A terahertz time-domain spectroscopy near-field imaging device and imaging method

Abstract

The application discloses a terahertz time-domain spectroscopy near-field imaging device and an imaging method.The imaging device comprises a probe assembly, the probe assembly comprises a first substrate, a second substrate is arranged on the first substrate, the second substrate is used for generating photo-generated carriers under irradiation of laser in free space, an electrode array, a cantilever, a grounding electrode and a first gap between the cantilever and the grounding electrode are arranged on the second substrate, the cantilever is connected with a needle tip and the electrode array, the electrode array comprises a plurality of electrodes, a second gap exists between two adjacent electrodes, and the plurality of electrodes are connected to a post-processing unit through an analog switch. According to the application, the terahertz near-field time-domain signal and the spectrum diagram can be obtained without arranging a mechanical delay line, the complexity and the space occupancy of the system are greatly reduced, meanwhile, since the analog switch has a high on-off rate, a faster time-domain signal refresh rate can be obtained, and compared with a traditional mechanical delay line step sampling scanning, the scanning time is greatly shortened.

Description

Technical Field

[0001] This invention relates to the field of terahertz imaging, and more specifically to a terahertz time-domain spectroscopy near-field imaging device and imaging method. Background Technology

[0002] Terahertz (THz) waves typically refer to electromagnetic waves with frequencies ranging from 100 GHz to 10 THz and wavelengths from 30 to 3000 μm. Located between millimeter waves and far-infrared rays in the electromagnetic spectrum, they possess low radiation, strong penetrability, and the optical property of easily resonating with biological and semiconductor materials. These characteristics have led to the widespread application of terahertz near-field imaging technology in fields such as security inspection, chemical identification, medical imaging, and quality control. In recent years, with the gradual maturation of terahertz frequency signal sources and detection methods, terahertz scanning near-field optical microscopy (THz-SNOMs) technology has developed rapidly.

[0003] Terahertz scanning near-field optical microscopy techniques can be broadly categorized into scattering-based THz-SNOMs, aperture-based THz-SNOMs, and terahertz time-domain spectroscopy SNOMs. Among these, terahertz time-domain spectroscopy SNOMs represent a technique that breaks the terahertz diffraction limit, based on terahertz time-domain spectrometers (THz-TDS) and atomic force microscopes (AFM).

[0004] Traditional terahertz time-domain spectroscopy (SNOMs) methods for acquiring time-domain signals and spectra involve using mechanical delay lines to adjust the optical path difference to sample signals at different time delay positions. After demodulation by a lock-in amplifier, a Fourier transform is performed to obtain the sample's spectral information. However, in traditional methods, the mechanical delay lines not only increase the complexity and size of the system, but the limitation of the electrode response speed of these lines also results in a scanning frequency of only tens of hertz within the terahertz peak range, leading to a low time-domain signal refresh rate.

[0005] Therefore, it is necessary to design a new terahertz time-domain spectroscopy near-field imaging device and imaging method. Summary of the Invention

[0006] One objective of this invention is to provide a terahertz time-domain spectral near-field imaging device, which, by improving the probe assembly, can process the terahertz signal carrying sample information transmitted on the tip of the probe assembly. After processing, the terahertz near-field spectrum corresponding to the terahertz signal within the electrode array range is obtained, thereby eliminating the need for traditional mechanical delay lines, reducing system complexity, improving the refresh rate of the time-domain signal, and saving scanning time.

[0007] Specifically, the above objective is achieved through the following technical solution:

[0008] A terahertz time-domain spectroscopy near-field imaging device includes a probe assembly. The probe assembly includes a first substrate, on which a second substrate is disposed. The second substrate is used to generate photogenerated carriers under irradiation by a laser in free space. An electrode array, a cantilever, a ground electrode, and a first gap located between the cantilever and the ground electrode are disposed on the second substrate. The cantilever connects the probe tip and the electrode array. The electrode array includes a plurality of electrodes, and a second gap exists between adjacent electrodes. The plurality of electrodes are connected to a post-processing unit via an analog switch.

[0009] In this technical solution, the probe assembly of the imaging device has been improved. Specifically, the probe assembly includes a first substrate, which is preferably a ceramic substrate. A second substrate is disposed on the first substrate, and the second substrate is capable of generating photogenerated carriers under laser irradiation in free space. In one or more embodiments, the second substrate can be one or more of LT-GaAs, GaAs, InP, InGaAs, and Si-GaAs, or other materials capable of generating photogenerated carriers under laser irradiation. Preferably, the second substrate is LT-GaAs.

[0010] A cantilever is disposed on the second substrate, and a ground electrode is deposited thereon, with a first gap between the ground electrode and the cantilever. When the incident terahertz wave is focused between the sample and the tip, the terahertz signal containing sample information directly acquired by the tip is transmitted along the tip and cantilever in the form of an ultrafast current to the range of the electrode array.

[0011] The electrode array comprises multiple equally spaced electrodes, preferably gold electrodes. A second gap exists between adjacent electrodes. The electrodes in the electrode array correspond to terahertz signals at different positions on the cantilever. Each electrode in the electrode array is connected to an input channel of an analog switch. Controlling the on / off state of the analog switch transmits the current signals generated by each electrode to a post-processing unit for acquisition, processing, and analysis, ultimately obtaining a terahertz near-field spectrum containing sample information. In one or more embodiments, the analog switch is a CMOS circuit. In some preferred embodiments, the analog switch shares a common ground with the ground electrode.

[0012] During operation, the incident terahertz wave is focused between the sample and the needle tip, forming an electric dipole system. The incident terahertz wave is locally enhanced at the needle tip, generating a terahertz current signal that propagates along the needle tip and cantilever. When this terahertz current signal propagates along the cantilever to the ground electrode side, an electric field is formed within the first gap. Simultaneously, the second substrate within the first gap generates photogenerated carriers under the irradiation of a laser in free space. These photogenerated carriers move directionally under the influence of the electric field, forming a current. The analog switch is controlled to traverse the electrode array, collecting the current at the cantilever position corresponding to each electrode, thereby obtaining the terahertz signal within the electrode array range. Finally, the voltage sequence collected by each electrode is Fourier transformed to obtain the terahertz near-field spectrum.

[0013] By improving the probe assembly, this imaging device can obtain terahertz near-field time-domain signals and spectrograms without the need for mechanical delay lines, greatly reducing system complexity and space occupancy. Simultaneously, due to the high switching rate of the analog switch, a faster time-domain signal refresh rate can be achieved, significantly shortening the scanning time compared to traditional mechanical delay line step sampling scanning. Furthermore, this technical solution extracts the conducted terahertz signal directly from the needle tip, discarding the scattered field. Compared to the traditional method of collecting signals from the needle tip and extracting scattered signals in the far field, the terahertz signal conducted along the needle tip, cantilever, or other metal components contains more near-field information, significantly improving the signal-to-noise ratio and extraction efficiency.

[0014] Furthermore, the width of the first gap is 5–15 μm. The width of the gap determines the strength of the acquired current signal; a narrower gap results in a higher concentration of photogenerated carriers in the medium and a faster generation of the space charge electric field. However, in high-energy optical pumping, the saturation problem caused by carrier space charge and radiation field shielding needs to be considered. Simultaneously, an excessively narrow gap will lead to excessive voltage, causing electrode breakdown. This places higher demands on electrode insulation, bias voltage, and light intensity. Preferably, the gap width is 8–11 μm; more preferably, the gap width is 10 μm.

[0015] Furthermore, the thickness of the second substrate is 1.0–1.5 μm. The thickness of the second substrate determines the generation of photogenerated carriers. If it is too thin, the resulting carrier concentration will be insufficient, leading to a weak antenna saturation signal, making it impossible to distinguish and extract useful signals in subsequent data acquisition. If the substrate is too thick, it will significantly increase the equipment cost, and a thick substrate requires stronger femtosecond laser excitation, which can easily damage the device. Preferably, the thickness of the second substrate is 1.0–1.3 μm, and more preferably, the thickness of the second substrate is 1.2 μm.

[0016] Furthermore, the width of the second gap is 1–10 μm. The second gap and the electrode width affect the time resolution of terahertz signal acquisition. When the electrode is small enough, the smaller the gap, the higher the time resolution. However, an excessively small gap will cause processing difficulties and may lead to electrode breakdown. Therefore, in this technical solution, the width of the second gap is determined to be 1–10 μm. Preferably, the width of the second gap is 1–8 μm, and more preferably, the thickness of the second substrate is 1–1.5 μm.

[0017] Furthermore, the bottom end of the second gap extends onto the first substrate. In this technical solution, the bottom end of the second gap directly penetrates the second substrate and extends to the first substrate, thereby avoiding the generation of photogenerated carriers within the second gap and reducing carrier interference.

[0018] Furthermore, the system also includes a laser unit comprising a laser for generating a femtosecond laser and a coupler for splitting the femtosecond laser into a pump laser and a probe laser. After the laser generates a femtosecond laser with a specific center wavelength and power, the femtosecond laser is split into a pump laser and a probe laser by the coupler. In one or more embodiments, the femtosecond laser may also be split by other beam-splitting elements such as a beam splitter. In one or more embodiments, an attenuator is also provided between the laser and the coupler, the attenuator being used to adjust the power of the femtosecond laser to prevent damage to subsequent components.

[0019] Furthermore, it also includes an incident unit, which includes a photoconductive antenna for generating an incident terahertz wave based on the pump laser, and an off-axis mirror for focusing the incident terahertz wave. The incident terahertz wave is used to focus between the sample and the tip to form a terahertz signal containing sample information. The terahertz signal is conducted along the tip and cantilever, and forms an electric field in the first gap when it is conducted to the side of the ground electrode.

[0020] In this technical solution, the incident unit generates an incident terahertz wave under the excitation of the pump laser, and focuses the incident terahertz wave between the sample and the tip of the probe assembly to form a terahertz signal containing sample information. The terahertz signal is propagated along the tip and cantilever, and an electric field is formed in the first gap between the cantilever and the ground electrode when it is propagated to one side. Since an analog switch is used to traverse the voltage collected by each electrode, the incident unit of the imaging device does not need to set a mechanical delay line to adjust the optical path difference. At the same time, the transmission distance of the laser in free space is shortened, and no additional compensation for optical path and pulse width is required.

[0021] Furthermore, it also includes a detection unit, which includes an optical fiber collimator for converting the detection laser into a free-space laser. The free-space laser is used to irradiate a second substrate located within the first gap to generate photogenerated carriers, which are used to form a current under the action of an electric field.

[0022] In this technical solution, the fiber collimator of the detection unit is used to convert the detection laser into a free-space laser to irradiate the second substrate in the entire first gap to form photogenerated carriers. After the photogenerated carriers are formed, they move directionally under the influence of the electric field formed in the first gap to form a current. The current at each point of the cantilever is transmitted to the post-processing unit after being connected by the analog switch through the electrodes in the electrode array.

[0023] Furthermore, the post-processing unit includes a host computer, a data acquisition card, and a current amplifier electrically connected to the analog switch. The current amplifier is used to amplify the current from any channel of the analog switch and convert the current into voltage. The data acquisition card is used to acquire the voltage, and the host computer is used to process the acquired voltage to obtain sample information.

[0024] In this technical solution, each electrode in the electrode array is connected to the input channel of the analog switch, and the output of the analog switch is connected to the current amplifier. The terahertz signal at that location can be obtained by acquiring the signal through the data acquisition card. The analog switch is controlled to traverse the electrode array, thereby obtaining the terahertz signal within the range of the electrode array. The host computer performs a Fourier transform on the voltage sequence measured by each electrode in the electrode array to obtain the terahertz near-field spectrum.

[0025] Another objective of this invention is to provide an imaging method based on any of the aforementioned terahertz time-domain spectroscopy near-field imaging devices, which utilizes the characteristic of rapid switching of the electrode array to significantly improve the time-domain signal refresh rate and greatly shorten the scanning time compared to the traditional mechanical delay line step sampling scan.

[0026] Specifically, the above objective is achieved through the following technical solution:

[0027] A terahertz time-domain spectroscopy near-field imaging method, employing any of the aforementioned terahertz time-domain spectroscopy near-field imaging devices, the imaging method comprising the following steps:

[0028] Femtosecond laser beam splitting consists of a pump laser and a probe laser;

[0029] The pump laser excites and generates an incident terahertz wave, which is then focused between the sample and the needle tip to form a terahertz signal containing sample information.

[0030] When the terahertz signal is conducted along the needle tip and cantilever to the range of the electrode array, an electric field is formed in the first gap;

[0031] The probe laser is converted into a free-space laser and irradiates the second substrate within the first gap to generate photogenerated carriers. The photogenerated carriers form a current under the action of the electric field.

[0032] Sample information is obtained by collecting and processing the current of each electrode in the electrode array.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] 1. This invention can obtain terahertz near-field time-domain signals and spectrum diagrams without setting mechanical delay lines, which greatly reduces the complexity and space occupancy of the system. At the same time, since the analog switch has a high switching rate, a faster time-domain signal refresh rate can be obtained, which significantly shortens the scanning time compared with the traditional mechanical delay line step sampling scan.

[0035] 2. This invention extracts the terahertz signal directly from the needle tip, discarding the scattered field. Compared with the traditional method of collecting the scattered signal from the needle tip and extracting it in the far field, the terahertz signal conducted along the needle tip, cantilever, and other metals contains more near-field information, which can significantly improve the signal-to-noise ratio and increase the extraction efficiency.

[0036] 3. The present invention connects the bottom end of the second gap to the upper surface of the first substrate, which can avoid the generation of photogenerated carriers in the second gap and reduce carrier interference. Attached Figure Description

[0037] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0038] Figure 1 This is a schematic diagram of the probe assembly in a specific embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the electrode array structure in a specific embodiment of the present invention;

[0040] Figure 3 This is a structural block diagram of a terahertz time-domain spectroscopy near-field imaging device in a specific embodiment of the present invention;

[0041] Figure 4 This is a flowchart of the terahertz time-domain spectroscopy near-field imaging method in a specific embodiment of the present invention;

[0042] Figure 5 This is a model interface used for simulation in a specific embodiment of the present invention, where the letter 'a' represents the terahertz wave incident on the needle tip, and the numbers 'bj' represent the needle tip and the first to ninth current loops on the cantilever, respectively.

[0043] Figure 6 The terahertz wave incident on the needle tip in a specific embodiment of the present invention;

[0044] Figure 7 The terahertz waves are the first to ninth current loops on the needle tip and cantilever in a specific embodiment of the present invention.

[0045] The attached diagram shows the markings and corresponding component names:

[0046] 1-First substrate, 2-Second substrate, 3-Cantilever, 4-Needle tip, 5-Ground electrode, 6-First gap, 7-Electrode array, 71-Electrode, 72-Second gap, 8-Sample;

[0047] 11-Laser unit, 12-Incident unit, 13-Detection unit, 14-Probe assembly, 15-Analog switch, 16-Post-processing unit. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0049] In the description of this invention, it should be understood that the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0050] The term "connection" as used in this invention, unless otherwise specified, can refer to a direct connection or an indirect connection via other components.

[0051] The terms "first," "second," etc., used in this invention (e.g., first substrate, second substrate, first gap, second gap, etc.) are merely for the purpose of clarity in description and are not intended to limit any order or emphasize importance.

[0052] Example 1:

[0053] like Figures 1 to 3The terahertz time-domain spectroscopy near-field imaging device shown includes a probe assembly 14, which includes a first substrate 1 and a second substrate 2 disposed on the first substrate 1. The second substrate 2 is used to generate photogenerated carriers under the irradiation of a laser in free space. The second substrate 2 is provided with an electrode array 7, a cantilever 3, a ground electrode 5, and a first gap 6 located between the cantilever 3 and the ground electrode 5. The cantilever 3 connects the probe tip 4 and the electrode array 7. The electrode array 7 includes a plurality of electrodes 71, and a second gap 72 exists between two adjacent electrodes 71. The plurality of electrodes 71 are connected to a post-processing unit via an analog switch 15.

[0054] In one or more embodiments, the second substrate may be one or more of LT-GaAs, GaAs, InP, InGaAs, and Si-GaAs, or other materials capable of generating photogenerated carriers under laser irradiation. Preferably, the second substrate is LT-GaAs.

[0055] In one or more embodiments, the analog switch is a CMOS circuit. In some preferred embodiments, the analog switch shares a common ground with the ground electrode.

[0056] In some embodiments, the first substrate is a ceramic substrate with dimensions of 1000*500*100μm. In one or more embodiments, the grounding electrode deposited on the second substrate has dimensions of 800*65.55*8.37μm.

[0057] In some preferred embodiments, the width of the first gap is 5–15 μm. Preferably, the width of the first gap is 8–11 μm, and more preferably, the width of the first gap is 10 μm.

[0058] In some preferred embodiments, the thickness of the second substrate is 1.0–1.5 μm. Preferably, the thickness of the second substrate is 1.0–1.3 μm, and more preferably, the thickness of the second substrate is 1.2 μm. In one or more embodiments, the dimensions of the second substrate are 800*200*1.2 μm.

[0059] In some preferred embodiments, the electrodes 71 in the electrode array are gold electrodes, preferably with dimensions of 30*5*0.1μm. The width of the second gap between two adjacent electrodes 71 is preferably 1-8μm, more preferably 1-1.5μm.

[0060] In one or more embodiments, the length of the needle tip 4 is 20 μm and the radius of curvature of the needle tip is less than 20 nm.

[0061] In some preferred embodiments, to prevent the carriers generated in the second gap from affecting the directional flow of carriers in the first gap, the bottom end of the second gap 72 extends onto the first substrate 1.

[0062] During operation, the incident terahertz wave is focused between the sample and the needle tip, forming an electric dipole system. The incident terahertz wave is locally enhanced at the needle tip, generating a terahertz current signal that propagates along the needle tip and cantilever. When this terahertz current signal propagates along the cantilever to the ground electrode side, an electric field is formed within the first gap. Simultaneously, the second substrate within the first gap generates photogenerated carriers under the irradiation of a laser in free space. These photogenerated carriers move directionally under the influence of the electric field, forming a current. The analog switch is controlled to traverse the electrode array, collecting the current at the cantilever position corresponding to each electrode, thereby obtaining the terahertz signal within the electrode array range. Finally, the voltage sequence collected by each electrode is Fourier transformed to obtain the terahertz near-field spectrum.

[0063] Example 2:

[0064] Based on Example 1, such as Figure 3 The terahertz time-domain spectroscopy near-field imaging device shown also includes a laser unit 11, an incident unit 12, and a detection unit 13. The laser unit 11 includes a laser for generating a femtosecond laser and a coupler for splitting the femtosecond laser into a pump laser and a detection laser.

[0065] The incident unit 12 includes a light guide antenna for generating an incident terahertz wave based on the pump laser, and an off-axis mirror for focusing the incident terahertz wave. The incident terahertz wave is focused between the sample 8 and the tip 4 to form a terahertz signal containing sample information. The terahertz signal is conducted along the tip 4 and the cantilever 3, and forms an electric field in the first gap 6 when it is conducted to the side of the ground electrode 5.

[0066] The detection unit 13 includes an optical fiber collimator for converting the detection laser into a free-space laser. The free-space laser is used to irradiate the second substrate 2 located within the first gap 6 to generate photogenerated carriers. The photogenerated carriers are used to form a current under the action of an electric field.

[0067] In some preferred embodiments, the post-processing unit includes a host computer, a data acquisition card, and a current amplifier electrically connected to the analog switch 15. The current amplifier is used to amplify the current from any channel of the analog switch 15 and convert the current into voltage. The data acquisition card is used to acquire the voltage, and the host computer is used to process the acquired voltage to obtain sample information.

[0068] Example 3:

[0069] Based on the above embodiments, such as Figure 4 The terahertz time-domain spectroscopy near-field imaging method shown includes the following steps:

[0070] Femtosecond laser beam splitting consists of a pump laser and a probe laser;

[0071] The pump laser excites and generates an incident terahertz wave, which is focused between the sample 8 and the tip 4 to form a terahertz signal containing sample information.

[0072] When the terahertz signal is conducted along the needle tip 4 and cantilever 3 to the range of the electrode array 7, an electric field is formed in the first gap 6;

[0073] The probe laser is converted into a free-space laser and irradiates the second substrate 2 within the first gap 6 to generate photogenerated carriers. The photogenerated carriers form a current under the action of the electric field.

[0074] The sample information of sample 8 is obtained by collecting and processing the current of each electrode 71 in electrode array 7.

[0075] like Figure 5 As shown, after the incident terahertz wave from the left illuminates the needle tip on the right, as... Figure 6 and Figure 7 As shown, terahertz waves were generated at each current loop of the needle tip and cantilever, indicating that the terahertz signal containing sample information can be transmitted along the needle tip and cantilever. This application utilizes a probe assembly improved by this property to directly extract the conducted terahertz signal from the needle tip, discarding the scattered field. This not only improves the signal-to-noise ratio but also eliminates the need for mechanical delay lines to obtain the terahertz near-field time-domain signal and spectrum, significantly reducing system complexity and space occupancy. Furthermore, due to the high switching rate of the analog switch, a faster time-domain signal refresh rate can be achieved, significantly shortening the scanning time compared to traditional mechanical delay line step sampling scanning.

[0076] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A terahertz time-domain spectroscopy near-field imaging device, comprising a probe assembly (14), characterized in that, The probe assembly (14) includes a first substrate (1), on which a second substrate (2) is disposed. The second substrate (2) is used to generate photogenerated carriers under the irradiation of a laser in free space. The second substrate (2) is provided with an electrode array (7), a cantilever (3), a ground electrode (5), and a first gap (6) located between the cantilever (3) and the ground electrode (5). The cantilever (3) connects the tip (4) and the electrode array (7). The electrode array (7) includes a plurality of electrodes (71), and there is a second gap (72) between two adjacent electrodes (71). The bottom end of the second gap (72) extends to the first substrate (1). The plurality of electrodes (71) are connected to a post-processing unit via an analog switch (15).

2. The terahertz time-domain spectral near-field imaging device according to claim 1, characterized in that, The width of the first gap (6) is 5~15 μm.

3. The terahertz time-domain spectral near-field imaging device according to claim 1, characterized in that, The thickness of the second substrate (2) is 1.0~1.5μm.

4. The terahertz time-domain spectral near-field imaging device according to claim 1, characterized in that, The width of the second gap (72) is 1~10 μm.

5. A terahertz time-domain spectral near-field imaging device according to any one of claims 1 to 4, characterized in that, It also includes a laser unit (11), which includes a laser for generating a femtosecond laser and a coupler for splitting the femtosecond laser into a pump laser and a probe laser.

6. A terahertz time-domain spectral near-field imaging device according to claim 5, characterized in that, It also includes an incident unit (12), which includes a light guide antenna for generating an incident terahertz wave based on the pump laser, and an off-axis mirror for focusing the incident terahertz wave. The incident terahertz wave is focused between the sample (8) and the tip (4) to form a terahertz signal containing sample information. The terahertz signal is conducted along the tip (4) and the cantilever (3) and forms an electric field in the first gap (6) when it is conducted to the side of the ground electrode (5).

7. A terahertz time-domain spectral near-field imaging device according to claim 5, characterized in that, It also includes a detection unit (13), which includes an optical fiber collimator for converting the detection laser into a free-space laser. The free-space laser is used to irradiate the second substrate (2) located in the first gap (6) to generate photogenerated carriers. The photogenerated carriers are used to form a current under the action of an electric field.

8. A terahertz time-domain spectral near-field imaging device according to claim 5, characterized in that, The post-processing unit includes a host computer, a data acquisition card, and a current amplifier electrically connected to the analog switch (15). The current amplifier is used to amplify the current from any channel of the analog switch (15) and convert the current into voltage. The data acquisition card is used to acquire the voltage, and the host computer is used to process the acquired voltage to obtain the sample information contained therein.

9. A terahertz time-domain spectral near-field imaging method, characterized in that, The imaging method using a terahertz time-domain spectroscopy near-field imaging device according to any one of claims 1 to 8 includes the following steps: Femtosecond laser beam splitting consists of a pump laser and a probe laser; The pump laser excites and generates an incident terahertz wave, which is focused between the sample (8) and the tip (4) to form a terahertz signal containing sample information; When the terahertz signal is conducted along the needle tip (4) and cantilever (3) to the range of the electrode array (7), an electric field is formed in the first gap (6); The probe laser is converted into a free space laser and irradiates the second substrate (2) in the first gap (6) to generate photogenerated carriers. The photogenerated carriers form a current under the action of the electric field. The sample information of sample (8) is obtained by collecting and processing the current of each electrode (71) in the electrode array (7).

Images