A measuring device for transient absorption spectroscopy under near-field conditions

Abstract

The present application relates to a kind of transient absorption spectrum measuring devices based on near-field condition, wherein probe light is injected into near-field optical scanning microscope system after passing through probe beam expander assembly and probe attenuator assembly, pump light is injected into near-field optical scanning microscope system after passing through chopper, pump beam expander assembly, pump attenuator assembly and pump light delay assembly, near-field optical scanning microscope system includes upper objective lens, scanning probe, sample carrier, lower objective lens, near-field beam splitter, near-field filter assembly and convex lens in turn along probe light path, pump light forms the path direction opposite to probe light after being reflected by near-field beam splitter, and is focused on sample after being injected into lower objective lens, probe light is input into spectrometer by fiber coupler after being emitted by convex lens.The present application can accurately capture the transport, dissipation and dynamic change of carrier in nanoscale structure under the joint action of ultrafast time resolution and ultra-high spatial resolution.

Description

Technical Field

[0001] This invention relates to the field of transient absorption spectroscopy measurement technology, specifically a transient absorption spectroscopy measurement device based on near-field conditions. Background Technology

[0002] Carrier transport and relaxation are crucial topics in semiconductor physics and materials science. Carrier mobility and transport distance play a decisive role in modern electronic devices, such as computer processors and solar cells. However, carrier transport and dissipation at the nanoscale often occur in ultrafast timeframes, such as picoseconds or even femtoseconds. To study these phenomena, scientists need measurement techniques with both high temporal and spatial resolution, and transient absorption spectroscopy is one effective method for this purpose.

[0003] Transient absorption spectroscopy is an ultrafast laser-pumped detection technique widely used to study the energy level structure and energy relaxation processes of matter in excited states. This technique excites electrons in a sample to higher energy levels using a pump laser, and then observes the absorption changes as the sample returns to the ground state at different time intervals by probing the laser, thus precisely capturing the instantaneous dynamic behavior of matter.

[0004] With the maturation of femtosecond laser technology, transient absorption spectroscopy has achieved significant improvements in temporal resolution. For example, current research allows scientists to observe ultrafast dynamics in materials on femtosecond to picosecond timescales. However, in transient absorption spectroscopy, in addition to high temporal resolution, high spatial resolution is also crucial, especially when the research involves nanoscale structures. Traditional micro-area transient absorption spectroscopy systems typically rely on microscope objectives to achieve micrometer-level spatial resolution, which is insufficient for detecting fine nanoscale structures.

[0005] With the development of technology, near-field optical scanning microscopy (SNOM) has provided a new research path to break through the traditional optical diffraction limit. Unlike traditional microscopes that focus light beams through lenses, SNOM achieves scanning imaging through the principle of atomic force microscopy (AFM). It uses a hollow scanning probe to couple probe light into the sample. The spatial resolution of this method is mainly determined by the tip aperture rather than the wavelength of light, thus breaking through the diffraction limit and achieving ultra-high spatial resolution at the nanometer level.

[0006] However, there is no precedent in the existing technology for combining transient absorption spectroscopy with SNOM technology. Currently, other methods are mainly used to ensure the spatial resolution of transient absorption spectroscopy measurements. For example, patent CN113281278B discloses a fast ultra-high resolution transient absorption spectroscopy measurement device and method. The device includes a mode-locked fiber optic comb system, an optical power amplification unit, a nonlinear frequency conversion unit, and a dual asynchronous optical sampling unit. The mode-locked fiber optic comb system is used to generate pump light, probe light, and local oscillator light. The nonlinear frequency conversion unit uses continuous spectrum technology to realize the generation of comb frequency that is continuously extended over a wide spectrum. The dual asynchronous optical sampling unit is used to perform dual asynchronous optical sampling of pump light and probe light, and local oscillator light and pump light and probe light passing through the sample. This device aims to improve the acquisition speed of transient spectral signals by sampling between the pump light and the probe light, and between the probe light and the local oscillator light without any mechanical delay. The transient absorption spectral signal of this device is obtained by a coherent detection process to significantly improve the spectral signal-to-noise ratio. The time step of the device for measuring the spectral signal can be flexibly and quickly adjusted by controlling the repetition frequency difference between the pump light comb and the probe light comb. Through the above measures, this device can achieve high-precision and rapid measurement of ultrafast time-resolved amplitude and phase spectra with a wide spectral range and spatial resolution. Summary of the Invention

[0007] The purpose of this invention is to provide a transient absorption spectroscopy measurement device based on near-field conditions. It combines near-field optical scanning microscopy system technology with femtosecond transient absorption spectroscopy technology to achieve ultra-high spatial resolution. Furthermore, under the combined effect of ultra-fast temporal resolution and ultra-high spatial resolution, it can accurately capture the transport, dissipation and dynamic changes of charge carriers in nanoscale structures.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A transient absorption spectroscopy measurement device based on near-field conditions includes a femtosecond laser and a near-field optical scanning microscope system. The laser emitted by the femtosecond laser is split into a probe beam and a pump beam by a beam splitter. The probe beam passes sequentially through a probe beam expander assembly and a probe attenuator assembly before entering the near-field optical scanning microscope system. The pump beam passes sequentially through a chopper, a pump beam expander assembly, a pump attenuator assembly, and a pump beam delay assembly before entering the near-field optical scanning microscope system. The near-field optical scanning microscope system includes an upper objective lens, a scanning probe, a sample stage, a lower objective lens, a near-field beam splitter, a near-field filter assembly, and a convex lens arranged sequentially along the probe beam path. The upper and lower objective lenses are symmetrically arranged. The scanning probe has nanopores for the probe beam to pass through. The pump beam is reflected by the near-field beam splitter to form a path direction opposite to the probe beam and finally enters the lower objective lens and is focused on the sample on the sample stage. The probe beam exits through the convex lens and is input into a spectrometer via an optical fiber coupler.

[0010] The laser emitted by the femtosecond laser is split into two laser beams by a beam splitter. One laser beam is converted into a wavelength-tunable probe beam by a first optical parametric amplifier, and the other laser beam is converted into a wavelength-tunable pump beam by a second optical parametric amplifier.

[0011] A first detection aperture is provided between the detection beam expander assembly and the detection attenuator assembly, and a second detection aperture is provided on the side of the detection attenuator assembly away from the detection beam expander assembly.

[0012] The probe light emitted from the second probe aperture enters a probe light path limiting component, which includes multiple optical path reflectors. The probe light is reflected sequentially by each optical path reflector before entering the near-field optical scanning microscope system.

[0013] The pulse frequency of the pump light is modulated by the chopper to half the output frequency of the femtosecond laser.

[0014] The pump light delay assembly includes a movable right-angle retroreflector and multiple delay mirrors, wherein the probe light is reflected by the delay mirror on one side and then enters the right-angle retroreflector, while the probe light emitted from the right-angle retroreflector is reflected by the delay mirror on the other side and then emitted.

[0015] The pump light is output from the pump light delay component and then passes through a pump aperture.

[0016] The near-field optical scanning microscope system includes multiple near-field mirrors. The probe light is reflected by the first near-field mirror and enters the upper objective lens. After passing through the scanning probe, sample stage, and lower objective lens in sequence, it is reflected by the second and third near-field mirrors in sequence and enters the near-field beam splitter. The probe light passes through the near-field beam splitter and near-field filter assembly in sequence and is reflected by the fourth near-field mirror and enters the convex lens. The pump light is reflected by the near-field beam splitter, the third near-field mirror, and the second near-field mirror in sequence and enters the lower objective lens.

[0017] The sample support stage is a piezoelectric moving stage.

[0018] The spectrometer converts the transient absorption signal into an electrical signal and transmits it to the industrial control computer. The repetition rate signal of the femtosecond laser is transmitted to a timing module, and after being down-processed by the timing module, it is transmitted to the chopper and the spectrometer respectively.

[0019] The advantages and positive effects of this invention are as follows:

[0020] 1. This invention combines near-field optical scanning microscope system technology with femtosecond transient absorption spectroscopy technology, and achieves ultra-high spatial resolution (60-150nm) through the nanopores of the scanning probe. Furthermore, with the combined effect of ultrafast temporal resolution and ultra-high spatial resolution, this invention can accurately capture the transport, dissipation and dynamic changes of charge carriers in nanoscale structures.

[0021] 2. The present invention places the laser delay component on the pump light path, which can avoid the influence on the probe light, thereby ensuring that the probe light coupled into the nanopore of the scanning probe has sufficiently high stability.

[0022] 3. This invention can achieve ultrafast temporal resolution and ultra-high spatial resolution using only pump light and probe light. Compared with existing technologies (such as patent CN113281278B), the control and processing process of this invention can be further simplified. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention.

[0024] Figure 2 for Figure 1 A schematic diagram of a mid-to-near field optical scanning microscope system.

[0025] Figure 3 This is a schematic diagram showing the location of the values ​​for isolated MoS2 grains in a single-layer MoS2 structure in one application example of the present invention.

[0026] Figure 4 For the present invention to Figure 3 The diagram shows the exciton dynamics decay curves obtained by measuring the points in each value range shown.

[0027] In this designation, 1 is a femtosecond laser, 101 is a beam splitter, 2 is a probe beam, 201 is a first probe mirror, 202 is a first optical parametric amplifier, 203 is a second probe mirror, 204 is a probe beam expander assembly, 205 is a first probe aperture, 206 is a probe attenuator assembly, 207 is a second probe aperture, 208 is a probe beam path limiting assembly, 2081 is an optical path mirror, 3 is a pump beam, 301 is a second optical parametric amplifier, 302 is a first pump mirror, 303 is a chopper, 304 is a second pump mirror, 305 is a pump beam expander assembly, 306 is a pump attenuator assembly, and 307 is a pump beam. The components are: 3071 (delay mirror), 3072 (right-angle mirror), 308 (pump stop), 309 (fourth pump mirror), 310 (third pump mirror), 4 (near-field optical scanning microscope system), 401 (first near-field mirror), 402 (upper objective), 403 (scanning probe), 404 (sample stage), 405 (lower objective), 406 (second near-field mirror), 407 (third near-field mirror), 408 (near-field beam splitter), 409 (near-field filter assembly), 410 (fourth near-field mirror), 411 (convex lens), 5 (industrial control computer), 6 (fiber optic coupler), 7 (spectrometer), and 8 (timing module). Detailed Implementation

[0028] The invention will now be described in further detail with reference to the accompanying drawings.

[0029] like Figures 1-2 As shown, the present invention includes a femtosecond laser 1 and a near-field optical scanning microscope system 4. The laser emitted by the femtosecond laser 1 is split into two beams by a beam splitter 101. One beam is amplified by a first optical parametric amplifier 202 to form a wavelength-tunable probe beam 2, and the other beam is amplified by a second optical parametric amplifier 301 to form a wavelength-tunable pump beam 3. The probe beam 2 passes sequentially through a probe beam expander 204 and a probe attenuator 206 before entering the near-field optical scanning microscope system 4. The pump beam 3 passes sequentially through a chopper 303, a pump beam expander 305, a pump attenuator 306, and a pump delay 307 before entering the near-field optical scanning microscope system 4. Figure 2As shown, the near-field optical scanning microscope system 4 includes an upper objective lens 402, a scanning probe 403, a sample stage 404, a lower objective lens 405, a near-field beam splitter 408, a near-field filter assembly 409, and a convex lens 411 arranged sequentially along the path of the probe light 2. The upper objective lens 402 and the lower objective lens 405 are symmetrically arranged. The scanning probe 403 is provided with nanopores for the probe light 2 to pass through. The pump light 3 is reflected by the near-field beam splitter 408 to form a path direction opposite to that of the probe light 2, and finally enters the lower objective lens 405 and is focused on the sample on the sample stage 404 to excite the sample. The probe light 2 is emitted from the convex lens 411 and then enters the spectrometer 7 through the fiber optic coupler 6.

[0030] like Figure 1 As shown, in this embodiment, the femtosecond laser 1 is used to output pulsed light with a pulse width of 230 fs, while the probe light 2 and pump light 3, after being amplified by the first optical parametric amplifier 202 and the second optical parametric amplifier 301, have wavelengths ranging from 300 to 3000 nm. The optical parametric amplifiers are well-known in the art and are commercially available products.

[0031] like Figure 1 As shown, in this embodiment, a laser beam emitted by the femtosecond laser 1 is reflected by the first detector mirror 201 and then enters the first optical parametric amplifier 202 to form a detector beam 2. The detector beam 2 is reflected by the second detector mirror 203 and then passes sequentially through the detector beam expander assembly 204 and the detector attenuator assembly 206. The detector beam expander assembly 204 is used to expand and collimate the detector beam 2, and the detector attenuator assembly 206 is used to adjust the intensity of the detector beam 2 to meet experimental requirements. In this embodiment, the detector beam expander assembly 204 includes multiple beam expander lenses, and the detector attenuator assembly 206 includes multiple attenuators.

[0032] like Figure 1 As shown, in this embodiment, a first detection aperture 205 is provided between the detection beam expander component 204 and the detection attenuator component 206, and a second detection aperture 207 is provided on the side of the detection attenuator component 206 away from the detection beam expander component 204. The first detection aperture 205 and the second detection aperture 207 are used to optimize the shape of the detection beam 2 and improve the beam quality.

[0033] like Figure 1 As shown, in this embodiment, the probe light 2 passes through a probe light path limiting component 208 before entering the near-field optical scanning microscope system 4. In this embodiment, the probe light path limiting component 208 includes multiple optical path reflectors 2081. The probe light 2 is reflected sequentially by each optical path reflector 2081 and finally enters the near-field optical scanning microscope system 4 to detect the transient absorption signal of the sample.

[0034] like Figure 1 As shown, in this embodiment, another laser beam emitted by the femtosecond laser 1 is amplified by the second optical parametric amplifier 301 to form pump light 3. The pump light 3 is first reflected by the first pump mirror 302 and then enters the chopper 303. In this embodiment, the chopper 303 operates at a frequency of 500Hz. Its function is to modulate the pulse frequency of the pump light 3 to half the output frequency of the femtosecond laser 1 to synchronize with the probe light 2 signal. The chopper 303 is a well-known technology in the art and is a commercially available product. The pump light 3 emitted from the chopper 303 is reflected by the second pump mirror 304 and then sequentially passes through the pump beam expander assembly 305 and the pump attenuator assembly 306. The pump beam expander assembly 305 includes multiple beam expanders to expand and collimate the pump light 3, thereby ensuring that the pump light 3 can effectively cover the sample under test. The pump attenuator assembly 306 includes multiple attenuators to adjust the intensity of the pump light to meet experimental requirements.

[0035] like Figure 1 As shown, pump light 3 is emitted from pump attenuator assembly 306 and reflected by third pump reflector 310 before entering pump light delay assembly 307. In this embodiment, pump light delay assembly 307 includes a right-angle retroreflector 3072 and multiple delay reflectors 3071. Probe light 2 is reflected by delay reflector 3071 on one side and enters right-angle retroreflector 3072, while probe light 2 emitted from right-angle retroreflector 3072 is reflected by delay reflector 3071 on the other side and exits. Pump light delay assembly 307 is used to adjust the optical path difference between pump light 3 and probe light 2 to measure transient absorption signals under different time delay conditions. This invention achieves precise optical path control by controlling the precise displacement of right-angle retroreflector 3072.

[0036] like Figure 1 As shown, after being output by the pump light delay component 307, the pump light 3 first passes through the pump aperture 308, and then is reflected by the fourth pump mirror 309 into the near-field optical scanning microscope system 4. The pump aperture 308 is used to optimize the spot shape of the pump light 3 and improve the beam quality.

[0037] like Figure 2As shown, in this embodiment, the near-field optical scanning microscope system 4 further includes multiple near-field mirrors. The probe light 2 is reflected by the first near-field mirror 401 and enters the upper objective lens 402. After passing through the scanning probe 403, the sample stage 404, and the lower objective lens 405 in sequence, it is reflected by the second near-field mirror 406 and the third near-field mirror 407 in sequence and enters the near-field beam splitter 408. The probe light 2 passes through the near-field beam splitter 408 and the near-field filter assembly 409 in sequence and is reflected by the fourth near-field mirror 410 and enters the convex lens 411. The pump light 3 is reflected by the near-field beam splitter 408, the third near-field mirror 407, and the second near-field mirror 406 in sequence and enters the lower objective lens 405.

[0038] The scanning probe 403 is provided with nanopores through which the probe light 2 passes. The spatial resolution of the present invention depends on the size of the nanopores. In this embodiment, there are three specifications: 60nm, 90nm, and 150nm. In addition, the reason why the pump light delay component 307 is placed on the pump light 3 path is that the probe light 2 coupled into the scanning probe 403 needs to have extremely high stability. Placing the laser delay component on the pump light 3 path can avoid its influence on the stability of the probe light 2.

[0039] like Figure 2 As shown, in this embodiment, the sample support stage 404 is a piezoelectric displacement stage. This piezoelectric displacement stage can be used to precisely control the minute displacement of the sample to ensure scanning imaging at different positions. The piezoelectric displacement stage is a technology known in the art.

[0040] like Figure 1 As shown, the present invention also includes an industrial control computer 5, an optical fiber coupler 6, a spectrometer 7, and a timing module 8. The probe light 2, emitted from the convex lens 411, passes through the optical fiber coupler 6 and is input into the spectrometer 7. The spectrometer 7 converts the transient absorption signal into an electrical signal and transmits it to the industrial control computer 5 for data processing. The repetition rate signal of the femtosecond laser 1 is transmitted to the timing module 8, and the repetition rate output control software in the timing module 8 reduces the output repetition rate to half of the laser repetition rate. Then, it is transmitted to the chopper 303 and the spectrometer 7 respectively to achieve timing synchronization. The industrial control computer 5, optical fiber coupler 6, spectrometer 7, and timing module 8 are all technologies known in the art and are commercially available products.

[0041] The working principle of this invention is as follows:

[0042] like Figure 1As shown, during operation, the laser emitted by the femtosecond laser 1 is split into two laser beams by the beam splitter 101. These two beams are then amplified by the first optical parametric amplifier 202 and the second optical parametric amplifier 301, respectively, to form a probe beam 2 and a pump beam 3 with adjustable output wavelengths. The probe beam 2 is expanded and collimated by the probe beam expander assembly 204 and its intensity is adjusted by the probe attenuator assembly 206 before entering the near-field optical scanning microscope system 4. The pump beam 3 is first adjusted by the chopper 303 to half the output frequency of the femtosecond laser 1 to synchronize with the probe beam 2 signal, and then... After the pump beam expander assembly 305 expands and collimates the beam, and the pump attenuator assembly 306 adjusts the intensity, the light enters the pump light delay assembly 307. The pump light delay assembly 307 is used to adjust the optical path difference between the pump light 3 and the probe light 2 so as to measure the transient absorption signal under different time delay conditions. At the same time, since the probe light 2 of the present invention needs to pass through the nanopores on the scanning probe 403 to irradiate the sample after entering the near-field optical scanning microscope system 4, the probe light 2 needs to have extremely high stability. Therefore, the present invention sets the laser delay assembly on the path of the pump light 3 to ensure the stability of the probe light 2.

[0043] And such Figure 2 As shown, after the pump light 3 enters the near-field optical scanning microscope system 4, it is first reflected by the near-field beam splitter 408 to form a path opposite to that of the probe light 2. It is then reflected sequentially by the third near-field mirror 407 and the second near-field mirror 406 before entering the lower objective lens 405 and focusing on the sample on the sample stage 404 to excite the sample. The probe light 2, after entering the near-field optical scanning microscope system 4, sequentially passes through the upper objective lens 402, scanning probe 403, sample stage 404, lower objective lens 405, near-field beam splitter 408, near-field filter assembly 409, and convex lens 411. It is then input into the spectrometer 7 via the fiber optic coupler 6. The spectrometer 7 converts the transient absorption signal into an electrical signal and transmits it to the operating system. The controller 5 performs data processing. During the above process, the nanopores on the scanning probe 403 couple the probe light 2 to a local area on the sample surface to achieve nanoscale spatial resolution. At the same time, the sample support stage 404 is a piezoelectric potential moving stage that can be used to precisely control the tiny displacement of the sample to ensure scanning imaging at different positions. The near-field filter assembly 409 is used to filter stray light from the pump light 3 or other unnecessary light signals mixed in the probe light 2 to ensure the purity of the probe light 2. In addition, the repetition rate signal of the femtosecond laser 1 is transmitted to the timing module 8, and the repetition rate output control software in the timing module 8 reduces the output repetition rate to half of the laser repetition rate. Then, it is transmitted to the chopper 303 and the spectrometer 7 respectively to achieve timing synchronization.

[0044] This invention combines near-field optical scanning microscopy system technology with femtosecond transient absorption spectroscopy technology, achieving ultra-high spatial resolution (60-150 nm) through the nanopores of the scanning probe 403. Furthermore, with the combined effect of ultrafast temporal resolution and ultra-high spatial resolution, this invention can accurately capture the transport, dissipation, and dynamic changes of charge carriers in nanoscale structures.

[0045] The following application example further illustrates the working principle of the present invention.

[0046] Application Example 1:

[0047] This application example studies the carrier dynamics of isolated monolayer molybdenum disulfide (MoS2) grains. MoS2 is a two-dimensional semiconductor material with excellent optoelectronic properties, widely used in electronic and optoelectronic devices. Using the device of this invention, its dynamics can be characterized at the nanoscale and femtosecond timescales. Specifically:

[0048] 1. Sample preparation: The experimental sample was a monolayer of isolated molybdenum disulfide grains, which were prepared on a sapphire substrate by chemical vapor deposition (CVD) and then transferred to a glass slide with a thickness of 0.15 mm.

[0049] 2. Light Source Setup: Start femtosecond laser 1, outputting a laser with a pulse width of 230 fs. Set the wavelength of pump light 3 to 450 nm and probe light 2 to 600 nm using an optical parametric amplifier, covering the exciton absorption region of MoS2. Adjust the optical path lengths of the pump and probe lights and control their time difference to achieve ultrafast dynamic measurements.

[0050] 3. Adjustment of the near-field optical scanning microscope system: Place the monolayer MoS2 sample on the sample support stage 404 (piezoelectric displacement stage), focus the pump light 3 onto the sample through the inverted lower objective lens 405 and excite the charge carriers, and couple the probe light 2 into the nanopores of the scanning probe 403 through the upper objective lens 402 to achieve measurement of the local area of ​​the sample.

[0051] 4. Measurement Process: Pump light 3 excites charge carriers in MoS2, and probe light 2 irradiates the sample under different delay times, recording its transient absorption changes. The device of this invention adjusts the delay time using the pump light delay component 307 to obtain signal intensities at different time points. By controlling the piezoelectric displacement stage to move different regions of the probe sample, the local dynamic characteristics of each region of the grain are measured. In this application example, different value points are shown in the following regions: Figure 3 As shown, the exciton dynamics decay curves for different value points are as follows: Figure 4 As shown.

[0052] This application example successfully achieved ultrafast dynamic characterization of isolated monolayer MoS2 grains at the nanoscale through transient absorption spectroscopy measurements under near-field conditions.

Claims

1. A transient absorption spectroscopy measurement device based on near-field conditions, characterized in that: The system includes a femtosecond laser (1) and a near-field optical scanning microscope system (4). The laser emitted by the femtosecond laser (1) is split into a probe beam (2) and a pump beam (3) by a beam splitter (101). The probe beam (2) passes sequentially through a probe beam expander (204) and a probe attenuator assembly (206) before entering the near-field optical scanning microscope system (4). The pump beam (3) passes sequentially through a chopper (303), a pump beam expander (305), a pump attenuator assembly (306), and a pump beam delay assembly (307) before entering the near-field optical scanning microscope system (4). The near-field optical scanning microscope system (4) includes an upper objective lens arranged sequentially along the path of the probe beam (2). The instrument comprises an upper objective (402), a scanning probe (403), a sample stage (404), a lower objective (405), a near-field beam splitter (408), a near-field filter assembly (409), and a convex lens (411). The upper objective (402) and the lower objective (405) are symmetrically arranged. The scanning probe (403) has nanopores for the probe light (2) to pass through. The pump light (3) is reflected by the near-field beam splitter (408) to form a path direction opposite to that of the probe light (2), and finally enters the lower objective (405) and is focused on the sample on the sample stage (404). The probe light (2) is emitted from the convex lens (411) and enters the spectrometer (7) through the fiber optic coupler (6).

2. The transient absorption spectroscopy measurement device based on near-field conditions according to claim 1, characterized in that: The laser emitted by the femtosecond laser (1) is split into two laser beams by a beam splitter (101). One laser beam is converted into a wavelength-tunable probe beam (2) by a first optical parametric amplifier (202), and the other laser beam is converted into a wavelength-tunable pump beam (3) by a second optical parametric amplifier (301).

3. The transient absorption spectroscopy measurement device based on near-field conditions according to claim 1, characterized in that: A first detection aperture (205) is provided between the detection beam expander assembly (204) and the detection attenuator assembly (206), and a second detection aperture (207) is provided on the side of the detection attenuator assembly (206) away from the detection beam expander assembly (204).

4. The transient absorption spectroscopy measurement device based on near-field conditions according to claim 3, characterized in that: The probe light (2) emitted from the second probe aperture (207) enters a probe light path limiting component (208), which includes multiple optical path reflectors (2081). The probe light (2) is reflected by each optical path reflector (2081) in sequence and then enters the near-field optical scanning microscope system (4).

5. The transient absorption spectroscopy measurement device based on near-field conditions according to claim 1, characterized in that: The pulse frequency of the pump light (3) is modulated by the chopper (303) to half the output frequency of the femtosecond laser (1).

6. The transient absorption spectroscopy measurement device based on near-field conditions according to claim 1, characterized in that: The pump light delay assembly (307) includes a movable right-angle retroreflector (3072) and a plurality of delay mirrors (3071), wherein the probe light (2) is reflected by the delay mirror (3071) on one side and then enters the right-angle retroreflector (3072), while the probe light (2) emitted from the right-angle retroreflector (3072) is reflected by the delay mirror (3071) on the other side and then emitted.

7. The transient absorption spectroscopy measurement device based on near-field conditions according to claim 6, characterized in that: The pump light (3) is output from the pump light delay component (307) and then passes through a pump aperture (308).

8. The transient absorption spectroscopy measurement device based on near-field conditions according to claim 1, characterized in that: The near-field optical scanning microscope system (4) includes multiple near-field mirrors. The probe light (2) is reflected by the first near-field mirror (401) and enters the upper objective lens (402). It then passes through the scanning probe (403), the sample stage (404), and the lower objective lens (405) in sequence. After passing through the second near-field mirror (406) and the third near-field mirror (407), it enters the near-field beam splitter (408). The probe light (2) passes through the near-field beam splitter (408) and the near-field filter assembly (409) in sequence and is reflected by the fourth near-field mirror (410) into the convex lens (411). The pump light (3) is reflected by the near-field beam splitter (408), the third near-field mirror (407), and the second near-field mirror (406) in sequence and enters the lower objective lens (405).

9. The transient absorption spectroscopy measurement device based on near-field conditions according to claim 1, characterized in that: The sample support stage (404) is a piezoelectric moving stage.

10. The transient absorption spectroscopy measurement device based on near-field conditions according to claim 1, characterized in that: The spectrometer (7) converts the transient absorption signal into an electrical signal and transmits it to the industrial control computer (5). The repetition rate signal of the femtosecond laser (1) is transmitted to a timing module (8) and then transmitted to the chopper (303) and the spectrometer (7) respectively after being down-processed by the timing module (8).

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