Nanoscale infrared photothermal imaging system and imaging method

Abstract

The invention relates to a nanoscale infrared photothermal imaging system and an imaging method. The method comprises the following steps: introducing lasers with different wavelengths into a scanning noise infrared near-field optical microscope system; a laser spot is limited to be less than 10 microns, and rough calibration of the probe and the laser spot can be carried out; dynamically and continuously tuning the power of the introduced laser; and obtaining a nano-scale heat distribution image of the sample under laser excitation. The laser with different wavelengths can be introduced into a scanning noise infrared near-field optical microscope system, the power of the laser with the corresponding wavelength can be dynamically and continuously tuned, and a nanoscale photo-thermal distribution image of a sample under excitation of the laser with the tunable wavelength and power can be obtained.

Description

Technical Field

[0001] This invention relates to the field of near-field optical characterization, and more particularly to a nanoscale infrared photothermal imaging system and imaging method. Background Technology

[0002] The photothermal effect refers to the physical phenomenon where a substance absorbs light energy and converts it into heat energy through a non-radiative relaxation process, thereby causing a local increase in electron and lattice temperature. This effect is widely used in photothermal imaging, photothermal therapy, and thermophysical property measurement. Photothermal microscopy, based on the photothermal effect, can achieve imaging resolution exceeding the traditional far-field diffraction limit (micrometer scale) in the infrared band. Currently, two main detection methods are used: 1. Infrared light excites the sample, causing localized thermal expansion of the material, and photothermal imaging is achieved by detecting surface deformation using atomic force microscopy; 2. Infrared light is used to locally heat the material, and photothermal imaging is achieved by using visible light as the probe light in a far-field optical method to detect changes in visible light reflectivity. However, neither of these methods can directly measure and image the thermal radiation signal generated by the photothermal effect, which limits the accurate measurement of temperature changes caused by the photothermal effect and the exploration of near-field thermal radiation patterns.

[0003] Scanning noise infrared near-field optical microscopes (SMILEs) based on near-field optics principles can directly detect near-field thermal radiation signals from samples and perform high-resolution imaging. However, existing SMILEs lack integrated laser excitation systems, thus preventing the acquisition of thermal radiation signals under laser excitation conditions, which limits the solution to the aforementioned photothermal problems. Furthermore, the lack of laser excitation methods restricts research to materials with good electrical conductivity, limiting the exploration of interactions to electron-electron and electron-phonon processes. Meanwhile, many optoelectronic devices require consideration of electron-optical field coupling at the micro- and nano-scale. Introducing laser excitation can not only overcome this limitation but also introduce new interactions such as light-electron and light-phonon interactions, enriching the research scope and potentially revealing a series of novel physical phenomena. Summary of the Invention

[0004] The purpose of this invention is to provide a nanoscale infrared photothermal imaging system and imaging method, which solves the problem that existing technologies cannot directly measure and image the thermal radiation signals generated by the photothermal effect, thus limiting the accurate measurement of temperature changes caused by the photothermal effect and the exploration of the laws of near-field thermal radiation.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A nanoscale infrared photothermal imaging system, characterized in that: it includes a scanning noise infrared near-field optical microscope and a laser excitation device; the laser excitation device includes a free-space light-coupled to fiber optic module and a laser-introduced probe system module;

[0007] The free-space light-coupled fiber module includes a laser with adjustable power, a chopper, a mirror group with adjustable angle, a first objective lens with three-dimensional adjustment, and a first fiber collimator with three-dimensional adjustment, all mounted on the same optical breadboard, as well as a single-mode fiber adapted to the laser wavelength.

[0008] The first objective lens is used to finely adjust its position to focus the laser onto the end face of the single-mode fiber; the first fiber collimator is used to finely adjust the position of the single-mode fiber to couple the focused laser into the single-mode fiber.

[0009] The reflector assembly consists of a first reflector and a second reflector. After the laser beam modulated by the chopper enters the first reflector, it is reflected into the second reflector. The second reflector reflects the laser beam into the center of the back focal plane of the first objective lens. The first and second reflectors adjust their angles according to the wavelength of the laser beam.

[0010] The laser-introduced probe system module includes a four-dimensional adjustment stage, a second objective lens, a second fiber collimator, and a converging lens; the four-dimensional adjustment stage consists of a three-dimensional displacement stage and a rotary displacement stage, with the rotary displacement stage set on the three-dimensional displacement stage.

[0011] The second fiber collimator is connected to the first fiber collimator via a single-mode fiber; the converging lens focuses the laser onto the back focal plane of the second objective; the second objective focuses the laser onto the probe of the scanning noise infrared near-field optical microscope; after fine adjustments by the four-dimensional adjustment stage, the focused laser spot is moved to the tip of the probe.

[0012] The four-dimensional adjustment stage and the scanning noise infrared near-field optical microscope are set on the same optical platform.

[0013] The free-space light coupling to the fiber optic module also includes a three-dimensional fine displacement stage, a two-dimensional fine displacement stage, and a Z-axis fine displacement stage; the first objective lens is set on the three-dimensional fine displacement stage, the first fiber collimator is set on the two-dimensional fine displacement stage, and the two-dimensional fine displacement stage is set on the Z-axis fine displacement stage.

[0014] The laser-introduced probe system module also includes a cage-type support and an optical strut, with the cage-type support consisting of the cage-type strut.

[0015] The second fiber collimator, converging lens, and second objective lens are sequentially arranged inside a cage-like support. The cage-like support is set on a rotating stage, which is mounted on a three-dimensional stage via an optical support rod. The three-dimensional stage and the rotating stage are adjusted to converge the laser onto the probe of the scanning noise infrared near-field optical microscope.

[0016] The cage support consists of four cage-type support rods.

[0017] The imaging method of the aforementioned nanoscale infrared photothermal imaging system comprises the following specific steps:

[0018] S1, mount the sample to be tested on the fine three-dimensional displacement stage of the scanning noise infrared near-field optical microscope;

[0019] S2, a low-temperature environment was established using a low-temperature Dewar oscilloscope with a scanning noise infrared near-field optical microscope;

[0020] S3, connect the electrical test channel of the scanning noise infrared near-field optical microscope and read the electrical characteristics of the detector in the cryogenic Dewar; if the electrical characteristics of the detector in the cryogenic Dewar are normal, proceed to step S4; if the electrical characteristics of the detector in the cryogenic Dewar are abnormal, jump to step S2, let the cryogenic Dewar return to room temperature naturally, and then cool it again.

[0021] S4, laser introduction;

[0022] Turn on the laser and chopper, and use free space light coupling to convert the output laser into a fiber laser by connecting it to the fiber module. Connect the fiber laser to the laser introduction probe system module so that the fiber laser is focused onto the probe of the scanning noise infrared near-field optical microscope. Finely adjust the four-dimensional adjustment stage to move the focused laser spot to the probe tip.

[0023] S5, turn on the light source of the scanning noise infrared near-field optical microscope, use its optical CCD imaging system to observe the relative position of the sample and the laser spot, and use the four-dimensional adjustment stage of the laser-introduced probe system module to adjust the laser spot to irradiate the detection position of the sample to be tested.

[0024] S6, laser-excited probe scanning imaging;

[0025] Using a scanning noise near-field optical microscope module, the thermal distribution of the sample under test is scanned and imaged under laser excitation;

[0026] S7, disconnect the instrument, turn off the light source, remove the sample, and the measurement is complete.

[0027] The specific steps of S4 are as follows:

[0028] S401, turn on the laser and chopper, adjust the position of the laser beam so that the laser spot illuminates the center of the first and second reflectors;

[0029] S402, using the first and second reflecting mirrors to reflect the emitted laser to the center of the back focal plane of the first objective lens that can be adjusted in three dimensions;

[0030] S403, finely adjust the first objective lens so that the laser spot converged by the first objective lens illuminates the center of the first fiber collimator that can be adjusted in three dimensions.

[0031] S404, finely adjust the position of the first fiber collimator to maximize the coupling power between the converging laser and the single-mode fiber.

[0032] The specific steps in S5 for adjusting the position of the laser spot on the sample using the four-dimensional adjustment stage of the laser-introduced probe system module are as follows:

[0033] S501, the laser focused onto the first fiber collimator is introduced into the laser introduction probe system module through a single-mode fiber of the corresponding wavelength;

[0034] S502, adjust the converging lens to focus the laser beam onto the center of the back focal plane of the second objective lens;

[0035] S503, by adjusting the three-dimensional displacement stage and the rotational displacement stage of the four-dimensional adjustment stage, the converging laser is introduced onto the probe of the scanning noise infrared near-field optical microscope.

[0036] The advantages of this invention are: 1. This invention integrates optical excitation into a scanning noise near-field optical microscope system, expanding the excitation methods for the measured sample in existing scanning noise near-field optical microscope systems, and enabling thermal distribution imaging of the measured sample using optical excitation; 2. This invention expands the research system, allowing the study of more materials, so that the research system is not limited to materials with good conductivity. Attached Figure Description

[0037] Figure 1 This is a simplified structural diagram of the nanoscale infrared photothermal imaging system of the present invention;

[0038] Figure 2 This is a flowchart of the imaging method of the nanoscale infrared photothermal imaging system of the present invention;

[0039] Figure 3 This is a schematic diagram of the structure of the sample to be tested in an embodiment;

[0040] Figure 4 Yes Figure 3 A schematic diagram of the test sample being tested;

[0041] Figure 5Yes Figure 3 A comparison of far-field one-dimensional scanning and AFM scanning of the metal structure of the sample under test;

[0042] Figure 6 Yes Figure 3 A comparison of one-dimensional scanning and near-field scanning of the metal structure of the sample under test using AFM;

[0043] Figure 7 Yes Figure 3 The test results of the near-field signal of the sample under test as a function of probe height;

[0044] Figure 8 It is the near-field imaging result of a laser-excited scanning noise infrared near-field optical microscope.

[0045] In the diagram: 1-Laser, 2-Chopper, 3-First reflecting mirror, 4-Second reflecting mirror, 5-First objective lens, 6-3D fine displacement stage, 7-First fiber collimator, 8-2D fine displacement stage, 9-Z-axis fine displacement stage, 10-Optical breadboard, 11-Single-mode fiber, 12-Second fiber collimator, 13-Converging lens, 14-Cage support, 15-Optical support, 16-3D displacement stage, 17-Rotational displacement stage, 18-Second objective lens, 19-Stage support pillar, 20-3D fine stage, 21-Probe, 22-Long-wave infrared microscope objective lens, 23-Cryogenic Dewar, 24-Electrical test window, 25-Optical CCD 3D displacement stage, 26-Displacement stage support pillar, 27-Microscope objective lens, 28-Optical CCD rotational displacement stage, 29-Optical CCD, 30-Optical platform, 31-Dewar support, 32-Evacuation valve, 33-Infusion tube connector. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings. The drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0047] To simplify the description of this embodiment, some components that are well-known to those skilled in the art but are not related to the main content of this invention may be omitted in the accompanying drawings or description. Additionally, for ease of description, some components in the drawings may be omitted, enlarged, or reduced, but these do not represent the actual product dimensions or the complete structure.

[0048] This invention discloses a nanoscale infrared photothermal imaging system, such as... Figure 1 As shown, it includes a scanning noise infrared near-field optical microscope and a laser excitation device; wherein, the laser excitation device includes a free space light coupling to an optical fiber module and a laser introduction probe system module.

[0049] The free-space light-coupled-to-fiber module converts free-space laser light into laser light confined to a single-mode fiber for propagation; the laser introduction probe system module is connected to the free-space light-coupled-to-fiber module via a single-mode fiber, focusing the laser light from the single-mode fiber into the probe system;

[0050] The free-space light coupled to the fiber optic module includes a laser 1 capable of adjusting different powers, a chopper 2, a mirror group capable of angle adjustment, a first objective lens 5 capable of three-dimensional adjustment, and a first fiber collimator 7 capable of three-dimensional adjustment, all mounted on the same optical breadboard 10, as well as a single-mode fiber 11 adapted to the laser wavelength.

[0051] Furthermore, the free-space light coupling to the fiber optic module also includes a three-dimensional fine displacement stage 6, a two-dimensional fine displacement stage 8, and a Z-axis fine displacement stage 9; the first objective lens 5 is mounted on the three-dimensional fine displacement stage 6, and the first objective lens 5 is adjusted in three dimensions through the three-dimensional fine displacement stage 6; the first fiber collimator 7 is mounted on the two-dimensional fine displacement stage 8, and the two-dimensional fine displacement stage 8 is mounted on the Z-axis fine displacement stage 9, and the first fiber collimator 7 achieves three-dimensional adjustment through the cooperative adjustment of the two-dimensional fine displacement stage 8 and the Z-axis fine displacement stage 9.

[0052] The first objective lens 5 is used to finely adjust its position via a three-dimensional fine displacement stage 6 to focus the laser onto the end face of the single-mode fiber 11; the first fiber collimator 7 is used to finely adjust the position of the single-mode fiber 11 through the coordinated adjustment of a two-dimensional fine displacement stage 8 and a Z-axis fine displacement stage 9 to couple the focused laser into the single-mode fiber 11.

[0053] The reflector assembly consists of a first reflector 3 and a second reflector 4, which are positioned opposite each other at an angle that can be adjusted. Laser light modulated by the chopper 2 enters the first reflector 3 and is reflected into the second reflector 4, which then reflects the laser light into the center of the back focal plane of the first objective lens 5. The angles of the first reflector 3 and the second reflector 4 are adjusted according to the wavelength of the incident laser light.

[0054] The laser-introduced probe system module includes a four-dimensional adjustment stage, a second objective lens 18, a second fiber collimator 12, and a converging lens 13; the four-dimensional adjustment stage consists of a three-dimensional displacement stage 16 and a rotary displacement stage 17; the rotary displacement stage 17 is set on the three-dimensional displacement stage 16.

[0055] Furthermore, the laser introduction probe system module also includes a cage support and an optical support rod 15; the cage support is composed of cage support rods 14, preferably, the cage support is composed of four cage support rods 14.

[0056] The second fiber collimator 12, the converging lens 13, and the second objective lens 18 are sequentially arranged in a cage-like support composed of four cage-like rods 14. The cage-like support is set on a rotary displacement stage 17, which is set on a three-dimensional displacement stage 16 via optical rods 15. The cooperation of the four-dimensional adjustment stage composed of the three-dimensional displacement stage 16 and the rotary displacement stage 17 enables the second fiber collimator 12 to be adjusted in four dimensions, thereby converging the laser onto the probe 21 of the scanning noise infrared near-field optical microscope.

[0057] The second fiber collimator 12 is connected to the first fiber collimator 7 via a single-mode fiber 11; the converging lens 13 focuses the laser onto the back focal plane of the second objective lens 18; the second objective lens 18 focuses the laser onto the probe of the scanning noise infrared near-field optical microscope; after fine adjustment by the four-dimensional adjustment stage, the focused laser spot is moved to the tip of the probe 21.

[0058] The four-dimensional adjustment stage and the scanning noise infrared near-field optical microscope are set on the same optical platform 30.

[0059] Existing scanning noise infrared near-field optical microscopes, such as Figure 1As shown, it consists of a stage support 19, a three-dimensional fine stage 20, a nanoscale probe 21, a long-wave infrared microscope objective 22, a cryogenic Dewar 23, an electrical test window 24, an optical CCD three-dimensional displacement stage 25, a displacement stage support 26, a microscope objective 27, an optical CCD rotating displacement stage 28, an optical CCD 29, a Dewar support 31, a vacuum valve 32, and an infusion tube connector 33, all mounted on an optical platform 30. The stage support 19, the optical CCD three-dimensional displacement stage 25, and the Dewar bracket 31 are mounted on the optical platform 30. The probe 21 is mounted on the three-dimensional precision stage 20. The charge-induced infrared detector is encapsulated in the cryogenic Dewar 23, which is fixed above the three-dimensional precision stage 20 by the Dewar bracket 31. The long-wave infrared microscope objective 22 is mounted upside down on the bottom of the cryogenic Dewar 23. The electrical test window 24 is mounted on the side wall of the cryogenic Dewar 23. The displacement stage support 26 is mounted on the optical CCD three-dimensional displacement stage 25. The microscope objective 27 and the optical CCD 29 are connected together. The optical CCD 29 is mounted on the rotating optical CCD rotating displacement stage 28, which is mounted on the displacement stage support 26. Before measurement, the evacuation valve 32 is opened to evacuate the compartment of the cryogenic Dewar 23. When the evacuation valve 32 is closed, a high vacuum state is maintained inside the compartment of the cryogenic Dewar 23. The cryogenic liquid can be injected into the evacuated cryogenic Dewar 23 through the infusion tube connector 33, thereby lowering the internal temperature of the cryogenic Dewar 23. After a certain period of time, the charge-induced infrared detector encapsulated in the cryogenic Dewar 23 is cooled to the cryogenic liquid temperature. The sample to be tested is mounted on the three-dimensional fine stage 20, and the light reflected from the sample is collected by the microscope objective 27. The microscopic images of the sample and the nanoscale probe 21 can be observed on the display by the optical CCD 29.

[0060] The imaging method of the nanoscale infrared photothermal imaging system described in this invention, such as... Figure 2 As shown, the specific steps are as follows:

[0061] S1. Mount the sample to be tested on the three-dimensional fine stage 20 of the scanning noise infrared near-field optical microscope.

[0062] Specifically, the sample to be tested is placed on the three-dimensional fine stage 20, and the height of the three-dimensional fine stage 20 is adjusted to the focal position of the optical microscope objective 27. At this time, a clear sample image can be observed on the monitor using the optical CCD 29.

[0063] S2, a low-temperature environment was established using a low-temperature Dewar 23 scanning noise infrared near-field optical microscope.

[0064] By using the evacuation valve 32 of the cryogenic Dewar 23, the diaphragm of the cryogenic Dewar 23 is evacuated to a vacuum. One implementation method is to first use a mechanical pump to evacuate to a negative pressure of 5 × 10⁻⁶. -2Torr, then use a molecular pump to evacuate to a negative pressure of 5 × 10⁻⁶. -5 After Torr, close the evacuation valve 32 and then shut down the molecular pump. Use the infusion connector 33 to introduce liquid nitrogen into the cryogenic Dewar 23 until liquid nitrogen overflows from the infusion connector 33; after cooling for 3 hours, slowly blow nitrogen into the infusion connector 33 and slowly blow liquid nitrogen out of the cryogenic Dewar 23 until no liquid nitrogen flows out; use the infusion connector 33 to introduce liquid helium into the cryogenic Dewar 23 until liquid helium overflows from the infusion connector 33, and then cool for half an hour.

[0065] S3 connects to the electrical test channel of the scanning noise infrared near-field optical microscope to read the electrical characteristics of the detector in the cryogenic Dewar 23; using the electrical test window 24 of the cryogenic Dewar 23, an external measuring power meter is connected to the electrical test window 24 via a PNC cable, and the electrical characteristics of the detector in the cryogenic Dewar 23 under a certain voltage are recorded using the external power meter.

[0066] If the electrical characteristics of the detector are normal, proceed to step S4; if the electrical characteristics of the detector are abnormal, jump to step S2, allow the cryogenic Dewar 23 to naturally return to room temperature, and then cool it again.

[0067] S4, laser introduction;

[0068] Turn on laser 1 and chopper 2, and convert the output laser into a fiber laser by coupling free space light to the fiber module. Connect the fiber laser to the laser introduction probe system module so that the fiber laser is focused onto the probe 21 of the scanning noise infrared near-field optical microscope. Make fine adjustments to the four-dimensional adjustment stage to move the focused laser spot to the tip of the probe 21.

[0069] The specific steps for implementation are:

[0070] S401, turn on laser 1 and chopper 2, adjust the position of the laser beam emitted from laser 1 so that the laser beam spot illuminates the center of the first reflector 3 and the second reflector 4;

[0071] S402, the emitted laser is reflected by the first reflecting mirror 3 and the second reflecting mirror 4 to the center of the back focal plane of the first objective lens 5, which can be adjusted in three dimensions;

[0072] S403, finely adjust the first objective lens 5 so that the emitted laser spot converged by the first objective lens 5 illuminates the center of the first fiber collimator 7, which can be adjusted in three dimensions.

[0073] S404, finely adjust the position of the first fiber collimator 7 to maximize the coupling power between the converging laser and the single-mode fiber 11.

[0074] S5, turn on the light source of the scanning noise infrared near-field optical microscope, use its optical CCD29 imaging system to observe the relative position of the sample to be tested and the laser spot, and use the four-dimensional adjustment stage of the laser-introduced probe system module to adjust the detection position of the laser spot illuminating the sample to be tested.

[0075] The specific steps for adjusting the laser spot onto the detection position of the sample using the four-dimensional adjustment stage of the laser-introduced probe system module are as follows:

[0076] S501, the laser focused onto the first fiber collimator 7 is introduced into the laser introduction probe system module through the single-mode fiber 11 of the corresponding wavelength.

[0077] S502, adjust the converging lens 13 to focus the laser beam to the center of the back focal plane of the second objective lens 18;

[0078] S503, adjust the three-dimensional displacement stage 16 and the rotational displacement stage 17 of the four-dimensional adjustment stage to introduce the focusing laser onto the sample to be tested.

[0079] S6, laser-excited probe scanning imaging;

[0080] Using a scanning noise near-field optical microscope module, the thermal distribution of the sample under test is scanned and imaged under laser excitation;

[0081] The sample to be tested in this embodiment is as follows: Figure 3 As shown, the metal structure consists of a 50nm thick gold (Au) substrate and a 5mm thick silicon (Si) substrate.

[0082] The test diagram of this embodiment is as follows: Figure 4 As shown, a laser modulated by chopper 2 is incident on a metal nanostructure located on a silicon substrate. Electrons in the metal nanostructure are excited by the laser and generate disturbances, radiating infrared evanescent waves on the surface of the sample to be tested. The nanoscale probe 21 scatters the infrared evanescent waves radiated from the surface of the sample to be tested. The scattered infrared light is collected by a long-wave infrared microscope objective 22 and focused onto an ultra-sensitive infrared detector. An external circuit converts the optical signal into an electrical signal for digital processing and final imaging.

[0083] like Figure 3 The sample to be tested is scanned along the X-axis in the direction of the middle arrow, and the acquired AFM, far-field, and near-field information is as follows: Figure 5 , Figure 6 As shown, Figure 5 This study demonstrates a comparison between far-field one-dimensional scanning and AFM scanning of metal structures. Due to the diffraction limit in long-wave infrared (resolution ~20 μm), far-field scanning of samples cannot clearly reveal the detailed information of the metal structure. In contrast, AFM, based on atomic force detection, possesses high resolution and can clearly detect the sharp edges of the metal structure. Figure 6The comparison between one-dimensional scanning and near-field scanning of the AFM of the metal structure was demonstrated. The constructed optically excited scanning noise near-field optical microscope also has high resolution and can clearly show the sharp edges of the metal structure. This verifies that the system has the ability to break through the diffraction limit in the long-wave infrared band.

[0084] Figure 7 The test results of the near-field signal of the sample under test with the probe height are shown. The signal of the sample under test decreases rapidly with the increase of probe height and then flattens out after 150 nm. This exponential decay trend verifies that the measured signal is a near-field signal. Figure 8 The near-field imaging results of the constructed laser-excited scanning noise infrared near-field optical microscope are shown, with the imaging area corresponding to... Figure 3 The area marked by the dashed box in the image clearly shows the sharp edges of the metal structure. Since the near-field signal intensity is proportional to the thermal signal intensity generated by laser excitation, it is possible to visually compare that the temperature on Au under laser excitation is higher than that on the Si substrate.

[0085] S7, disconnect the instrument, turn off the light source, remove the sample, and the measurement is complete.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. All equivalent changes and modifications made within the scope of the claims of this invention should be considered within the technical scope of this invention.

Claims

1. A nanoscale infrared photothermal imaging system, characterized in that: It includes a scanning noise infrared near-field optical microscope and a laser excitation device; wherein, the laser excitation device includes a free space light coupling to fiber optic module and a laser introduction probe system module; The free space light coupled to the fiber optic module includes a laser (1) with adjustable power, a chopper (2), a mirror group with adjustable angle, a first objective lens (5) with three-dimensional adjustment, and a first fiber collimator (7) with three-dimensional adjustment, all mounted on the same optical breadboard (10), as well as a single-mode fiber (11) adapted to the laser wavelength. The first objective lens (5) is used to finely adjust its position to focus the laser onto the end face of the single-mode fiber (11); the first fiber collimator (7) is used to finely adjust the position of the single-mode fiber (11) to couple the focused laser into the single-mode fiber (11); The reflector group consists of a first reflector (3) and a second reflector (4). After the laser modulated by the chopper (2) enters the first reflector (3), it is reflected into the second reflector (4). The second reflector (4) reflects the laser into the center of the back focal plane of the first objective lens (5). The first reflector (3) and the second reflector (4) adjust their angles according to the wavelength of the laser. The laser-introduced probe system module includes a four-dimensional adjustment stage, a second objective lens (18), a second fiber collimator (12), and a converging lens (13); the four-dimensional adjustment stage consists of a three-dimensional displacement stage (16) and a rotary displacement stage (17); the rotary displacement stage (17) is set on the three-dimensional displacement stage (16); The second fiber collimator (12) is connected to the first fiber collimator (7) via a single-mode fiber (11); the converging lens (13) converges the laser onto the back focal plane of the second objective (18); the second objective (18) converges the laser onto the probe (21) of the scanning noise infrared near-field optical microscope; after fine adjustment by the four-dimensional adjustment stage, the converged laser spot is moved to the tip of the probe (21); The four-dimensional adjustment stage and the scanning noise infrared near-field optical microscope are set on the same optical platform (30).

2. The nanoscale infrared photothermal imaging system according to claim 1, characterized in that: The free-space light coupling to the fiber optic module also includes a three-dimensional fine displacement stage (6), a two-dimensional fine displacement stage (8), and a Z-axis fine displacement stage (9); the first objective lens (5) is set on the three-dimensional fine displacement stage (6), the first fiber collimator (7) is set on the two-dimensional fine displacement stage (8), and the two-dimensional fine displacement stage (8) is set on the Z-axis fine displacement stage (9).

3. The nanoscale infrared photothermal imaging system according to claim 2, characterized in that: The laser-introduced probe system module also includes a cage-type support and an optical support rod (15), wherein the cage-type support is composed of a cage-type support rod (14); The second fiber collimator (12), the converging lens (13), and the second objective lens (18) are sequentially arranged in a cage-like support. The cage-like support is arranged on a rotating stage (17), and the rotating stage (17) is arranged on a three-dimensional stage (16) via an optical support rod (15). The three-dimensional stage (16) and the rotating stage (17) are adjusted to converge the laser onto the probe (21) of the scanning noise infrared near-field optical microscope.

4. The nanoscale infrared photothermal imaging system according to claim 3, characterized in that: The cage support consists of four cage supports (14).

5. The imaging method of the nanoscale infrared photothermal imaging system according to any one of claims 1-4, characterized in that: The specific steps are as follows: S1, the sample to be tested is mounted on the three-dimensional fine stage (20) of the scanning noise infrared near-field optical microscope; S2, a low-temperature environment was established by scanning a noise infrared near-field optical microscope using a low-temperature Dewar (23); S3, connect the electrical test channel of the scanning noise infrared near-field optical microscope and read the electrical characteristics of the detector in the low temperature Dewar (23); if the electrical characteristics of the detector in the low temperature Dewar (23) are normal, proceed to step S4; if the electrical characteristics of the detector in the low temperature Dewar (23) are abnormal, jump to step S2, restore the low temperature Dewar (23) to room temperature naturally, and then cool it again. S4, laser introduction; Turn on the laser (1) and chopper (2), and convert the output laser into a fiber laser by coupling free space light to the fiber module. Connect the fiber laser to the laser introduction probe system module so that the fiber laser is focused onto the probe (21) of the scanning noise infrared near-field optical microscope. Make fine adjustments to the four-dimensional adjustment stage to move the focused laser spot to the tip of the probe (21). S5, turn on the light source of the scanning noise infrared near-field optical microscope, use its optical CCD imaging system to observe the relative position of the sample to be tested and the laser spot, and use the four-dimensional adjustment stage of the laser-introduced probe system module to adjust the detection position of the laser spot illuminating the sample to be tested. S6, laser-excited probe scanning imaging; Using a scanning noise near-field optical microscope module, the thermal distribution of the sample under test is scanned and imaged under laser excitation; S7, disconnect the instrument, turn off the light source, remove the sample, and the measurement is complete.

6. The imaging method according to claim 5, characterized in that: The specific steps of S4 are as follows: S401, turn on the laser (1) and chopper (2), adjust the position of the laser (1) output light so that the laser spot illuminates the center of the first reflector (3) and the second reflector (4); S402, using the first mirror (3) and the second mirror (4) to reflect the emitted laser to the center of the back focal plane of the first objective lens (5) that can be adjusted in three dimensions; S403, finely adjust the first objective lens (5) so that the emitted laser spot converged by the first objective lens (5) illuminates the center of the first fiber collimator (7) that can be adjusted in three dimensions; S404, finely adjust the position of the first fiber collimator (7) to maximize the coupling power between the converging laser and the single-mode fiber (11).

7. The imaging method according to claim 5, characterized in that: The specific steps in S5 for adjusting the position of the laser spot on the sample using the four-dimensional adjustment stage of the laser-introduced probe system module are as follows: S501, the laser focused to the first fiber collimator (7) is introduced into the laser introduction probe system module through a single-mode fiber (11) of the corresponding wavelength; S502, adjust the converging lens (13) to converge the laser to the center of the back focal plane of the second objective lens (18); S503, adjust the three-dimensional displacement stage (16) and the rotational displacement stage (17) of the four-dimensional adjustment stage to introduce the focusing laser onto the probe (21) of the scanning noise infrared near-field optical microscope.

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