Preparation method of high-sensitivity terahertz metasurface dual-mode sensor

Abstract

The invention discloses a preparation method of a high-sensitivity terahertz metasurface dual-mode sensor, and belongs to the field of terahertz biochemical sensing. The terahertz metasurface sensor is prepared in the mode that the dielectric layer is firstly patterned and then overall coating is conducted, the liquid thickness can be accurately controlled to be in the micron order through the patterned dielectric layer, when a biological sample solution is detected, THz wave absorption is reduced by reducing the amount of liquid to be detected, and the detection accuracy is improved. Therefore, the test problem caused by THz wave strong absorption of the polar liquid to be tested is solved to a certain extent; meanwhile, due to the design of the graphical dielectric layer, the volume of an overlapped area of the sample and strong field energy is increased, the terahertz wave-substance interaction is greatly enhanced, and higher device sensitivity is achieved. In addition, the dual-mode sensor prepared by the method can generate perfect absorption peaks of two modes at the same time under oblique incidence excitation of terahertz waves, and the two modes have good angle robustness and high performance under excitation of TE / TM waves.

Description

Technical Field

[0001] The present invention relates to the field of solution / liquid / biological sample detection and terahertz biochemical sensing, and in particular to a method for preparing a high-sensitivity terahertz supersurface dual-mode sensor. Background Art

[0002] Terahertz waves (frequency 0.1THz-10THz, wavelength 3mm-0.03mm) are electromagnetic waves with frequencies between microwave bands and infrared bands, and have both electronic and optical properties. Terahertz waves have unique properties such as low photon energy, strong penetration, and biomacromolecule fingerprints, which make them have great application potential in the field of biological sample detection. However, free-space terahertz spectroscopy technology still has technical bottlenecks that limit its performance improvement and widespread application, such as the weak interaction between free-space terahertz waves and biochemical substances, and the strong absorption of terahertz waves by polar liquids such as water.

[0003] Electromagnetic metamaterials are artificial materials that do not exist in nature. They are composed of subwavelength unit structure arrays (such as periodic) and can manipulate electromagnetic waves by controlling the unit structure design and array arrangement (such as arrangement period). They can even exhibit unique electromagnetic properties that natural materials do not have, such as negative dielectric constant / permeability / refractive index and local field enhancement. The metasurface is essentially a two-dimensional metamaterial. The emergence of terahertz electromagnetic metasurfaces provides a new technical approach to achieve high-performance terahertz biochemical sensing. In recent years, terahertz metasurface sensors have shined in the field of biological sample sensing and detection.

[0004] In practical applications, the refractive index of most biological samples is between 1.3 and 1.4, and the difference in refractive index is very small. For example, the refractive index of normal cells is 1.30 to 1.35, and the refractive index of cancerous cells is 1.39 to 1.40. In order to achieve accurate detection of these biological samples, it is necessary to design a terahertz metasurface biochemical sensor with ultra-high sensitivity. Sufficient terahertz wave-matter interaction is the guarantee of the high sensitivity of the sensor, that is, the biological sample to be tested needs to be placed in the area with the strongest field energy of the sensor.

[0005] In 2016, ACS Photonics, Volume 3, Issue 12, page 2308, reported a terahertz reflective metasurface sensor that achieved trace detection of avidin with a device sensitivity of 0.01 THz / RIU; in 2016, Laser & Photonics Reviews, Volume 6, Issue 10, page 962, reported a sensor structure that integrated a microfluidic channel into a terahertz absorber. By controlling the thickness of the liquid to reduce the absorption of terahertz waves, it greatly enhanced the interaction between the liquid sample to be tested and the terahertz wave, and achieved a measured sensitivity of 0.22 THz / RIU; in 2021, Biosensors and Bioelectronics, Volume 185, page 113241, reported a transmission-type terahertz metasurface sensor based on an electromagnetically induced transparency effect, which achieved detection of glioma cells of different types and concentrations, with a simulated sensitivity of up to 0.496 THz / RIU.

[0006] At present, a large part of the strong field energy of terahertz metasurface sensors (as mentioned above) is localized in the dielectric layer / substrate and cannot fully contact the sample, which limits the terahertz wave-matter interaction and thus the device sensitivity. In addition, most of them are single sensing modes, and the device reliability and robustness are low. At the same time, microfluidic devices for liquid sample detection also have problems such as large device size, complex process, and high processing cost. This series of problems limits the practical application and future development of terahertz metasurface biochemical sensors. Summary of the invention

[0007] In view of the above problems in the prior art, the present invention proposes a method for preparing a high-sensitivity terahertz metasurface dual-mode sensor, which can achieve the sensitivity enhancement effect of the dual-mode sensor and is conducive to achieving higher device sensitivity.

[0008] The technical solution proposed by the present invention is as follows:

[0009] A method for preparing a high-sensitivity terahertz metasurface dual-mode sensor, the steps comprising:

[0010] 1) Clean the base layer, use acetone, isopropanol and water to clean it in sequence, then dry it, and then electron beam evaporate\magnetron sputter the adhesion layer and the metal reflective layer in sequence to form a substrate;

[0011] 2) Patterning the dielectric layer using MEMS processing technology; the material of the patterned dielectric layer is an oxide dielectric material or a polymer dielectric material with a low dielectric constant, and the thickness is h3 = 1 μm to 20 μm;

[0012] 3) Electron beam evaporation\magnetron sputtering is used to sequentially deposit an adhesion layer and a metal layer, and the metal layer is deposited on the patterned dielectric layer to form a terahertz metal microarray layer, thereby completing the preparation of a high-sensitivity dual-mode terahertz metasurface.

[0013] Furthermore, if the dielectric layer is made of a polymer dielectric material, step 2) specifically includes:

[0014] 2-2) cleaning the substrate, sequentially washing with acetone, isopropanol and water, drying, and coating with a tackifier to increase the adhesion and stability of the photosensitive PI glue;

[0015] 2-3) After the photosensitive PI glue is spin-coated on the substrate, it is pre-baked, then UV-lithography is performed, and it is rinsed with a developer and a cleaning solution in sequence to achieve patterning of the photosensitive PI glue;

[0016] 2-4) Baking the substrate in the above step in a nitrogen environment (low oxygen environment) to remove the residual solvent and photosensitive components in the photosensitive PI glue, enhance the adhesion of the dielectric layer, and realize the imidization of the precursor into polyimide.

[0017] Furthermore, if the dielectric layer is made of oxide dielectric material, step 2) specifically includes:

[0018] 2-5) depositing a micron-sized oxide dielectric layer by chemical vapor deposition (PECVD) process;

[0019] 2-6) washing with acetone, ethanol and water in sequence, drying, and coating with a tackifier to increase the adhesion and stability of the photoresist;

[0020] 2-7) Spin-coating photoresist, and performing UV photolithography and development;

[0021] 2-8) Electron beam evaporation\magnetron sputtering to deposit a hard mask of a certain thickness;

[0022] 2-9) removing excess photoresist and performing dry etching until the metal layer stops;

[0023] 2-10) Release the excess hard mask.

[0024] Furthermore, the substrate is a common substrate such as silicon, quartz, etc., and the thickness h1 = 100 μm to 500 μm.

[0025] Furthermore, the adhesion layer is made of Cr / Ti and has a thickness of about 5 to 10 nm. Its main function is to adhere to the upper layer material to stabilize the structure.

[0026] Furthermore, the metal reflective layer is a common metal film such as Au, Ag, Al, Cu, etc. with a thickness of h2 = 100nm to 250nm.

[0027] Furthermore, the terahertz metal microarray layer is made of common metals such as Au, Ag, Al, Cu, etc., and has a thickness of h4=100 μm to 250 μm.

[0028] Furthermore, the resonant unit in the terahertz metal microarray is in the shape of a hollow square ring, with a periphery length / width L=20 μm to 100 μm, a square ring line width w=2 μm to 30 μm, and a period P x =P y =40μm~200μm.

[0029] The technical effects of the present invention are as follows:

[0030] The present invention utilizes MEMS processing technology to pattern the dielectric layer. When a terahertz metasurface sensor is used to detect a biological sample solution, the patterned dielectric layer can accurately control the liquid thickness at the μm level, and reduce the absorption of THz waves by reducing the amount of liquid to be tested, thereby solving the testing problem caused by the strong absorption of THz waves by polar liquid to be tested to a certain extent; at the same time, the design of the patterned dielectric layer increases the volume of the overlapping area between the sample and the strong field energy, greatly improving the terahertz wave-matter interaction and achieving higher device sensitivity.

[0031] In addition, compared with the traditional "Metal-Insulator-Metal (MIM)" reflective terahertz metasurface sensor structure, the present invention uses MEMS processes such as etching / photolithography, and adopts the method of first patterning the dielectric layer and then coating the entire structure to realize the processing of the top periodic structure. The sensor prepared by the present invention has two different high-sensitivity sensing modes. Mode 1 is located at low frequency (f1), which is a perfect absorption mode caused by the equivalent impedance matching of the top periodic structure with the free space and Fabry-Perot (FP) resonance; Mode 2 is located at high frequency (f2), which is a bound state mode (Q-BIC) in the quasi-continuous domain caused by the phase asymmetry introduced by the incident angle. The sensing sensitivity of these two modes is greatly improved compared with the sensitivity of traditional transmissive / reflective terahertz metasurface sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a process flow chart of the present invention for preparing a high-sensitivity terahertz metasurface dual-mode sensor (taking oxide dielectric material as the dielectric layer, such as SiO2 as an example);

[0033] Figure 2 It is a process flow chart of the present invention for preparing a high-sensitivity terahertz metasurface dual-mode sensor (taking a polymer as a dielectric layer, such as PI as an example).

[0034] Figure 3 It is a schematic diagram of the structure of a high-sensitivity terahertz metasurface dual-mode sensor prepared by the present invention.

[0035] Figure 4 It is a schematic diagram of the structure of the hollow ring unit of the super surface in a specific embodiment of the present invention.

[0036] Figure 5 It is a schematic diagram of sample distribution after the dual-mode sensor prepared by the present invention is loaded with a liquid sample.

[0037] Figure 6 It is a performance simulation of the dual-mode terahertz reflective metasurface sensor prepared by the present invention; wherein (a) is the simulated absorption spectrum of the proposed high-sensitivity weakened substrate-enhanced terahertz metasurface dual-mode sensor under TE wave excitation (45° incident angle), and (b) is the simulated reflection spectrum of the proposed high-sensitivity weakened substrate-enhanced terahertz metasurface dual-mode sensor under TM wave excitation (45° incident angle).

[0038] Figure 7 It is an angular heat map of two sensing resonance peaks of the dual-mode terahertz reflective metasurface sensor prepared by the present invention.

[0039] Among them, (a) is the angular heat map of the proposed THz metasurface dual-mode sensor under TE wave excitation (incident angle of 0°~80°); (b) is the angular heat map of the proposed THz metasurface dual-mode sensor under TM wave excitation (incident angle of 0°~80°).

[0040] Figure 8 The surface current distribution diagram at two sensing resonance peak frequency points of the dual-mode terahertz reflective metasurface sensor prepared by the present invention (under TE wave 45° incident angle excitation, the electric field strength scale range is 0V / m~4×10 6 V / m). (a) is the surface current distribution diagram at the fundamental mode f1 (0.954 THz) caused by electric dipole resonance; (b) is the surface current distribution diagram at the Q-BIC mode f2 (1.775 THz) caused by electric quadrupole resonance.

[0041] Fig. 9 It is a three-dimensional distribution diagram of the electric field intensity at two sensing resonance peak frequency points of the dual-mode terahertz reflective metasurface sensor prepared by the present invention (electric field under the excitation of TE wave at an incident angle of 45°).

[0042] Fig.10 This is a performance comparison diagram of the two sensing modes of the dual-mode terahertz reflective metasurface sensor prepared by the present invention with the traditional transmission-type terahertz metasurface and the traditional "metal-medium-metal" (MIM) type terahertz reflective metasurface sensor (based on the same THz superatom structure);

[0043] In the figure: 1--silicon substrate; 2--Cr / Ti adhesion layer; 3--metal reflective layer (first sputtering / evaporation); 4--patterned dielectric layer; 5--metal layer (second sputtering / evaporation); 6--incident terahertz wave; 7--reflected terahertz wave. DETAILED DESCRIPTION

[0044] The purpose of the present invention is to propose a method for preparing a high-sensitivity terahertz metasurface dual-mode sensor, discuss its sensitivity enhancement mechanism by analyzing its electromagnetic field and surface current distribution, prove its sensitivity enhancement effect and propose its preparation process. The present invention is described in detail below with reference to the accompanying drawings and examples.

[0045] The following examples are provided to further describe the present invention in detail. The examples are merely exemplary and are not intended to limit the sensor made according to the present invention to the materials, conditions or process parameters described herein.

[0046] The process flow of preparing a high-sensitivity dual-mode terahertz metasurface sensor according to a specific embodiment of the present invention is as follows: Figure 1 , Figure 2 shown.

[0047] Figure 1 The process uses polymer as the dielectric layer (PI as an example), and the specific steps include:

[0048] 1) Cleaning and drying: Clean the silicon wafer with acetone, isopropyl alcohol and water in sequence, and then dry it;

[0049] 2) Coating: Electron beam evaporation\magnetron sputtering to sequentially coat Ti\Cr film adhesion layer and metal reflective layer;

[0050] 3) Glue coating, glue leveling, and pre-baking: Spin-coat the photosensitive PI glue and pre-bake to prepare for the patterned dielectric layer structure;

[0051] 4) Photolithography and development inspection: UV exposure is performed after pre-baking, and then development and rinsing are performed with matching developer and cleaning solution to denature and pattern the photosensitive PI glue, and development inspection is performed;

[0052] 5) Imidization: Baking in a nitrogen environment (low oxygen environment) to remove residual solvents and photosensitive components in the photosensitive PI glue, enhance the adhesion of the dielectric layer, and convert the precursor into polyimide, which is the imidization process;

[0053] 6) Coating: Electron beam evaporation\magnetron sputtering is used to sequentially coat Ti\Cr film adhesion layer and metal layer. The plated metal layer is deposited on the patterned dielectric layer to form a terahertz metal microarray layer. At this point, the preparation of a high-sensitivity dual-mode terahertz metasurface is completed.

[0054] Figure 2The process flow shown uses oxide dielectric material as the dielectric layer (taking SiO2 as an example), and the specific steps include:

[0055] 1) Cleaning and drying: Clean the silicon wafer with acetone, isopropyl alcohol and water in sequence, and then dry it;

[0056] 2) Coating: electron beam evaporation\magnetron sputtering sequentially grows Ti\Cr film adhesion layer and metal reflective layer;

[0057] 3) Growth of dielectric layer: deposition of micron-sized oxide dielectric layer by chemical vapor deposition (PECVD) process;

[0058] 4) Glue coating, glue leveling, and pre-baking: substrate pretreatment, spin coating of photoresist, UV lithography, and development to prepare for patterned dielectric layer structure;

[0059] 5) Growth of hard mask layer: electron beam evaporation\magnetron sputtering to grow a hard mask of a certain thickness and remove excess photoresist;

[0060] 6) Etching: Dry-etch the dielectric layer until the metal layer is reached and the excess hard mask is released after the etching is completed;

[0061] 7) Coating: Ti\Cr film adhesion layer and metal layer are sequentially coated by electron beam evaporation\magnetron sputtering. The plated metal layer is deposited on the patterned dielectric layer to form a terahertz metal microarray layer. At this point, the high-sensitivity dual-mode terahertz metasurface based on weakened substrate sensitivity enhancement proposed in the present invention is completed.

[0062] The high-sensitivity terahertz metasurface dual-mode sensor prepared in the specific embodiment of the present invention is as follows Figure 3 As shown, from bottom to top it mainly includes: a base layer, a Cr / Ti adhesion layer, a metal reflective layer, a patterned PI dielectric layer, a Cr / Ti adhesion layer array, and a metal microstructure array layer. The metal reflective layer and the metal microarray layer are respectively fixed on the base layer and the patterned dielectric layer through the adhesion layer. The patterned PI dielectric layer is formed by photosensitive PI glue through MEMS processes such as photolithography, development and curing. The metal microstructure array layer is formed by directly depositing metal on the patterned dielectric layer.

[0063] In a specific embodiment of the present invention, the substrate material is silicon; the adhesion layer material is Cr / Ti; the metal reflective layer and the surface metal microstructure array adopt a conductivity of σ=4.56×10 7 The material of the patterned dielectric layer is polyimide (PI), and the thickness is h3 = 10 μm.

[0064] like Figure 4As shown, the high-sensitivity terahertz metasurface dual-mode sensor prepared in the specific embodiment of the present invention has a hollow square ring resonant unit structure with two perfect absorption peaks in two modes under the TE / TM terahertz wave oblique incidence excitation, and its size is outer length / width L=70μm, square ring line width w=5μm, and unit structure arrangement period P x =P y =70μm.

[0065] like Figure 5 As shown, when the sample solution to be tested is dripped onto the surface of the dual-mode terahertz metasurface sensor prepared in the specific embodiment of the present invention, on the one hand, the design of the patterned dielectric layer can accurately control the liquid thickness at the μm level, and reduce the absorption of THz waves by reducing the amount of liquid to be tested, thereby solving the testing problem caused by the strong absorption of THz waves by the polar liquid to be tested to a certain extent; on the other hand, the design of the patterned dielectric layer increases the volume of the overlapping area between the sample and the strong field energy, greatly enhancing the terahertz wave-matter interaction, which is conducive to achieving higher device sensitivity.

[0066] like Figure 6 As shown in the figure, the high-sensitivity terahertz metasurface dual-mode sensor (unloaded) prepared in the specific embodiment of the present invention will produce two perfect absorption peaks under the excitation of terahertz wave at 45° oblique incidence. Among them, mode 1 is located at low frequency (f1), which is a perfect absorption mode caused by the equivalent impedance matching of the top periodic structure with the free space and Fabry-Perot (FP) resonance; mode 2 is located at high frequency (f2), which is a bound state mode in the quasi-continuous domain (Q-BIC) caused by the phase asymmetry introduced by the incident angle. When the refractive index of the sample analyte loaded on the proposed terahertz metasurface changes, the resonance peaks of the two modes move significantly. According to the sensitivity calculation formula S = Δf / Δn and the quality factor calculation formula Q = f / FWHM, it can be calculated that under TE wave excitation, the sensitivities of mode 1 and mode 2 are 0.30THz / RIU and 0.53THz / RIU respectively; the quality factors are 36.3 and 75.9 respectively; under TM wave excitation, the sensitivities of mode 1 and mode 2 are 0.30THz / RIU and 0.57THz / RIU respectively; the quality factors are 34.6 and 80.8 respectively. In summary, the two resonance modes have high performance under TE / TM wave excitation.

[0067] like Figure 7As shown, the two modes of the terahertz dual-mode sensor prepared by the specific embodiment of the present invention have good angular robustness in TE / TM waves. Among them, the perfect absorption mode 1 caused by the top periodic structure matching the equivalent impedance of free space and the Fabry-Perot (FP) resonance maintains a large peak amplitude in the wide angle range of 0° to 70°; the peak amplitude of mode 2 is small under the normal incidence of the terahertz wave, and it is in the bound state mode (BIC) in the continuous domain with infinite Q value and unobservable amplitude. As the incident angle increases, the obliquely incident terahertz wave reaches the metasurface with a certain phase difference, and the asymmetry of the phase transforms the bound state mode (BIC) in the continuous domain into the bound state mode (Q-BIC) in the quasi-continuous domain with limited Q value and observable amplitude. The white dotted frame is the incident angle with a high signal-to-noise ratio of the current reflective terahertz spectrometer, that is, the two sensing modes of the proposed high-sensitivity terahertz dual-mode sensor based on weakened substrate sensitization have high measurability in actual measurement.

[0068] like Figure 8 As shown, the perfect absorption mode 1 caused by the equivalent impedance matching of the top periodic structure with the free space and the Fabry-Perot (FP) resonance is excited by the electric dipole; the bound state mode 2 (Q-BIC) in the quasi-continuous domain caused by the phase asymmetry introduced by the incident angle is excited by the electric quadrupole.

[0069] like Fig. 9 As shown in the electric field distribution stereogram, the strong field energy areas of the two modes of the terahertz metasurface sensor are mainly distributed inside and on the surface of the patterned dielectric layer, and the design of the patterned dielectric layer increases the interaction area between the sample to be tested and the strong field, laying the foundation for the high sensitivity of the device. At the same time, the field energy of mode 2 is stronger and more concentrated, which also explains Figure 4 Mode 2 has better sensing performance.

[0070] like Fig.10 As shown in the figure, based on the same terahertz metasurface unit structure, the two modes of the dual-mode terahertz metasurface sensor prepared by the present invention have obvious performance improvements compared with the traditional transmission metasurface sensor structure and the traditional MIM reflection metasurface sensor structure. The simulation results show that S 本发明模式2 ≈200%×S 本发明模式1 ≈360%×S 传统MIM反射型结构 ≈360%×S 传统透射型结构 This also fully demonstrates the sensitivity enhancement effect of the sensor structure proposed in the present invention and the high sensitivity sensing performance of the two modes of the designed sensor.

[0071] The above simulation demonstration is based on a graphic PI dielectric layer with a thickness of 10 μm and a dielectric constant of 3.5. If the dielectric constant of the dielectric layer is smaller, the sensitivity enhancement effect of the sensor structure proposed in the present invention will be more significant and the sensing performance will be more superior.

[0072] Although the embodiments of the present invention have been shown, they are not limited to those shown in the specification and the embodiments, and can be fully applied to various fields suitable for the present invention. It can be understood by those skilled in the art that various changes and improvements can be made to the embodiments without departing from the principles and purposes of the present invention, and these all belong to the protection scope of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a high-sensitivity terahertz metasurface dual-mode sensor, the steps comprising: 1) Clean the base layer, use acetone, isopropanol and water to clean it in sequence, then dry it, and then electron beam evaporate\magnetron sputter the adhesion layer and the metal reflective layer in sequence to form a substrate; 2) Patterning the dielectric layer using MEMS processing technology; the material of the patterned dielectric layer is an oxide dielectric material or a polymer dielectric material with a low dielectric constant, and the thickness is h3 = 1 μm to 20 μm; 3) Electron beam evaporation\magnetron sputtering is used to sequentially deposit an adhesion layer and a metal layer, and the metal layer is deposited on the patterned dielectric layer to form a terahertz metal microarray layer, thereby completing the preparation of a high-sensitivity dual-mode terahertz metasurface.

2. The method for preparing the high-sensitivity terahertz metasurface dual-mode sensor according to claim 1, characterized in that: The dielectric layer is made of polymer dielectric material, and step 2) specifically includes: 2-2) cleaning the substrate, sequentially washing with acetone, isopropanol and water, drying, and coating with a tackifier to increase the adhesion and stability of the photosensitive PI glue; 2-3) After the photosensitive PI glue is spin-coated on the substrate, it is pre-baked, then UV-lithography is performed, and it is rinsed with a developer and a cleaning solution in sequence to achieve patterning of the photosensitive PI glue; 2-4) The substrate in the above step is baked under a nitrogen environment to remove the residual solvent and photosensitive components in the photosensitive PI glue, enhance the adhesion of the dielectric layer, and realize the imidization of the precursor into polyimide.

3. The method for preparing the high-sensitivity terahertz metasurface dual-mode sensor according to claim 1, characterized in that: The dielectric layer is made of oxide dielectric material, and step 2) specifically includes: 2-5) depositing a micron-sized oxide dielectric layer by chemical vapor deposition (PECVD) process; 2-6) washing with acetone, ethanol and water in sequence, drying, and coating with a tackifier to increase the adhesion and stability of the photoresist; 2-7) Spin-coating photoresist, and performing UV photolithography and development; 2-8) Electron beam evaporation\magnetron sputtering to deposit a hard mask of a certain thickness; 2-9) removing excess photoresist and performing dry etching until the metal layer stops; 2-10) Release the excess hard mask.

4. The method for preparing the high-sensitivity terahertz metasurface dual-mode sensor according to claim 1, characterized in that: The substrate is a common substrate such as silicon or quartz, and has a thickness of h1 = 100 μm to 500 μm.

5. The method for preparing the high-sensitivity terahertz metasurface dual-mode sensor according to claim 1, characterized in that: The adhesion layer is made of Cr / Ti and has a thickness of about 5 to 10 nm.

6. The method for preparing the high-sensitivity terahertz metasurface dual-mode sensor according to claim 1, characterized in that: The metal reflective layer is a metal film of Au, Ag, Al or Cu with a thickness of h2=100nm-250nm.

7. The method for preparing the high-sensitivity terahertz metasurface dual-mode sensor according to claim 1, characterized in that: The terahertz metal microarray layer is made of Au, Ag, Al, and Cu, and has a thickness of h4=100 μm to 250 μm.

8. The method for preparing the high-sensitivity terahertz metasurface dual-mode sensor according to claim 7, characterized in that: The resonant unit in the terahertz metal microarray is in the shape of a hollow square ring, and its size is outer length / width L=20μm~100μm, square ring line width w=2μm~30μm, period P x =P y =40μm~200μm.

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