Substrate-etching based multi-band terahertz metamaterial sensor and method of use thereof

Abstract

The application discloses a multi-band terahertz metamaterial sensor based on substrate etching, which comprises a substrate and a resonance layer, the substrate comprises a bottom plate layer and an etching layer, the etching layer is formed on the bottom plate layer, the resonance layer is deposited on the etching layer, and the etching layer and the resonance layer form a patterned structure which comprises a first part in the shape of a long strip, a U-shaped second part and a U-shaped third part arranged in sequence along a center line, the opening of the second part faces the first part, and the opening of the third part faces the second part. The application further discloses a use method of the multi-band terahertz metamaterial sensor based on substrate etching. The application can characterize the same sample at different frequencies, realize multi-point matching of detection, and realize high-sensitivity detection of trace substances.

Description

Technical Field

[0001] This invention relates to the field of terahertz functional device technology. More specifically, this invention relates to a multi-band terahertz metamaterial sensor based on substrate etching and its application method. Background Technology

[0002] Electromagnetically induced transparency (EIT), first discovered in atomic systems, is a quantum interference effect that weakens the absorption of light by atoms at their resonant frequencies, allowing normally opaque media to produce a sharp, transparent window within a narrow spectral range. The EIT effect is typically accompanied by low loss and strong dispersion, making it promising for applications in optical storage and sensing. However, stringent experimental conditions, such as ultra-low operating temperatures, have long hindered the development of this technology.

[0003] In recent years, the emergence of metamaterials has enabled the EIT effect to be observed without extreme experimental conditions, and the flexible design of metamaterials has facilitated the formation of the EIT effect. Metamaterials are artificial materials with special structures, composed of subwavelength microstructural units, possessing unique properties not found in naturally occurring materials. By constructing different microstructural units, metamaterials can exhibit different characteristics, such as negative refraction and inverse Doppler effects. EIT-like metamaterials, characterized by strong field confinement, have attracted significant attention in the field of sensing. Improving the sensing performance of EIT-like metamaterials hinges on enhancing the interaction between terahertz waves and the detected substance, i.e., placing the substance at the location of the strongest electric field. Furthermore, in actual detection, different analytes may respond to the same resonance peak, making effective differentiation impossible. Therefore, designing multi-band and strongly interacting terahertz metamaterial sensors is of great significance. Summary of the Invention

[0004] This invention provides a multi-band terahertz metamaterial sensor based on substrate etching and its usage method, which can characterize the same sample at different frequencies, achieve multi-point matching for detection, and thus achieve highly sensitive detection of trace or minute substances.

[0005] To achieve these objectives and other advantages according to the present invention, a multi-band terahertz metamaterial sensor based on substrate etching is provided, comprising a substrate and a resonant layer. The substrate includes a base plate layer and an etched layer, wherein the etched layer is formed upward on the base plate layer, and the resonant layer is deposited upward on the etched layer. The etched layer and the resonant layer form a patterned structure comprising, sequentially arranged along a centerline, an elongated first portion, a U-shaped second portion, and a U-shaped third portion, wherein the opening of the second portion faces the first portion, and the opening of the third portion faces the second portion.

[0006] Preferably, the substrate is made of polytetrafluoroethylene and the resonant layer is made of gold.

[0007] Preferably, the thickness ratio of the base plate layer, the etched layer, and the resonant layer in the z-axis direction is 10:(8-12):(0.1-0.3).

[0008] Preferably, the width w of the first part, the second part, and the third part is equal, and the ratio of the width w to the x-axis length l1 of the first part, the y-axis length l2 of the second part, the x-axis length l3 of the second part, the x-axis length l4 of the third part, the y-axis length l5 of the third part, the distance h1 between the first part and the second part, and the distance h2 between the second part and the third part is 9:(88-92):(94-98):(88-92):(118-122):(20.5-24.5):(4-8):(4-8).

[0009] Preferably, the width w is proportional to the x-axis length P of the base plate layer. x The length P of the bottom plate layer in the y-axis direction y The ratio is 9:(130-134):(155-165).

[0010] The method of using the multi-band terahertz metamaterial sensor based on substrate etching includes:

[0011] Step 1: Cover the object to be tested onto the resonant layer;

[0012] Step 2: The terahertz wave is set as a periodic boundary condition in the x-axis and y-axis directions, and as an open boundary in the z-axis direction to simulate an infinite periodic array for electromagnetic excitation;

[0013] Step 3: Terahertz waves in the 0.3-1.5THz frequency band are incident perpendicularly on the test object. The electric and magnetic fields of the incident light are polarized along the x-axis and y-axis, respectively. The refractive index of the test object is calculated based on the resonant peak shift of the transmission spectrum of the test object.

[0014] Preferably, at 0.562 THz, the second part exhibits a bright mode and the third part exhibits a bright mode, coupling to generate an EIT electromagnetically induced transparent window.

[0015] Preferably, at 0.940 THz, the first part exhibits a bright mode and the third part exhibits a quasi-dark mode, which couples to generate an EIT electromagnetically induced transparent window.

[0016] Preferably, at 1.247 THz, the first part exhibits a quasi-dark mode and the second part exhibits a bright mode, coupling to generate an EIT electromagnetically induced transparent window.

[0017] Preferably, the coverage thickness of the analyte is 20-30µm.

[0018] The present invention has at least the following beneficial effects:

[0019] First, the multi-band terahertz EIT metamaterial sensor proposed in this invention was subjected to full-wave simulation calculation and parameter optimization using CST MWS 2020, which determined the optimal parameters and best performance of the structure.

[0020] Secondly, this invention enables the metamaterial sensor to exhibit three distinct transparent windows in the 0.3-1.5THz band of the transmission curve through near-field coupling between different modes. By optimizing the structural parameters, a refractive index sensitivity of up to 587GHz / RIU is obtained.

[0021] Third, the present invention conducted simulation tests on six different media, proving that the structure can effectively distinguish different substances and improve detection selectivity.

[0022] Fourth, the method of etching the substrate to improve sensitivity, as described in this invention, is not easily conceived. Currently, most metamaterial designs focus on how to excite different resonant modes to improve performance. Therefore, during the design process, only the shape of the resonant layer is considered, neglecting the portion of the electric field penetrating into the substrate. This means that light and matter do not interact sufficiently, resulting in limited performance. Compared to the structure without substrate etching, the refractive index sensitivity is improved. Taking the structure in this invention as an example, after substrate etching, the refractive index sensitivity of the third EIT window increases from 370 GHz / RIU to 587 GHz / RIU, which is 1.58 times that of the unetched structure.

[0023] Fifth, the metamaterial sensor proposed in this invention has a simple structure and is easy to manufacture. The substrate etching method enables the sensor to achieve a high level of sensitivity. The proposed sensor has three EIT transmission peaks, which effectively reduces errors caused by interference during detection in a single frequency band. It achieves multi-point feature matching, allowing the same sample to be characterized at different frequencies, thereby improving detection selectivity. This design method has not yet been used in the field of terahertz detection.

[0024] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the multi-band terahertz EIT metamaterial sensor of the present invention;

[0026] Figure 2 This is the transmission spectrum of the sensor of the present invention when there is no object to be measured.

[0027] Figure 3 The transmission spectra of the first part CL, the second part UR, and the third part MB of this invention;

[0028] Figure 4 This is a diagram showing the electric field distribution of the four troughs and three EIT transmission peaks of the present invention.

[0029] Figure 5 The thickness of the sensor in this invention affects its sensitivity when covered by the object to be measured.

[0030] Figure 6 The effect of the etching layer thickness on the sensitivity of the sensor of the present invention;

[0031] Figure 7 This is a two-dimensional electric field distribution diagram of the xy plane of the sensor of the present invention with different etched layer thicknesses at f3=1.247THz;

[0032] Figure 8 The transmission curves of this invention are shown in media with different refractive indices. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0034] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0035] It should be noted that, unless otherwise specified, the experimental methods described in the following embodiments are conventional methods, and the reagents and materials mentioned are commercially available. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "setting" should be interpreted broadly. For example, they can refer to fixed connection or setting, detachable connection or setting, or integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The terms "lateral," "longitudinal," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description. They 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, and therefore should not be construed as a limitation of this invention.

[0036] like Figure 1As shown, this invention provides a multi-band terahertz metamaterial sensor based on substrate etching, comprising a substrate and a resonant layer. The substrate includes a base layer and an etched layer. The base layer is a single piece of polytetrafluoroethylene (PTFE). The etched layer is formed upward on the base layer and is a patterned PTFE structure. The PTFE has a dielectric constant ε = 2.1 and a dielectric loss tangent of 0.002. The resonant layer is deposited upward on the etched layer. The resonant layer is made of gold and has a conductivity σ (4.561 × 10⁻⁶). 7 The S / m is composed of patterned metal periodically deposited on a substrate (etched layer). The etched layer and the resonant layer form a patterned structure, which includes a first part in the shape of an elongated strip, a second part in the shape of a U-shape, and a third part in the shape of a U-shape arranged in sequence along the center line. These are referred to as CL, UR, and MB, respectively, in the following text. The opening of the second part faces the first part, and the opening of the third part faces the second part.

[0037] In another technical solution, the z-axis thickness ratio of the base plate layer, the etching layer, and the resonant layer is d1, d2, d3 = 10:(8-12):(0.1-0.3), preferably 10:10:0.2. The width w of the first, second, and third portions is equal, and its ratio to the x-axis length l1 of the first portion, the y-axis length l2 of the second portion, the x-axis length l3 of the second portion, the x-axis length l4 of the third portion, the y-axis length l5 of the third portion, the distance h1 between the first and second portions, and the distance h2 between the second and third portions is 9:(88-92):(94-98):(88-92):(118-122):(20.5-24.5):(4-8):(4-8), preferably 9:90:96:90:120:22.5:6:6. The width w and the x-axis length P of the base plate layer... x The length P of the bottom plate layer in the y-axis direction y The ratio is 9:(130-134):(155-165), preferably 9:132:160. In a preferred embodiment, the structural optimization parameters are shown in Table 1.

[0038] Table 1

[0039]

[0040] This invention employs the three-dimensional electromagnetic field simulation software CST MWS 2020 to model and simulate the metamaterial sensor structure. A frequency domain solver based on the finite integral method (FIT) is used to calculate the sensor's transmission characteristic curve, electric field distribution, and other parameters. Furthermore, periodic boundary conditions are set in the x and y axes, while an open boundary is set in the z-axis direction to simulate an infinite periodic array. Terahertz waves are incident perpendicularly to the upper surface of the sensor, with polarization along the x-axis; that is, the electric and magnetic fields of the incident light are polarized along the x and y axes, respectively. The transmission spectrum of the sensor without analyte coverage is shown below. Figure 2 As shown in the figure, the designed sensor has three EIT transmission peaks at f1=0.562THz, f2=0.940THz and f3=1.247THz.

[0041] To further explore the formation mechanism of the multi-band EIT effect, the three substructures were analyzed separately. Under the same polarization conditions, CL and MB resonated at 1.192 THz and 0.754 THz, respectively, while UR resonated at 0.475 THz and 1.286 THz. The transmission spectra of the three substructures are as follows: Figure 3 As shown.

[0042] There are generally three methods for achieving EIT-like effects based on metamaterials: one is the destructive coupling between bright and dark modes; another is the weak hybrid coupling between bright modes; and the last is the near-field coupling and destructive interference between bright and quasi-dark modes. Bright modes refer to strong resonant modes that can be directly excited by incident light, quasi-dark modes refer to resonant modes that can be excited by incident light but have a lower resonance peak quality factor than bright modes, and dark modes refer to weak resonant modes indirectly excited by bright modes.

[0043] For the first EIT transparent window, both UR and MB can be directly excited by the incident wave at low frequencies, and are therefore defined as bright modes. UR produces a strong resonance centered at 0.475 THz, with a Q factor of 5.56. Figure 3 As shown in (a), MB exhibits a strong resonance at 0.754 THz with a Q factor of 4.2, as... Figure 3 As shown in (b), the resonant frequencies of the two substructures are close and their Q factors are not significantly different. Strong near-field coupling and weak hybridization occur between the two bright modes, resulting in a distinct EIT transparency window at f1 = 0.562 THz.

[0044] For the second EIT transparent window, although both MB and CL, as two substructures, can directly couple with the incident wave and exhibit strong resonance, such as Figure 3As shown in (c). However, the Q factor of the resonance peak generated by CL is 11.4, which is significantly different from the Q factor of the resonance peak generated by MB. Therefore, CL is defined as the bright mode and MB is defined as the quasi-dark mode. The two undergo near-field coupling and interference cancellation, thus forming a second EIT transparent window at f2=0.940THz.

[0045] The third EIT transparency window is generated by the interference between the resonance peak of UR at high frequency and the resonance peak generated by CL. The Q factor of the resonance peak of UR at high frequency is 28.5, which is significantly different from the Q factor of CL. Therefore, the two are coupled as bright mode and quasi-dark mode respectively, generating the third EIT transparency window at f3=1.247THz.

[0046] To further explain the EIT effect generation mechanism of the present invention, such as Figure 4 As shown, Figure 4 (a) shows the electric field distribution at the four trough frequencies. Figure 4 (b) shows the electric fields at three transmission peak frequencies. At 0.475 THz, the three structures are excited by the incident terahertz wave, generating electric fields of different intensities. At this point, the electric field intensity generated by UR is the highest, resulting in LC resonance. At 0.754 THz, the electric field of MB plays a major role in the structure, and the electric field is mainly distributed at both ends of MB, exhibiting dipole resonance. Similarly, at 1.192 THz, the electric field of the CL structure is mainly located at both ends, also exhibiting dipole resonance. At 1.192 THz, the electric field at the four corners of UR is highly concentrated, with a large number of opposite charges accumulating at the two left corners, which are opposite to those on the right, exhibiting quadrupole resonance. At the first EIT transmission peak frequency f1 = 0.562 THz, the weak hybridization between the bright modes that play a major role at two adjacent trough frequencies significantly weakens the electric field intensity, thus forming an EIT transparent window. At the second and third EIT transparent windows, the weakening of the electric field at the transparent window is also due to the destructive interference of the bright and dark modes at adjacent trough frequencies, resulting in the EIT effect.

[0047] The application methods of multi-band terahertz metamaterial sensors based on substrate etching include:

[0048] Step 1: Cover the object to be tested onto the resonant layer;

[0049] Step 2: The terahertz wave is set as a periodic boundary condition in the x-axis and y-axis directions, and as an open boundary in the z-axis direction to simulate an infinite periodic array for electromagnetic excitation;

[0050] Step 3: Terahertz waves in the 0.3-1.5THz frequency band are incident perpendicularly on the test object. The electric and magnetic fields of the incident light are polarized along the x-axis and y-axis, respectively. The refractive index of the test object is calculated based on the resonant peak shift of the transmission spectrum of the test object.

[0051] At f1=0.562THz, the second part exhibits a bright mode, the third part exhibits a bright mode, and the coupling generates an EIT electromagnetically induced transparent window.

[0052] At f2 = 0.940 THz, the first part exhibits a bright mode, and the third part exhibits a quasi-dark mode, which couples to produce an EIT electromagnetically induced transparent window.

[0053] At f3 = 1.247 THz, the first part exhibits a quasi-dark mode, and the second part exhibits a bright mode, which couples to produce an EIT electromagnetically induced transparency window.

[0054] Experiment (I) The effect of the thickness of the test object on multi-frequency EIT resonance:

[0055] The thickness and dielectric constant of the analyte on the sensor surface affect the frequency shift and intensity of the absorption characteristic curve. Based on the detection principle of metamaterial sensors, the relationship between the frequency shift and the resonant frequency is derived from Maxwell's equations as follows:

[0056]

[0057] Where ω p0 Let E0 and H0 be the resonant frequency when the analyte is not covered, E0 and H0 be the initial field quantities, ΔV be the change in volume of the analyte, and Δε and Δμ be the changes in dielectric constant and permeability, respectively. Changes in the analyte will cause changes in Δε and Δμ, resulting in different degrees of frequency shift, ultimately enabling the detection of the analyte. Changes in the volume of the analyte on the sensor surface will cause different frequency shifts for the same analyte; a larger frequency shift indicates higher sensitivity. Since thickness causes changes in volume, the thickness of the analyte will affect the sensor's sensitivity.

[0058] To determine the optimal thickness, simulations were performed by covering the sensor surface with test materials of varying thicknesses and refractive indices n=1.3-1.8. The sensitivity obtained through fitting was as follows: Figure 5 As shown. Figure 5 (a) is the fitting sensitivity of f1=0.562THz when the test object is covered with different thicknesses. Figure 5 (b) The fitting sensitivity of f2=0.940THz when the test object is covered with different thicknesses; Figure 5 (c) shows the fitted sensitivity of f3=1.247THz when the analyte is covered with different thicknesses. It can be found that the sensitivity of the three EIT windows increases to varying degrees with the increase of the thickness, but the growth rate tends to level off after the thickness of the analyte exceeds 30µm. Figure 5(d) shows the effect of the thickness of the analyte on the sensitivity. This is because the incident wave excites the current on the sensor surface to oscillate, and the greater the distance, the faster the oscillation decays. In other words, the sensor sensitivity remains almost unchanged after the thickness exceeds 30µm. To obtain the best sensing effect of the multi-band EIT sensor, the subsequent discussion will choose a thickness of 30µm.

[0059] Experiment (II) The effect of etching layer thickness on multi-frequency EIT resonance:

[0060] The thickness of the etched layer in the sensor affects the multi-frequency EIT resonance. Simulations were performed with etched layer thicknesses of 0, 2, 4, 6, 8, and 10 μm. Different degrees of blue shift were observed in the three EIT-like windows under different etched layer thicknesses. This is due to the gradual decrease in the effective dielectric constant near the metamaterial. UR, excited by the incident wave, exhibits LC resonance, and its resonance frequency strongly depends on the dielectric constant of the electric field-excited hotspot. MB and CL, excited by the incident wave, exhibit dipole resonance, with resonance frequencies of [missing information]. , where ε eff The effective dielectric constant of the surrounding medium is ε. Therefore, as the etching thickness increases, the ε around the metamaterial increases. eff This will significantly reduce the sensitivity, resulting in a blue shift in the EIT resonance. To investigate the effect of etching layer thickness on the sensing performance of multi-frequency EIT metamaterials, analytes with refractive indices n=1.3-1.8 were coated onto the sensor surface and within the trenches at different etching layer thicknesses. The sensitivity obtained through fitting was as follows: Figure 6 As shown. Figure 6 (a) is the fitting sensitivity of f1=0.562THz for different etched layer thicknesses. Figure 6 (b) is the fitting sensitivity of f2=0.940THz for different etched layer thicknesses; Figure 6 (c) shows the fitting sensitivity for f3=1.247THz at different etched layer thicknesses. It can be clearly seen that as the etched layer thickness increases from 0 to 10µm, the slope of the fitting line also gradually increases. The sensitivities of the three windows increase from 173GHz / RIU, 283GHz / RIU, and 370GHz / RIU to 284GHz / RIU, 477GHz / RIU, and 587GHz / RIU, respectively. However, the rate of increase begins to decrease after 2µm. Figure 6 (d) shows the effect of etching layer thickness on sensitivity. Etching can improve the sensing sensitivity of multi-frequency EIT metamaterials, but the improvement rate will be slowed down.

[0061] To analyze the impact of substrate etching on sensitivity, a two-dimensional electric field distribution diagram of the xy plane of this invention was plotted sequentially downwards from the sensor surface with a step size of 2µm, as shown below. Figure 7As shown, taking f3=1.247THz as an example, an electric field was found on different planes, indicating that a portion of the electric field generated by the resonant layer penetrates into the substrate, and this portion of the electric field is not utilized during sensing. Etching can maximize the utilization of this portion of the electric field, ensuring full overlap between the electric field and the material being detected, guaranteeing interaction between the strong light and the material, and thus improving the sensor's ability to detect the material. Simultaneously, it can be observed that the electric field significantly decreases with increasing etch layer thickness, manifesting as a slower and more stable rate of increase in sensor sensitivity with increasing etch layer thickness. Therefore, proper etching of the substrate can effectively improve the sensitivity of metamaterial sensors.

[0062] To verify the practical application effect of this application as a biosensor, simulation tests were conducted on different media with refractive indices ranging from 1.333 to 1.5012, including water (n=1.333), ethanol (n=1.357), pentanol (n=1.401), carbon tetrachloride (n=1.453), glycerol (n=1.473), and benzene (n=1.5012). The media selected for testing have wide applications in the medical and biochemical fields. Figure 8 As shown, all three EIT transparent windows can distinguish six different media. With the increase of refractive index, all three EIT windows undergo redshift, with the f3 frequency shift being more obvious compared to f1 and f2.

[0063] To further verify that this application can achieve multi-point feature matching in different frequency bands, the refractive indices n(f1), n(f2), and n(f3) of each medium under different EIT windows were calculated based on the resonance peak shift of the transmission spectrum of each medium, and compared with its standard refractive index n ref Compare them.

[0064] n medium =1+Δn=1+Δf / (S(f))

[0065] Where Δf is the frequency shift of the EIT transparency window caused by the addition of the analyte, and Δn is the frequency shift relative to n. air The refractive index change S(f) = 1 represents the refractive index sensitivity at that frequency. Table 2 shows the simulation and calculation results of the test objects covered by this invention. As can be seen from Table 2, the refractive indices n(f1), n(f2), and n(f3) of the test objects are similar and close to the standard value n. ref Taking water as an example, the calculated refractive indices in modes f1, f2, and f3 are 1.351, 1.35, and 1.348, respectively, with a standard refractive index of 1.333. By comparing the peak frequencies of the three EIT windows, more accurate substance detection can be achieved in practical sensing applications, effectively reducing errors caused by interference in a single frequency band during detection. In summary, this invention can be used as a highly sensitive sensor for substance detection.

[0066] Table 2

[0067]

[0068] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention. Applications, modifications, and variations of the invention will be readily apparent to those skilled in the art.

[0069] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A multi-band terahertz metamaterial sensor based on substrate etching, characterized in that, The device includes a substrate and a resonant layer. The substrate includes a base plate layer and an etched layer. The etched layer is formed upward on the base plate layer, and the resonant layer is deposited upward on the etched layer. The etched layer and the resonant layer form a patterned structure, which includes: a first elongated portion, a second U-shaped portion, and a third U-shaped portion arranged sequentially along the same center line. The opening of the second portion faces the first portion, and the opening of the third portion faces the second portion. The width w of the first part, the second part, and the third part is equal, and the ratio of the width w to the x-axis length l1 of the first part, the y-axis length l2 of the second part, the x-axis length l3 of the second part, the x-axis length l4 of the third part, the y-axis length l5 of the third part, the distance h1 between the first part and the second part, and the distance h2 between the second part and the third part is 9:(88-92):(94-98):(88-92):(118-122):(20.5-24.5):(4-8):(4-8).

2. The substrate-etching-based multi-band terahertz metamaterial sensor of claim 1, wherein, The substrate is made of polytetrafluoroethylene, and the resonant layer is made of gold.

3. The substrate-etching-based multi-band terahertz metamaterial sensor of claim 1, wherein, The thickness ratio of the base plate layer, the etched layer, and the resonant layer in the z-axis direction is 10:(8-12):(0.1-0.3).

4. The substrate-etching-based multi-band terahertz metamaterial sensor of claim 1, wherein, The width w and the x-axis length P of the base plate layer x The length P of the bottom plate layer in the y-axis direction y The ratio is 9:(130-134):(155-165).

5. The method of using the multi-band terahertz metamaterial sensor based on substrate etching as described in any one of claims 1-4, characterized in that, include: Step 1: Cover the object to be tested onto the resonant layer; Step 2: The terahertz wave is set as a periodic boundary condition in the x-axis and y-axis directions, and as an open boundary in the z-axis direction to simulate an infinite periodic array for electromagnetic excitation; Step 3: Terahertz waves in the 0.3-1.5THz frequency band are incident perpendicularly on the test object. The electric and magnetic fields of the incident light are polarized along the x-axis and y-axis, respectively. The refractive index of the test object is calculated based on the resonant peak shift of the transmission spectrum of the test object.

6. The method of using a substrate-etching based multi-band terahertz metamaterial sensor of claim 5, wherein, At 0.562 THz, the second part exhibits a bright mode, and the third part exhibits a bright mode, with coupling generating an EIT electromagnetically induced transparent window.

7. The method of claim 5, wherein the substrate-etching-based multi-band terahertz metamaterial sensor is used for, At 0.940 THz, the first part exhibits a bright mode, and the third part exhibits a quasi-dark mode, which couples to produce an EIT electromagnetically induced transparency window.

8. The method of using the multi-band terahertz metamaterial sensor based on substrate etching as described in claim 5, characterized in that, At 1.247 THz, the first part exhibits a quasi-dark mode, and the second part exhibits a bright mode, with coupling generating an EIT electromagnetically induced transparency window.

9. The method of using the multi-band terahertz metamaterial sensor based on substrate etching as described in claim 5, characterized in that, The coverage thickness of the sample is 20-30µm.

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