal B with a frequency of f / 2 is generated and output to the chopper to achieve excitation light pumping excitation.

[0035] Step 300: The industrial control computer system performs ultrafast pump-probe transient absorption imaging on the sample.

[0036] Step 400: The industrial control computer controls the start of scanning. The industrial control computer delay line platform module moves according to the scanning parameters set in Step 300. After each point is moved and stabilized, the industrial control computer controls the counter to generate a detection light detector trigger signal C with a frequency of f based on signal B and outputs it to the detection light detector to control the detection light detector to perform scanning, obtaining the data of the excited state transmitted light intensity and the unexcited state transmitted light intensity at each delay time, and further obtaining the transient absorption signal.

[0037] Step 500: Record the transient absorption information, delay information, and imaging pixel information as the final system data and save it.

[0038] Preferably, Step 300 includes the following processes:

[0039] Step 301: The femtosecond laser outputs femtosecond pulsed laser, which is split by a beam splitter. One part of the light enters the parametric amplifier as the excitation light, and the other part of the light, which is the fundamental frequency light of the probe pulsed light, is output to the delay line platform module.

[0040] Step 302: The delay line platform module controls the optical path of the fundamental frequency light of the probe pulsed light so that the probe light irradiates the sample with a delay relative to the excitation light.

[0041] Step 303: Convert the fundamental frequency light of the probe pulsed light output by the delay line platform module into probe white light.

[0042] Step 304: Optically chop the excitation light output by the parametric amplifier to form pump excitation light.

[0043] Step 305: The beam combining beam splitter transmits 50% of the probe white light and reflects 50% of the pump excitation light, making the probe white light and the pump excitation light in a coaxial and collinear state to form combined light. The spot homogenization device performs spot homogenization processing on the combined light.

[0044] Step 306: The first objective lens realizes surface excitation and surface detection of the combined light on the sample. After the light passes through the sample, the second objective lens with the same focal length collects the light, making the probe white light and the pump excitation light become parallel light again. The lens focuses the light.

[0045] Step 307: The probe light detector collects the light focused by the collecting lens.

[0046] An ultrafast pump-probe transient absorption imaging system and method based on a planar array CMOS camera provided by the present invention homogenize the light spot through the light beam combining and homogenizing module V, making the light intensity uniform within a certain area. Through the sample chamber module, surface excitation and detection of the sample by light are realized. Through the high-speed surface acquisition of the planar array CMOS camera in the detection module, fast imaging of the system is achieved, and one-time imaging is realized, greatly improving the acquisition efficiency of the system. The present invention overcomes the technical problem in the prior art that imaging data is scanned pixel by pixel, with imaging being performed point by point and the imaging efficiency being low. Description of the Drawings

[0047] Figure 1 is the schematic composition diagram of the ultrafast pump-probe transient absorption imaging system based on a planar array CMOS camera provided by the present invention;

[0048] Figure 2 is the schematic optical path diagram of the delay line platform provided by the present invention;

[0049] Figure 3 is the schematic diagram of pump delay detection of the excitation light chopping module provided by the present invention;

[0050] Figure 4 is the schematic diagram of the light beam homogenization effect of the light beam combining and homogenizing module provided by the present invention;

[0051] Figure 5 is the schematic optical path diagram of the sample chamber module provided by the present invention;

[0052] Figure 6a -c is the schematic diagram of the scanning curves of three scanning modes provided by the present invention.

[0053] Reference numerals: Ⅰ. Femtosecond light source module; Ⅱ. Delay line platform module; Ⅲ. Probe white light generation module; Ⅳ. Excitation light chopping module; Ⅴ. Beam combining and homogenizing module; Ⅵ. Sample chamber module; Ⅶ. Detection module; Ⅷ. System control module; 1. Femtosecond laser; 2. Beam splitter; 3. Parametric amplifier; 4. Delay line platform; 5. External platform mirror; 6. First plano-convex lens; 7. First attenuation sheet; 8. White light crystal; 9. Second plano-convex lens; 10. Second attenuation sheet; 11. First filter; 12. Second retroreflector; 13. First aperture positioning device; 14. Chopper; 15. Third attenuation sheet; 16. Second aperture positioning device; 17. Beam combining and splitting sheet; 18. Spot homogenizing device; 19. First objective lens; 20. Sample; 21. Second objective lens; 22. Lens; 23. Probe light detector; 24. Counter; 25. Industrial control computer; 401. First internal platform mirror; 402. Second internal platform mirror; 403. Third internal platform mirror; 404. Fourth internal platform mirror; 405. Fifth internal platform mirror; 406. Sixth internal platform mirror; 407. Seventh internal platform mirror. Detailed implementation manners

[0054] To make the technical problems solved by the present invention, the technical solutions adopted and the achieved technical effects clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only the parts related to the present invention are shown in the drawings rather than all the content.

[0055] As Figure 1 shown, the ultrafast pump-probe transient absorption imaging system based on a matrix CMOS camera provided by an embodiment of the present invention includes: a femtosecond light source module Ⅰ, a delay line platform module Ⅱ, a probe white light generation module Ⅲ, an excitation light chopping module Ⅳ, a beam combining and homogenizing module Ⅴ, a sample chamber module Ⅵ, a detection module Ⅶ, and a system control module Ⅷ.

[0056] The femtosecond light source module Ⅰ includes: a femtosecond laser 1, a beam splitter 2, and a parametric amplifier 3. The femtosecond laser 1 outputs femtosecond pulsed laser, which is split by the beam splitter 2. One part of the light enters the parametric amplifier 3 as excitation light; the other part of the light is output as the fundamental frequency light of the probe light to the delay line platform module Ⅱ.

[0057] In the femtosecond light source module Ⅰ, the femtosecond laser 1 outputs continuous femtosecond pulsed laser of 200 nm - 2000 nm as excitation light, and outputs pulsed light of 800 nm or 1030 nm as the fundamental frequency light of the probe light.

[0058] The main function of the femtosecond light source module Ⅰ is to provide the excitation light source (200nm - 2000nm) for the system and the fundamental frequency light of the detection pulsed light of the system (800nm or 1030nm pulsed light, output by the femtosecond laser). The pulse width of the pulsed light of the laser light source determines the time resolution of the system. Generally, the instrument response function (IRF) of the system is 1.5 times the pulse width. There are two types of femtosecond lasers 1 that can be selected. One can choose the LIGHT CONVERSION (LC) 1030nm 100K laser, and the other can choose the 800nm 1K laser of Coherent or Spectra-Physics.

[0059] The delay line platform module Ⅱ controls the optical path of the fundamental frequency light of the detection light, so that the detection light irradiates the sample with a delay relative to the excitation light.

[0060] The delay line platform module Ⅱ includes: a delay line platform 4 and an external platform mirror 5. The delay line platform 4 and the external platform mirror 5 are respectively installed on the first displacement stage. As Figure 2 shown, a plurality of internal platform mirrors are arranged in the delay line platform 4. Specifically, the delay line platform 4 includes: a first internal platform mirror 401, a second internal platform mirror 402, a third internal platform mirror 403, a fourth internal platform mirror 404, a fifth internal platform mirror 405, a sixth internal platform mirror 406, and a seventh internal platform mirror 407;

[0061] The seventh internal platform mirror 407 is arranged at one end of the delay line platform 4, and the other internal platform mirrors are arranged at the other end of the delay line platform 4;

[0062] The fifth internal platform mirror 405 and the sixth internal platform mirror 406 are arranged correspondingly; the third internal platform mirror 403 and the fourth internal platform mirror 404 are arranged behind the fifth internal platform mirror 405; the first internal platform mirror 401 and the second internal platform mirror 402 are arranged behind the sixth internal platform mirror 406; the third internal platform mirror 403 corresponds to the position of the second internal platform mirror 402;

[0063] Moreover, the first internal platform mirror 401, the second internal platform mirror 402, the third internal platform mirror 403, the fourth internal platform mirror 404, the fifth internal platform mirror 405, and the sixth internal platform mirror 406 are respectively at an angle of 45° with the length direction of the delay line platform 4.

[0064] The first platform internal mirror 401, the second platform internal mirror 402, the third platform internal mirror 403, and the fourth platform internal mirror 404 are mirrors with a circular diameter of 25.1 mm. The fifth platform internal mirror 405 and the sixth platform internal mirror 406 are square mirrors. The seventh platform internal mirror 407 is a hollow conical mirror, placed on the first displacement stage. ①, ②, ③, ④, ⑤, ⑥, ⑦, ⑧ are the optical path sequences.

[0065] After the fundamental frequency light output by the femtosecond light source module I enters the delay line platform 4, it is reflected by multiple platform internal mirrors within the delay line platform 4. The function of the delay line platform module II is to set the optical path of the fundamental frequency light of the probe light in the system. The moving range of the delay line platform module II is 0 to 300 mm, and the fundamental frequency light can be reflected 8 times within the delay line platform 4. According to the speed of light C = 3×10 8 m / s, the delay time of the delay line platform module II for the probe light is 0 to 8 ns (10 -9 s).

[0066] The detection white light generation module III converts the fundamental frequency light of the probe light output by the delay line platform module II into detection white light. The detection white light generation module III includes: a first plano-convex lens 6, a first attenuation sheet 7, a white light generation crystal 8, a second plano-convex lens 9, a second attenuation sheet 10, and a first filter 11 arranged in sequence.

[0067] Function of the detection white light generation module III: It is to convert the fundamental frequency light output by the delay line platform module II into detection white light. The white light generation crystal 8 in the detection white light generation module III can be set according to actual experimental needs. By selecting different crystals, the relationship between the detection wavelength range of the white light spectrum is as follows:

[0068] 800 nm light source: Calcium fluoride crystal 3 mm: 350 nm - 700 nm; Sapphire crystal 3 mm: 439 nm - 800 nm;

[0069] 1030 nm light source: Sapphire crystal 3 mm: 400 nm - 700 nm; Yag crystal 13 mm: 530 nm - 950 nm.

[0070] The excitation light chopping module IV optically chops the excitation light output by the parametric amplifier 3 to form pump excitation light. The excitation light chopping module IV includes: a second retroreflector 12, a first aperture positioning device 13, a chopper 14, a third attenuation sheet 15, and a second aperture positioning device 16 arranged in sequence; among them, the chopper 14 is signal-connected to the system control module VIII.

[0071] The function of the excitation light chopping module Ⅳ is to optically chop the excitation light output by the parametric amplifier 3 to form pump excitation light. Taking the 800nm 1K laser light source as an example, with the same frequency of 1K, the chopper 14 is set to 0.5kHz. As Figure 3 shown, the chopper 14 can block the intermittent pulsed light, forming pump-probe relative to the probe light. The combined action of the excitation light chopping module Ⅳ and the delay line platform module Ⅱ realizes optical pumping and delayed detection.

[0072] The beam combining and homogenizing module Ⅴ includes: a beam combining and splitting film 17 and a spot homogenizing device 18; after the pump excitation light output by the excitation light chopping module Ⅳ and the probe white light output by the probe white light generation module Ⅲ enter the beam combining and homogenizing module Ⅴ, the beam combining and splitting film 17 transmits 50% of the probe white light and reflects 50% of the pump excitation light, putting the probe white light and the pump excitation light in a coaxial and collinear state to synthesize a combined beam; the spot homogenizing device 18 performs spot homogenizing processing on the combined beam.

[0073] Before the spot homogenizing processing, the spatial intensity distribution states of the two beams of light are Gaussian beams. Before the beams are homogenized, as Figure 4 shown in the left figure, the photon density distributions are strong in the middle and weak around. When such a beam is focused on the sample, it is impossible to achieve an uneven excitation area. Therefore, when the beam passes through the spot homogenizing device, the spot will become relatively uniform, as Figure 4 shown on the right. The spot homogenizing device 18 can use Edmund Optics' beam shaper (πShaper6_6_VIS).

[0074] The sample chamber module Ⅵ includes: a first objective lens 19, a second objective lens 21, and a lens 22 arranged in sequence; the first objective lens 19 and the second objective lens 21 have the same focal length; a sample 20 is placed between the first objective lens 19 and the focus of the first objective lens 19; a switchable filter is arranged behind the second objective lens 21;

[0075] The combined beam is used by the first objective lens 19 to perform surface excitation on the sample 20. After the light passes through the sample 20, the second objective lens 21 with the same focal length is used to collect the light, making the probe white light and the pump excitation light become parallel light again; the lens 22 performs focusing;

[0076] The sample chamber module Ⅵ is configured with a second displacement stage; the first objective lens 19, the second objective lens 21, and the sample 20 are placed on the second displacement stage, and the positions of the first objective lens 19, the second objective lens 21, and the sample 20 are adjusted through the second displacement stage.

[0077] The sample chamber module VI uses a 50X objective lens for light focusing to achieve micro-drive detection. A second displacement stage in the XYZ directions is set to ensure that the focal points of the first objective lens 19 and the second objective lens 21 coincide, and the Z axes coincide. In the existing sample setting, the sample is generally set at the focal point to achieve micro-region point detection. In the present invention, the sample 20 is set between the focal point and the incident light objective lens to form an excitation light surface excitation and a detection light surface detection. Specifically, as Figure 5 shown, a switchable filter is placed behind the second objective lens 21 to filter out the excitation light and intercept the detectable wavelength of the response. Through experiments, the distance between the sample 20 and the first objective lens 19 is half of the focal length of the first objective lens 19, and the formula is as follows:

[0078] D = f / 2

[0079] where D represents the distance between the sample 20 and the first objective lens 19, and f is the focal length of the first objective lens 19.

[0080] The detection module VII includes: a detection light detector 23; the detection light detector 23 collects the light focused by the collection lens 22; the detection light detector 23 uses a area array CMOS camera. When selecting the area array CMOS camera, parameters such as pixel resolution, pixel size, and acquisition frequency need to be mainly considered. Pixel resolution and pixel size: affect the pixel resolution of the final data imaging; acquisition frequency: affect the acquisition efficiency.

[0081] In the present invention, an example detector for the detection light detector 23 has a pixel output of 480*320 and a pixel depth of 10 bit, and can perform data acquisition at a frequency of 1Khz. Theoretically, when selecting an area array CMOS camera with higher parameters, the resolution and acquisition efficiency of the system will be higher.

[0082] The system control module VIII includes: an industrial control computer 25 and a counter 24; the counter 24 is respectively connected to the femtosecond laser 1, the excitation light chopper module IV, and the detection light detector 23 in a signal connection. The industrial control computer 25 is respectively connected to the counter 24, the delay line platform module II, the excitation light chopper module IV, and the detection light detector 23 in a signal connection. The industrial control computer 25 is responsible for driving and controlling the logical operation and data acquisition of devices such as the counter 24, the delay line platform 4, the chopper 14, and the detection light detector 23.

[0083] The counter 24, as the core component of the system, mainly functions to control the operation of each device system. The counter 24 uses a counter of the NI-PCIe6612 model; according to the synchronization signal A input by the femtosecond laser 1, the counter 24 generates a chopper trigger signal B with a frequency of A / 2 and outputs it to the chopper 14; then, according to the chopper trigger signal B, the counter 24 generates a probe light detector trigger signal C with a frequency of 2B and outputs it to the probe light detector 23; through the synchronization of these three signals, the synchronous output of the femtosecond laser 1, the chopper 14, and the probe light detector 23 is realized.

[0084] The ultrafast pump-probe transient absorption imaging system based on a matrix CMOS camera provided by the present invention homogenizes the light spot through the beam combining and homogenizing module V, making the light intensity uniform within a certain area. Through the sample chamber module VI, surface excitation and detection of the sample by light are realized. Through the high-speed surface acquisition of the matrix CMOS camera in the detection module VII, fast imaging of the system is realized, achieving one-time imaging and overcoming the technical problems of the prior art that imaging data is scanned pixel by pixel, with low imaging efficiency for scanning point by point imaging. The present invention greatly improves the acquisition efficiency of the system. The acquisition speed is increased by more than 20 times. To acquire a set of imaging data with 200 delay points and a pixel of 480*320, it only takes about 10 minutes. For surface array excitation, the scanning resolution is no longer limited by the laser spot diffraction limit (500nm), and the resolution can be increased by more than 10 times, reaching more than 50nm.

[0085] The present invention also provides an imaging method for an ultrafast pump-probe transient absorption imaging system based on a matrix CMOS camera, including the following processes:

[0086] Step 100, perform system configuration.

[0087] Turn on the device power supply, set the output of the femtosecond laser 1, and set the parametric amplifier 3 to output light with a corresponding wavelength as the excitation light of the test system according to the test requirements. Place the sample on the sample placement position of the sample chamber module VI. Set the scanning parameters of the imaging system, including selecting the scanning mode and determining the scanning range step size; among them, the scanning mode includes linear scanning ( Figure 6a ), exponential scanning ( Figure 6b ), and segmented linear scanning (6c); the scanning range step size includes start, end, and step size.

[0088] Step 200, the industrial control computer 25 initializes the counter 24, the delay line platform module II, the excitation light chopping module (IV), and the probe light detector 23; the industrial control computer 25 controls the counter 24 to receive the synchronization signal A of the femtosecond laser 1, the frequency of the synchronization signal A is f, and according to this synchronization signal A, a chopper trigger signal B with a frequency of f / 2 is generated and output to the chopper 14 to realize pump excitation of the excitation light.

[0089] Step 300, the industrial control computer 25 control system performs ultrafast pump-probe transient absorption imaging on the sample.

[0090] Step 400, the industrial control computer 25 controls the start of the scan. The industrial control computer 25 delay line platform module II moves according to the scan parameters set in step 300. After stabilizing at each moved point, the industrial control computer 25 controls the counter 24 to generate a probe light detector trigger signal C with a frequency of f according to signal B, and outputs it to the probe light detector 23 to control the probe light detector 23 to perform a scan, obtaining the excited state transmitted light intensity I 1-pump and the non-excited state transmitted light intensity I 1-unpump data, and then obtaining the transient absorption signal.

[0091] Among them, the number of scans at each point is equal to the scan parameters of step 100;

[0092] The number of data collected by the probe light detector 23 is N, where the number of odd data N / 2 is I 1-pump , and the number of even data N / 2 is I 1-unpump ;

[0093] Transient absorption signal: ΔA = -Log(I 1-pump / I 1-unpump )

[0094] Among them, ΔA is the change in the absorption of the corresponding wavelength light by the test sample after changing from the ground state to the excited state. The formula ΔA = A pump -A unpump = -Log(I 1-pump / I 1-unpump ), where A pump is the excited state absorption light intensity, A unpump is the non-excited state absorption light intensity, I 1-pump is the excited state transmitted light intensity, I 1-unpump is the non-excited state transmitted light intensity.

[0095] Step 500, record the three data information of the transient absorption information ΔA, the delay information Delay, and the imaging pixel information CMOS PIX as the final system data and save it.

[0096] Among them, at each Delay, there will be a transient absorption signal ΔA under each CMOS PIX.

[0097] The said step 300 includes the following process:

[0098] Step 301, the femtosecond laser 1 outputs femtosecond pulsed laser, which is split by the beam splitter 2. A part of the light enters the parametric amplifier 3 as the excitation light; the other part of the light, which is the fundamental frequency light of the probe pulsed light, is output to the delay line platform module II.

[0099] Step 302, the delay line platform module II controls the optical path of the fundamental frequency light of the probe pulsed light, so that the probe light irradiates the sample with a delay relative to the excitation light.

[0100] Step 303, convert the fundamental frequency light of the probe pulsed light output by the delay line platform module II into probe white light.

[0101] Step 304, optically chop the excitation light output by the parametric amplifier 3 to form pump excitation light.

[0102] Step 305, the beam combining and splitting sheet 17 transmits 50% of the probe white light and reflects 50% of the pump excitation light, making the probe white light and the pump excitation light in a coaxial and collinear state to form combined light; the spot homogenizing device 18 performs spot homogenization processing on the combined light.

[0103] Step 306, the first objective lens 19 realizes surface excitation and surface detection of the combined light on the sample 20. After the light passes through the sample 20, the second objective lens 21 with the same focal length collects the light, making the probe white light and the pump excitation light become parallel light again; the lens 22 focuses the light.

[0104] Step 307, the probe light detector 23 collects the light focused by the lens 22.

[0105] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: modifying the technical solutions recorded in the foregoing embodiments, or equivalently replacing some or all of the technical features therein, does not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ultrafast pump-probe transient absorption imaging system based on an area array CMOS camera, characterized in that, Including: A femtosecond light source module (Ⅰ), a delay line platform module (Ⅱ), a detection white light generation module (Ⅲ), an excitation light chopping module (Ⅳ), a beam combining and homogenizing module (Ⅴ), a sample chamber module (Ⅵ), a detection module (Ⅶ), and a system control module (Ⅷ); The femtosecond light source module (Ⅰ) includes: a femtosecond laser (1), a beam splitter (2), and a parametric amplifier (3); The femtosecond laser (1) outputs femtosecond pulsed laser, which is split by the beam splitter (2). A part of the light enters the parametric amplifier (3) as excitation light; another part of the light is output as the fundamental frequency light of the detection light to the delay line platform module (Ⅱ); The delay line platform module (Ⅱ) controls the optical path of the fundamental frequency light of the detection light to make the detection light irradiate the sample with a delay relative to the excitation light; The detection white light generation module (Ⅲ) converts the fundamental frequency light of the detection light output by the delay line platform module (Ⅱ) into detection white light; The detection white light generation module (Ⅲ) includes: a first plano-convex lens (6), a first attenuation sheet (7), a white light generation crystal (8), a second plano-convex lens (9), a second attenuation sheet (10), and a first filter (11) arranged in sequence; The excitation light chopping module (Ⅳ) optically chops the excitation light output by the parametric amplifier (3) to form pump excitation light; The excitation light chopping module (Ⅳ) includes: a retroreflector (12), a first aperture positioning device (13), a chopper (14), a third attenuation sheet (15), and a second aperture positioning device (16) arranged in sequence; wherein, the chopper (14) is signal-connected to the system control module (Ⅷ); The beam combining and homogenizing module (Ⅴ) includes: a beam combining and splitting sheet (17) and a spot homogenizing device (18); The beam combining and splitting sheet (17) transmits 50% of the detection white light and reflects 50% of the pump excitation light, making the detection white light and the pump excitation light in a coaxial and collinear state to synthesize combined light; The spot homogenizing device (18) performs spot homogenizing processing on the combined light; The sample chamber module (Ⅵ) includes: a first objective lens (19), a second objective lens (21), and a lens (22) arranged in sequence; the first objective lens (19) and the second objective lens (21) have the same focal length; a sample (20) is placed between the focal points of the first objective lens (19) and the second objective lens (21); a switchable filter is arranged behind the second objective lens (21); The combined light performs surface excitation on the sample (20) through the first objective lens (19). After the light passes through the sample (20), the light is collected by the second objective lens (21) with the same focal length to make the detection white light and the pump excitation light become parallel light again; the lens (22) performs focusing; The detection module (Ⅶ) includes: a detection light detector (23); the detection light detector (23) collects the light focused by the lens (22); the detection light detector (23) uses a planar array CMOS camera; The system control module (Ⅷ) includes: an industrial control computer (25) and a counter (24); The counter (24) is respectively connected to the femtosecond laser (1), the excitation light chopping module (IV), and the detection light detector (23) in terms of signal connection; The industrial control computer (25) is respectively connected to the counter (24), the delay line platform module (II), the excitation light chopping module (IV), and the detection light detector (23) in terms of signal connection.

2. The ultrafast pump-probe transient absorption imaging system based on a matrix CMOS camera according to claim 1, wherein The femtosecond laser (1) outputs continuous femtosecond pulsed laser with a wavelength range of 200nm - 2000nm as the excitation light, and outputs pulsed light with a wavelength of 800nm or 1030nm as the fundamental frequency light of the detection light.

3. The ultrafast pump-probe transient absorption imaging system based on a matrix CMOS camera according to claim 1, characterized in that, The delay line platform module (II) includes: a delay line platform (4) and an external platform mirror (5); The delay line platform (4) and the external platform mirror (5) are respectively installed on the first displacement stage.

4. The ultrafast pump-probe transient absorption imaging system based on a matrix CMOS camera according to claim 3, wherein The moving range of the delay line platform module (II) is from 0 to 300mm, and the delay time of the delay line platform module (II) for the detection light is from 0 to 8ns.

5. The ultrafast pump-probe transient absorption imaging system based on an area array CMOS camera according to claim 1, wherein The sample chamber module (VI) is configured with a second displacement stage; The first objective lens (19), the second objective lens (21), and the sample (20) are placed on the second displacement stage, and the positions of the first objective lens (19), the second objective lens (21), and the sample (20) are adjusted through the second displacement stage.

6. The ultrafast pump-probe transient absorption imaging system based on a matrix CMOS camera according to claim 1, characterized in that, The counter (24) adopts a counter of model NI - PCIe6612; The counter (24) generates a chopper trigger signal B with a frequency of A / 2 according to the synchronization signal A input by the femtosecond laser (1), and outputs it to the chopper (14); The counter (24) then generates a detection light detector trigger signal C with a frequency of 2B according to the chopper trigger signal B, and outputs it to the detection light detector (23); Through the synchronization of these three signals, the synchronous output of the femtosecond laser (1), the chopper (14), and the detection light detector (23) is achieved.

7. An imaging method for an ultrafast pump-probe transient absorption imaging system based on an area array CMOS camera according to any one of claims 1 to 6, characterized in that, It includes the following processes: Step 100, perform system configuration: Turn on the device power supply, set the output of the femtosecond laser (1), set the parametric amplifier (3) to output light with a corresponding wavelength as the excitation light of the test system, place the sample at the sample placement position on the sample chamber module (VI), and set the imaging system scanning parameters; Step 200, the industrial control computer (25) initializes the counter (24), the delay line platform module (II), the excitation light chopping module (IV), and the detection light detector (23); the industrial control computer (25) controls the counter (24) to receive the synchronization signal A of the femtosecond laser (1), the frequency of the synchronization signal A is f, and generates a chopper trigger signal B with a frequency of f / 2 according to this synchronization signal A, and outputs it to the chopper (14) to achieve excitation light pumping excitation; Step 300, the industrial control computer (25) controls the system to perform ultrafast pump - probe transient absorption imaging on the sample; the step 300 includes the following steps from step 301 to step 307: Step 301, the femtosecond laser (1) outputs femtosecond pulsed laser, which is split by the beam splitter (2), and a part of the light enters the parametric amplifier (3) as the excitation light; the other part of the light, which is the fundamental frequency light of the detection pulsed light, is output to the delay line platform module (II); Step 302: The delay line platform module (II) controls the optical path of the fundamental frequency light of the detection pulsed light to make the detection light irradiate the sample with a delay relative to the excitation light; Step 303: Convert the fundamental frequency light of the detection pulsed light output by the delay line platform module (II) into detection white light; Step 304: Optically chop the excitation light output by the parametric amplifier (3) to form pump excitation light; Step 305: The beam combining and splitting plate (17) transmits 50% of the detection white light and reflects 50% of the pump excitation light, making the detection white light and the pump excitation light in a coaxial and collinear state to synthesize combined light; The spot homogenization device (18) performs spot homogenization processing on the combined light; Step 306: The first objective lens (19) realizes surface excitation and surface detection of the combined light on the sample (20). After the light passes through the sample (20), the second objective lens (21) with the same focal length collects the light to make the detection white light and the pump excitation light become parallel light again; The lens (22) focuses the light; Step 307: The detection light detector (23) collects the light focused by the lens (22); Step 400: The industrial control computer (25) controls the start of scanning. The industrial control computer (25) controls the delay line platform module (II) to move according to the scanning parameters set in Step 300. After stabilizing at each moved point, the industrial control computer (25) controls the counter (24) to generate a detection light detector trigger signal C with a frequency of f according to signal B and output it to the detection light detector (23) to control the detection light detector (23) to perform scanning, obtaining the data of the excited state transmitted light intensity and the unexcited state transmitted light intensity at each delay moment, and further obtaining the transient absorption signal; Step 500: Record the transient absorption information, delay information, and imaging pixel information as the final system data and save them.

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