A Terahertz Near-Field Microscope System Based on a Raman Spectrometer and Its Usage Method

Abstract

The present invention discloses a terahertz near-field microscope system based on a Raman spectrometer and a usage method, a terahertz near-field microscope and a Raman spectrometer. The terahertz near-field microscope is used to process the terahertz near-field signal scattered by a sample to be measured, and obtain the terahertz near-field spectral image of the sample to be measured based on the terahertz near-field signal; the Raman spectrometer is used to generate a laser to process the sample to be measured to generate Raman scattered light, and the Raman scattered light is processed through an optical path to collect the corresponding spectral signal, and the spectral signal is transmitted to a processor for processing. After the Raman spectrometer is combined with the terahertz near-field microscope in the present invention, the frequency spectrum range is broadened, so that the ultraviolet band, the visible light band and the terahertz band are used together in the system, which not only has the characteristics of fast and accurate Raman imaging, but also has the advantages of high penetration and super-resolution imaging of the terahertz near-field technology.

Description

Technical Field

[0001] The present invention relates to the field of bioanalysis, and particularly, to a terahertz near-field microscope system based on a Raman spectrometer and a method of using the same. Background Art

[0002] Raman spectroscopy belongs to molecular spectroscopy. Raman spectroscopy technology is an analytical method that analyzes the scattered spectrum with a frequency different from that of the incident light to obtain information on molecular vibration and rotation, and is applied to the study of molecular structure. Raman imaging technology can provide chemical composition, structure, and spatial information of molecules, and has great application prospects in the biomedical field. Cells, tissues, and organs in different states have different biochemical compositions and spectral characteristics. By analyzing Raman spectral images, the pathological conditions of the sample to be measured can be provided, and normal and diseased tissues can be effectively distinguished. Since different substances have different characteristic spectra, qualitative analysis of biological cells can be performed through Raman spectroscopy. Therefore, observing information such as the composition and structure of substances using Raman spectroscopy technology has the most important application value in the biomedical field.

[0003] A Raman spectrometer generally consists of five parts: a light source, an external optical path, a dispersion system, and an information processing and display system. First, it must have an excitation wavelength. Generally, the excitation wavelengths used are several fixed ones, such as 780 nm, 532 nm, 1064 nm, etc. Second, it must have a receiver. Since the signals of Raman scattering are non-directional, sampling accessories such as an integrating sphere and a collimating lens are used.

[0004] The Raman spectrometer uses ultraviolet and visible light bands to irradiate the sample to obtain the scattered spectrum. The Raman spectrometer uses the above-mentioned band of laser to excite the sample to be measured, generating Raman shift signals. The Raman shift only depends on the structure of the scattering molecule. The Raman scattering signals are obtained through an efficient optical signal acquisition and processing system, and the composition of the sample to be measured is analyzed quickly and accurately. Therefore, Raman spectroscopy can be used as the fingerprint spectrum of molecular vibration energy levels. It can perform point, line, and surface scanning tests on solid (powder, crystal, amorphous, or thin film) and liquid samples. However, the Raman spectrometer has a narrow spectral range, poor penetration, and low imaging resolution, which limits its application. Summary of the Invention

[0005] The object of the present invention is to solve the problems of the narrow spectral range, poor penetration, and low imaging resolution of the Raman spectrometer.

[0006] To achieve the above object, the present invention provides a terahertz near-field microscope system based on a Raman spectrometer. The system includes a terahertz near-field microscope and a Raman spectrometer, wherein:

[0007] The terahertz near-field microscope includes a terahertz unit and an atomic force microscope unit. The atomic force microscope unit is used to emit a laser to the tip cantilever of the atomic force probe, and the laser is reflected back to the quadrant detector after being reflected by the tip cantilever. The terahertz unit is used to focus the terahertz wave on the area between the tip of the atomic force probe and the sample to be measured, generate a scattered terahertz near-field signal, and obtain the terahertz near-field spectral image of the sample to be measured based on the terahertz near-field signal;

[0008] The Raman spectrometer is used to generate a laser. After being processed by the optical path, the laser irradiates the sample to be measured to generate Raman scattered light. After being processed by the optical path, the Raman scattered light collects the corresponding spectral signal and transmits the spectral signal to the processor for processing.

[0009] A Raman spectrometer can only observe the spectral characteristics of substances by forming a Raman spectrum through the frequency change of scattered light, and there is interference from the fluorescence phenomenon in Fourier transform Raman spectroscopy analysis; during Fourier transform spectroscopy analysis, the problem of non-linearity of curves often occurs; during the testing process, the introduction of any substance will cause a certain degree of contamination to the measured body system, which is equivalent to introducing the possibility of some errors and will have a certain impact on the analysis results. At the same time, since water is a polar substance, water has a strong absorption effect on terahertz waves, while the Raman scattering of water is very weak, and Raman spectroscopy is an ideal tool for studying biological samples and chemical compounds in aqueous solutions. Most importantly, an atomic force microscope can also measure the interaction forces between active molecules on the cell membrane surface and is an effective means of observing the internal structure of cells. In view of this, through research, this application proposes a solution based on the combination of Raman spectroscopy technology and terahertz near-field microscopy, which perfectly combines terahertz near-field technology and laser Raman spectroscopy technology and has the characteristics of high-speed and extremely high-resolution imaging. It not only has the characteristics of strong Raman spectral peak characteristics, fewer overlapping spectral bands, and being able to perform differential analysis and quantitative analysis; it can also explore the molecular structure of biological macromolecules through the very rich physical and chemical information contained in terahertz spectra (transmission spectra and reflection spectra). Whether it is a Raman spectrum or a terahertz time-domain spectroscopy system, both can be used as fingerprint spectra to qualitatively identify substances. The wavelength range of the Raman spectrum is 2.5μm - 250μm, while the wavelength range of the terahertz spectrum is 30μm - 3000μm. Terahertz time-domain spectroscopy can test fingerprint spectrum information in a higher frequency band, and there is partial overlap between the two. After combining the two, the resonance response of the substance at this frequency can play a role of mutual verification. Moreover, the range of the fingerprint spectrum is also greatly broadened. Therefore, combining the two can not only accurately obtain the spectral characteristics of biological samples through Raman spectroscopy for qualitative and quantitative analysis, but also achieve many advantages such as the high penetrability of terahertz and the high resolution of atomic force microscopy. At the same time, the combination of Raman spectroscopy technology and terahertz near-field microscopy can, to a certain extent, make up for the shortcoming that terahertz waves attenuate quickly in water. The purpose of double identification of substances by spectrum and imaging is achieved. Therefore, this system can play a key role in biomedical research.

[0010] The terahertz near-field microscope is a new type of super-resolution microscope that combines the atomic force microscope and terahertz technology. It not only has the high penetration of terahertz waves but also the super-resolution ability of the atomic force microscope. The vibration and rotation energy levels of many biological macromolecules are just in the terahertz band. Since terahertz waves have the fingerprint characteristics of reflecting the structure and properties of substances, and the photon energy is low, far less than the energy of X-rays, they will not cause harmful ionization to biological macromolecules, biological cells, and tissues, and are particularly suitable for in vivo examination of biological tissues. Therefore, compared with existing medical imaging technologies, terahertz wave spectral imaging technology has more unique and applicable physical characteristics. Therefore, the advantages of the terahertz near-field microscope in biological imaging are unique.

[0011] Further, the terahertz unit includes: a femtosecond laser light source, an optical fiber beam splitter, an optical fiber delay line, several plane mirrors, a transmitting antenna, two focusing mirrors, and a receiving antenna; the femtosecond laser light source is used to generate a laser, which is divided into a first transmitted light and a first received light by the optical fiber beam splitter. The first transmitted light is delayed by the optical fiber delay line and then focused and incident on the transmitting antenna to generate terahertz waves. The terahertz waves are focused by one of the focusing mirrors to the region between the atomic force probe tip and the sample, generating a scattered terahertz near-field signal. The terahertz near-field signal is focused by the other focusing mirror and then incident on the receiving antenna. The terahertz near-field signal and the first received light act on the receiving antenna to make the carriers move directionally and then generate a first electrical signal. The electrical signal is transmitted to the processor and obtained the terahertz near-field signal of the sample to be measured after phase-locked demodulation processing. Based on this terahertz near-field signal, terahertz near-field spectral imaging is performed in the atomic force microscope unit.

[0012] Further, the atomic force microscope unit includes: an atomic force probe, a quadrant laser emitter, a quadrant detector, and a sample stage; the quadrant laser emitter is used to emit a laser to the tip cantilever of the atomic force probe. The laser is reflected back to the quadrant detector by the tip cantilever. The sample stage is a hollow stage, and the sample is suspended in the hollow area of the sample stage. The sample is fixed at the center of the stage by a clip to ensure that the laser passing through the objective lens can be focused on the sample.

[0013] Further, the Raman spectrometer includes:

[0014] a light source, a first band-pass filter, a mirror, a heat dissipation light collection system, a second band-pass filter, a notch filter, several plane mirrors, an edge filter, a focusing lens, a spectrometer adjustable slit, a collimating mirror, a reflection focusing mirror, a grating, a cylindrical mirror, a CCD detector, and a processor;

[0015] Among them, the laser emitted by the light source is filtered by the first band-pass filter and then reflected by the reflector to the sample to be measured. The laser irradiates the sample to be measured to generate Raman scattered light. The Raman scattered light is collected by the heat dissipation light collection system and then enters the second band-pass filter. After being filtered by the second band-pass filter, it enters the notch filter. After being filtered by the notch filter, it enters the focusing lens. The focusing lens converges the signal to the adjustable slit of the spectrometer. The signal exits from the adjustable slit of the spectrometer and then enters the collimating mirror. The signal is collimated by the collimating mirror and then refracted to the reflecting surface of the reflecting focusing mirror. The signal is reflected by the reflecting surface of the reflecting focusing mirror to the grating. The grating disperses the Raman scattered light carrying the signal of the sample to be measured. The dispersed signal enters the focusing surface of the reflecting focusing mirror to converge the signal and then to the cylindrical mirror for astigmatism correction. The corrected signal is received by the CCD detector for its spectral information, and the spectral information is transmitted to the processor for processing.

[0016] Further, the reflecting focusing mirror includes 5 surfaces, namely the top surface, the bottom surface, 2 side surfaces and the back surface. Among them, the top surface and the bottom surface are parallel to each other, and one of the 2 side surfaces is a reflector and the other is a parabolic focusing mirror.

[0017] Among them, the reflecting focusing mirror is a specially designed mirror in the present invention, which achieves the purpose of saving space and improving efficiency. Originally, a plane mirror was needed to refract the light onto the grating for dispersion and then another plane mirror was placed for refraction, and finally a parabolic mirror was placed for focusing. In this way, there are more adjustable mirror surfaces, the steps are cumbersome, and there are more variable factors. Therefore, a reflecting focusing mirror is designed (its 2 side surfaces are waist surfaces, one waist is a plane mirror and the other waist is a parabolic focusing mirror).

[0018] Further, the first band-pass filter is used to filter the direct light in the laser, and the second band-pass filter, the notch filter and the edge filter are all used to filter the scattered light in the Raman scattered light.

[0019] Further, the adjustable slit of the spectrometer is used for spatial filtering, the width of the adjustable slit of the spectrometer can be adjusted and the width of the adjustable slit of the spectrometer can be adjusted in the horizontal direction or the vertical direction.

[0020] Preferably, the filters in the second band-pass filter, the edge filter and the notch filter are all narrow-band filters.

[0021] Preferably, the center wavelength of the narrow-band filter is 785 ± 3 nm, the bandwidth is 10 nm, and the cut-off range is 200 - 1200 nm.

[0022] In order to achieve the above-mentioned invention purpose, the present invention also provides a use method of the above-mentioned terahertz near-field microscope system based on a Raman spectrometer, and the method includes:

[0023] Step 1: Debug the system and turn on the system power after debugging is completed;

[0024] Step 2: Fix the sample to be measured on the sample stage through the clamping piece;

[0025] Step 3: Turn on the four-quadrant laser emitter, adjust the angle of the four-quadrant laser emitter so that the four-quadrant detector can receive the reflected signal, bring the atomic force probe close to the sample to be measured, turn on the femtosecond laser light source, and feed the scattered terahertz near-field signal to the lock-in amplifier through the receiving antenna via the voltage amplifier, and transmit the amplified signal to the processor for near-field imaging;

[0026] Step 4: Turn on the light source in the Raman spectrometer. The laser emitted by the light source is processed and then irradiated onto the sample to be measured to generate Raman scattered light. The signal after processing the Raman scattered light is received by the CCD detector for its spectral information, and after the spectral information is received, it is transmitted to the processor for processing to display the spectral result.

[0027] One or more technical solutions provided by the present invention have at least the following technical effects or advantages:

[0028] After the present invention combines the Raman spectrometer with the terahertz near-field microscope, the spectral range is broadened, so that the ultraviolet band, visible light band, and terahertz band are used together in the Raman-terahertz near-field system. It not only has the characteristics of fast and accurate Raman imaging, but also has the advantages of high penetration and super-resolution imaging of terahertz near-field technology. Description of the Drawings

[0029] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the present invention, but do not limit the embodiments of the present invention;

[0030] Figure 1 is a schematic diagram of the composition of a terahertz near-field microscope system based on a Raman spectrometer;

[0031] Figure 2 is a schematic diagram of the processing flow of a terahertz near-field microscope system based on a Raman spectrometer;

[0032] Figure 3 is a schematic diagram of the composition of the optical system of the Raman spectrometer;

[0033] Figure 4 is a schematic diagram of the composition of the dispersion system of the Raman scattering system;

[0034] Among them, a 780 nm femtosecond laser light source - 1, an optical fiber beam splitter - 2, a plane mirror - 3, a fast delay line - 4, a transmitting antenna - 5, a quadrant receiver - 6, a quadrant laser emitter - 7, an atomic force probe - 8, a focusing mirror - 9, a sample stage - 10, a receiving antenna - 11, a 785 nm laser light source - 15, a first band - pass filter - 16, a mirror - 17, a scattered light collection system - 12, a second band - pass filter - 13, a notch filter - 14, an edge filter - 18, a focusing lens - 19, a spectrometer adjustable slit - 20, a collimating mirror - 21, a reflecting focusing mirror - 22, a grating - 23, a cylindrical mirror - 24, a CCD detector - 25 and a control computer - 26. Detailed implementation manners

[0035] In order to more clearly understand the above - mentioned objects, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0036] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described within the scope hereof. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0037] Embodiment 1

[0038] Please refer to Figure 1 , Embodiment 1 of the present invention provides a terahertz near - field microscope system based on a Raman spectrometer, including a terahertz near - field microscope in the first part, specifically including: a 780 nm femtosecond laser light source 1, an optical fiber beam splitter 2, several plane mirrors 3, a fast delay line 4, a transmitting antenna 5, a quadrant receiver 6, a quadrant laser emitter 7, an atomic force probe 8, a focusing mirror 9, a sample stage 10 and a receiving antenna 11, and a Raman spectroscopy system in the second part, specifically including: a 785 nm laser light source 15, a first band - pass filter 16, a mirror 17, a scattered light collection system 12, a second band - pass filter 13, a notch filter 14, an edge filter 18, a focusing lens 19, a spectrometer adjustable slit 20, a collimating mirror 21, a reflecting focusing mirror 22, a grating 23, a cylindrical mirror 24, a CCD detector 25 and a control computer 26.

[0039] In the first part, the 780 nm femtosecond laser source 1 is split into transmitted light and received light after passing through the fiber optic beam splitter 2. The transmitted light passes through the fast delay line 4 and then is incident on the transmitting antenna 5. After passing through a plane mirror 3 and a focusing lens 9, it is focused on the atomic force probe 8. The four-quadrant laser emitter 7 emits laser light that is reflected after being incident on the probe cantilever and is received by the four-quadrant receiver 6. The terahertz near-field scattering signal enters the receiving antenna 11 after being scattered by the tip, and the test sample is placed on the sample stage 10.

[0040] Among them, the atomic force probe measures the three-dimensional topography by the real-time distance feedback between the tip and the sample. After the laser light emitted by the four-quadrant laser emitter 7 irradiates the tip cantilever, it is reflected back into the four-quadrant receiver 6. In this way, the tip jitter will cause the laser light reflected into the four-quadrant receiver 6 to hit different positions on the four-quadrant receiver 6. By recording this different position, the distance between the tip and the sample can be recorded in real time, thus realizing three-dimensional measurement.

[0041] The transmitted light generates terahertz after passing through the transmitting antenna and then reaches the receiving antenna after being scattered by the tip. When the received light irradiates the receiving antenna, free carriers are generated inside the receiving antenna, and at this time, their movement directions are disordered. At this time, the scattered terahertz reaches the receiving antenna, and the electric field of the terahertz causes the carriers inside the antenna to move in a directional manner, thus generating a regular electrical signal, so as to achieve the purpose of detecting the scattered terahertz wave. The scattered terahertz wave itself is generated by the interaction between the sample and the tip, so the purpose of detecting the sample is also achieved. The purpose of the detection light is to generate free carriers inside the detection antenna, and the scattered terahertz is to make these free carriers move in a directional manner, which is convenient for reading the electrical signal, and the read electrical signal is used as the imaging signal.

[0042] The second part is divided into an optical path system and a dispersion system. In the optical path system, the 785 nm laser source 15 emits light and is focused on the sample to be measured after passing through the first band-pass filter 16 and the mirror 17. After being scattered by the sample to be measured, the Raman scattered light passes through the scattered light collection system 12, the second band-pass filter 13 and the notch filter 14 in sequence, and then reaches the edge filter 18 after reflection, and then the signal is converged by the focusing lens 19 and reaches the adjustable slit 20 of the spectrometer. After being collimated by the collimating mirror 21, it is refracted and reaches the reflection focusing mirror 22. The grating 23 disperses the Raman scattered light with the sample signal, and after the signal is converged by the other side of the reflection focusing mirror 22, the astigmatism is corrected by the cylindrical mirror 24, and finally the spectral information is received by the CCD detector 25 and then transmitted to the control computer 26 for processing.

[0043] A laser light source emits a monochromatic laser beam, which irradiates the sample to be measured. The laser interacts with the sample to generate Raman scattered light. The Raman scattered light is emitted from the surface of the sample, usually at a very small angle. The scattered light collection system needs to capture this scattered light. To achieve this goal, an optical element such as a mirror or a lens is usually used. The lens can focus the scattered light, thereby improving the light collection efficiency of the system.

[0044] By combining a Raman spectroscopy system with a terahertz near-field imaging system above the sample stage, the invention not only has the characteristics of high speed and extremely high resolution of Raman spectroscopy technology, but also can accurately obtain the spectral characteristics of biological samples through Raman spectroscopy for qualitative and quantitative analysis. At the same time, it can also achieve many advantages such as high penetrability of terahertz and high resolution of atomic force microscopy. The purpose of double identification of substances by spectrum and imaging is realized, thus making the identification and analysis of substances more accurate.

[0045] Among them, the present invention combines a Raman spectrometer with a terahertz near-field microscope. The existing systems do not use near-field and Raman in combination to detect samples, which will have great limitations, such as a narrow detection range and incomplete signal collection of a single system. In sample detection, the sample will have information representation in the terahertz near-field, and also has information representation in the Raman spectrometer. After being used in combination, it can realize the simultaneous detection of the chemical composition and morphology at the nanoscale on the surface of the material. (Near-field; morphology, spectrometer: composition), and substances can be double-identified. For example, the near-field characteristics of some different materials will have a certain degree of similarity, and it may not be possible to judge solely by the near-field. After adding a Raman spectrometer for the identification of the composition, substances can be identified more efficiently. The present invention is not a simple combination. Among them, the first band-pass filter 16, the second band-pass filter 13, the notch filter 14, and the edge filter 18 are all optical filters designed for the Raman spectroscopy system, which are used to eliminate the direct light, scattered light or other interference light of the laser source, thereby improving the signal-to-noise ratio of the Raman signal.

[0046] Among them, both the first and second band-pass filters are selected as narrow-band filters. The narrow-band filter has higher spectral selectivity and signal-to-noise ratio, as well as the characteristics of high transmittance and high optical density. The center wavelength is designed to be 785 ± 3 nm, the bandwidth is 10 nm, the transmittance can reach more than 80%, and the cut-off range is 200 - 1200 nm. The notch filter and the edge filter are designed in the same way.

[0047] In a Raman spectrometer, the selection and use of filters are crucial for achieving high-resolution and high-sensitivity Raman spectroscopy measurements. Multiple filters make the resolution accuracy of the extracted signal higher.

[0048] In the Raman system of the present invention, a spectrometer adjustable slit 20 is designed. The slit can limit the incidence of light in the optical path, playing a role of spatial filtering and helping to improve the spatial resolution of the Raman spectrometer. By reducing the influence of scattered light, the slit helps to reduce the interference of background light and improve the signal-to-noise ratio. Therefore, a slit system that can adjust the slit distance and rotation is designed. The width of the spectrometer adjustable slit 20 can be adjusted, and the overall direction of the spectrometer adjustable slit 20 can be rotated. For example, if there is a spectrometer adjustable slit 20 on a panel, the width of the spectrometer adjustable slit 20 in the horizontal or vertical direction can be adjusted by adjustment. By rotating the panel and then adjusting, the width of the spectrometer adjustable slit 20 in the vertical or horizontal direction can be adjusted. It can be adjusted vertically or horizontally after rotation, and the incident light angle can be controlled so that when the light enters the grating or other optical elements, it has a small angular distribution, which is beneficial to improving the performance of the spectrometer.

[0049] Spectral resolution: The width of the slit directly affects the resolution of the spectrometer. Generally, the narrower the slit, the higher the spectral resolution, but at the same time, it will cause a decrease in signal intensity. Therefore, when designing the optical path, it is necessary to balance between spectral resolution and signal intensity to meet the experimental requirements.

[0050] In the technical solution of the present invention, compared with the traditional technology, the addition of the spectrometer adjustable slit 20 is more beneficial to the testing of samples. The added reflection focusing mirror 22 is more convenient and efficient and saves space.

[0051] In the present invention, the specific process of the system can be as Figure 2As shown in the figure, first, the laser of the near-field system is generated by a 780 nm high-energy fiber femtosecond laser. The laser pulse width is 83 fs, the repetition frequency is 80 MHz, and the optical path difference Δz between two adjacent laser pulses is 3.75 m. The power is 140 mW, and it is connected to the transmitting and receiving antennas according to a beam splitting ratio of 1:1, which is used to generate and receive terahertz waves. The transmitting antenna is a butterfly antenna composed of low-temperature grown gallium arsenide or gallium arsenide. The thin film covered with metal contacts can be used as an optical excitation broadband, which has a small bandwidth, a large signal amplitude, and is recommended as a detector. The antenna length l = 44 μm, and the gap distance is 6 μm. The receiving antenna also uses the above butterfly antenna, with a length l = 44 μm and a gap distance of 6 μm. When the terahertz light spot is scattered after being focused on the sample surface by the focusing mirror, it is collected by the focusing test system. The focal length of the focusing mirror is 16 mm. The collected signal is amplified by a current amplifier and then connected to the input end of the lock-in amplifier. The current amplification factor is 20 MV / A. After the piezoelectric ceramic is applied with a voltage, the jitter frequency of the probe is Ω. Under the action of the focused terahertz light spot at the tip, the scattered near-field evanescent wave (near-field signal) is amplified. After being received by the receiving antenna, it is first connected to a current amplifier and then to a lock-in amplifier for signal demodulation to generate a 123-order signal. The demodulation frequency is connected to the lock-in amplifier. The lock-in amplifier inputs the third-order demodulated signal into the computer, and frequency demodulation imaging is performed on the signals of these 3 channels respectively. The higher the order, the weaker the signal, but the stronger its ability to reflect the essential information of the near field.

[0052] The Raman spectroscopy system consists of five parts: a light source, an external optical path, a dispersion system, a receiving system, and an information processing system. Among them, the laser provides a stable excitation light source with good monochromaticity and high power. After the laser is incident on the sample, Raman scattering occurs, and the generated Raman scattering will be collected by the external optical path. A grating is set in the dispersion system to separate the Raman scattered light according to the wavelength space. Finally, the spectral signal received is analyzed and processed by the CCD detector system.

[0053] The optical structure of the spectrometer is divided into an external optical path system and a dispersion system. The optical system structure of the Raman spectrometer is as Figure 3 shown. The laser beam emitted by the 785 nm laser passes through the first band-pass filter and then is refracted by a plane mirror to irradiate the sample. After scattering, the scattered light is collected by the scattered light collection system 12. Next, the Raman scattered light passes through the second band-pass filter 13 and the notch filter 14 in turn, and then reaches the edge filter 18 after reflection. Then, the signal is converged by the focusing lens 19 and reaches the adjustable slit 20 of the spectrometer.

[0054] The dispersion system of the Raman scattering system is as Figure 4As shown in the figure, after the scattered light reaches the reflection focusing mirror, a reflecting mirror with one flat side reflects the signal to a grating to disperse the Raman scattered light, and then a focusing mirror with one paraboloid side converges the divided light beams. Finally, the astigmatism is corrected by a focusing lens, and the spectral information is received by a CCD detector.

[0055] Example Two

[0056] Based on Example One, the present invention also provides a method for using a terahertz near-field microscope system based on a Raman spectrometer. The method includes:

[0057] Debugging: Check whether the optical path is offset and whether the connecting wires are accurate. After preparation is completed, the power supply can be turned on. Sample installation: The sample is fixed at the center of the stage by a clip to ensure that the laser passing through the objective lens can be focused on the sample.

[0058] Next, adjust the near-field microscope system. Turn on the quadrant laser emitter and adjust the angle to ensure that the quadrant detector can receive the feedback. Then adjust the frequency setting on the software system. After completion, the needle can be lowered. Finally, turn on the 780nm laser, and the scattered terahertz signal is fed back to the lock-in amplifier through the receiving antenna, and the amplified signal is transmitted to the computer for near-field imaging.

[0059] Next, turn on the 785nm laser in the Raman spectroscopy optical path. The scattered Raman spectrum will be collected by the collection system, then incident on the CCD through other optical mirrors, and finally the spectral results are displayed by the software.

[0060] Through Raman spectroscopy analysis, we can obtain information on the molecular vibration, rotation, and other low-frequency modes of substances, thereby revealing the chemical structure, crystal structure, material stress, and other characteristics of the sample. Raman spectrometers can be applied in multiple fields, such as materials science, biomedicine, chemistry, environmental science, etc.

[0061] The signal measured by the Raman spectrometer is presented in the form of a spectrogram. The spectrogram usually includes two axes: the horizontal axis represents the Raman shift (expressed in wavenumbers, unit: cm -1 ) and the vertical axis represents the light intensity. The Raman shift is the energy difference between the laser excitation light and the Raman scattered light and is related to the vibration and rotation modes of molecules in the substance. The light intensity reflects the intensity of the scattered light and is related to the concentration of specific components in the sample.

[0062] From the Raman spectrum, we can observe different Raman peaks, and each peak corresponds to a specific vibration or rotation mode in the substance. By analyzing the position, intensity, and shape of these Raman peaks, the chemical composition, structural information, and other properties of the sample can be obtained. For example, by analyzing the position of the Raman peaks, specific chemical bonds or functional groups in the sample can be identified; by comparing the intensities of the Raman peaks, the relative concentrations of different components in the sample can be estimated.

[0063] The signals measured by the terahertz near-field microscope are presented in the form of spectrograms or images. For spectral analysis, the horizontal axis represents the terahertz frequency or wave number, and the vertical axis represents parameters such as light intensity or absorption coefficient. For imaging analysis, the results are usually presented in the form of two-dimensional images or three-dimensional surface plots, where each pixel corresponds to a specific near-field signal intensity, reflecting the properties of the material.

[0064] Finally, the relevant data is exported for calculation or plotting.

[0065] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0066] Obviously, those skilled in the art can make various changes and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A terahertz near-field microscope system based on a Raman spectrometer, characterized in that, The system includes a terahertz near-field microscope and a Raman spectrometer, where: The terahertz near-field microscope includes a terahertz unit and an atomic force microscope unit. The atomic force microscope unit is used to emit a laser to the tip cantilever of the atomic force probe, and the laser is reflected back to the quadrant detector after passing through the tip cantilever. The terahertz unit is used to focus the terahertz wave onto the area between the tip of the atomic force probe and the sample to be measured, generate a scattered terahertz near-field signal, and obtain a terahertz near-field spectral image of the sample to be measured based on the terahertz near-field signal; The Raman spectrometer is used to generate a laser, and the laser is irradiated on the sample to be measured after passing through optical path processing to generate Raman scattered light. The Raman scattered light is collected with a corresponding displacement spectral signal after passing through optical path processing, and the displacement spectral signal is transmitted to a processor for processing. The terahertz unit includes: a femtosecond laser light source, an optical fiber beam splitter, an optical fiber delay line, several plane mirrors, a transmitting antenna, two focusing mirrors, and a receiving antenna. The femtosecond laser light source is used to generate a laser that is divided into a first transmitted light and a first received light by the optical fiber beam splitter. The first transmitted light is delayed by the optical fiber delay line and then focused and incident on the transmitting antenna to generate a terahertz wave. The terahertz wave is focused by one of the focusing mirrors onto the area between the tip of the atomic force probe and the sample, generating a scattered terahertz near-field signal. The terahertz near-field signal is focused by the other focusing mirror and then incident on the receiving antenna. The terahertz near-field signal and the first received light act on the receiving antenna to cause the carriers to move directionally and generate a first electrical signal. The first electrical signal is transmitted to the processor and obtained as the terahertz near-field signal of the sample to be measured after phase-locked demodulation processing. Based on this terahertz near-field signal, terahertz near-field spectral imaging is performed in the atomic force microscope unit. The atomic force microscope unit includes: an atomic force probe, a quadrant laser emitter, a quadrant detector, and a sample stage. The quadrant laser emitter is used to emit a laser to the tip cantilever of the atomic force probe, and the laser is reflected back to the quadrant detector after passing through the tip cantilever. The sample stage is a hollow stage, and the sample is suspended in the hollow area of the sample stage. The Raman spectrometer includes: a light source, a first band-pass filter, a mirror, a heat dissipation light collection system, a second band-pass filter, a notch filter, several plane mirrors, an edge filter, a focusing lens, a spectrometer adjustable slit, a collimating mirror, a reflecting focusing mirror, a grating, a cylindrical mirror, a CCD detector, and a processor; Among them, the laser emitted by the light source is filtered by the first band-pass filter and then reflected by the reflecting mirror onto the sample to be measured. The laser irradiates the sample to be measured to generate Raman scattered light. The Raman scattered light is collected by the heat dissipation light collection system and then enters the second band-pass filter. After being filtered by the second band-pass filter, it enters the notch filter. After being filtered by the notch filter, it enters the focusing lens. The focusing lens converges the signal to the adjustable slit of the spectrometer. The signal exits from the adjustable slit of the spectrometer and then enters the collimating mirror. The signal is collimated by the collimating mirror and then refracted to the reflecting surface of the reflecting focusing mirror. The signal is reflected by the reflecting surface of the reflecting focusing mirror to the grating. The grating disperses the Raman scattered light carrying the signal of the sample to be measured. The dispersed signal enters the focusing surface of the reflecting focusing mirror to converge the signal and then to the cylindrical mirror for astigmatism correction. The corrected signal is received by the CCD detector for its spectral information, and the spectral information is transmitted to the processor for processing after being received.

2. The terahertz near-field microscope system based on a Raman spectrometer according to claim 1, characterized in that, The reflecting focusing mirror includes 5 surfaces, namely the top surface, the bottom surface, 2 side surfaces and the back surface. Among them, the top surface and the bottom surface are parallel to each other. One of the 2 side surfaces is a plane mirror, and the other is a parabolic focusing mirror.

3. The terahertz near-field microscope system based on a Raman spectrometer according to claim 1, characterized in that, The first band-pass filter is used to filter the direct light in the laser. The second band-pass filter, the notch filter and the edge filter are all used to filter the scattered light in the Raman scattered light.

4. The terahertz near-field microscope system based on a Raman spectrometer according to claim 1, characterized in that, The adjustable slit of the spectrometer is used for spatial filtering. The width of the adjustable slit of the spectrometer can be adjusted and the width of the adjustable slit of the spectrometer can be adjusted in the horizontal direction or the vertical direction.

5. The terahertz near-field microscope system based on a Raman spectrometer according to claim 1, characterized in that, The filters in the second band-pass filter, the edge filter and the notch filter are all narrow-band filters.

6. The terahertz near-field microscope system based on a Raman spectrometer according to claim 5, characterized in that, The central wavelength of the narrow-band filter is 785 ± 3 nm, the bandwidth is 10 nm, and the cut-off range is 200 - 1200 nm.

7. A method for using the terahertz near-field microscope system based on a Raman spectrometer according to any one of claims 1-6, characterized in that, The method includes: Step 1: Debug the system. After debugging is completed, turn on the system power supply. Step 2: Fix the sample to be measured on the sample stage through the clip. Step 3: Turn on the four-quadrant laser emitter. Adjust the angle of the four-quadrant laser emitter so that the four-quadrant detector can receive the reflected signal. Approach the atomic force probe to the sample to be measured. Turn on the femtosecond laser light source. Feed the scattered terahertz near-field signal back to the lock-in amplifier through the receiving antenna via the voltage amplifier. Transmit the amplified signal to the processor for near-field imaging. Step 4: Turn on the light source in the Raman spectrometer. The laser emitted by the light source is processed and then irradiated onto the sample to be measured to generate Raman scattered light. The processed signal of the Raman scattered light is received by the CCD detector for its spectral information, and the spectral information is transmitted to the processor for processing to display the spectral result.

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