Tetramer metasurface sensor

Abstract

The invention provides a tetramer metasurface sensor which comprises a tetramer metasurface composed of a plurality of tetramer metasurface units arranged periodically, a signal generator and a spectrograph, and each tetramer metasurface unit comprises a nanometer substrate, two first elliptic cylinder nanometer discs and two second elliptic cylinder nanometer discs; when the semi-major axes of the first elliptic cylinder nanodisk and the second elliptic cylinder nanodisk are different in size and the tetramer metasurface is irradiated, the refractive index of the biological sample to be detected is calculated through resonant wavelengths of three formed quasi-BIC resonant modes, so that the detection range of the biological sample can be widened; when the semi-major axes of the first elliptic cylinder nano-disc and the second elliptic cylinder nano-disc are equal in size, and the tetramer metasurface immersed in the biological sample to be detected and the bare nano-substrate are scanned respectively, the absorption enhancement factor of the metasurface is calculated through the absorption spectrum, and then the extinction coefficient of the biological sample to be detected can be determined. The accuracy of biological sample type detection is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of micro-nano optical technology and relates to a sensor, in particular to a tetramer supersurface sensor, which can be used in technical fields such as biological sample detection. Technical Background

[0002] A sensor is a detection device that can sense the information of the detected physical quantity and convert it into an electrical signal or other required form of information output according to a certain rule to meet the requirements of information transmission, processing, display, etc. The sensor is mainly composed of a sensitive element and a conversion element. The sensitive element is responsible for directly sensing the detected physical quantity and outputting the physical quantity information that has a definite relationship with the measured quantity. It is the most important component of the sensor. Sensors can be divided into electromechanical sensors, photoelectric sensors, thermoelectric sensors, and electrochemical sensors according to the principle of conversion of physical quantity information. Metasurface sensors are a typical photoelectric sensor, including a metasurface with periodic units arranged to manipulate the propagation and interaction of electromagnetic waves as a sensitive element, a signal generator to excite electromagnetic waves, and a spectrometer to process and display the detected physical quantity information in the scattered electromagnetic waves as a conversion element.

[0003] By optimizing the structure of the metasurface unit, the detection accuracy and range of the metasurface sensor can be improved. The typical method is to design a unit structure that satisfies both axial symmetry and central symmetry, and realize the infinite Q value of the metasurface continuum bound state BIC (Bound states in the continuum). Then, by perturbing the symmetry of the unit or the structural spacing, the BIC is transformed into a quasi-BIC that can transmit physical quantity information. At this time, the Q value of the electromagnetic wave resonance mode received by the spectrometer can reach 10 of that of other structures. 2 -10 3 times.

[0004] Different biological samples have different refractive indices and extinction coefficients. The refractive index affects the wavelength and propagation path of electromagnetic waves, while the extinction coefficient affects the absorption response of electromagnetic waves. Taking the refractive index of pure water as 1.3, the refractive index of gaseous and liquid biological samples is less than and greater than 1.3, respectively. When testing biological samples, the refractive index can be used to determine the category of the biological sample to be tested. However, if different types of the same category need to be tested, it is often necessary to use the extinction coefficient of the biological sample to be tested.

[0005] The tetramer metasurface unit includes a nanosubstrate and four uniform cylindrical or prismatic nanodisks deposited on its upper surface. When electromagnetic waves irradiate the biological sample to be tested immersed in the metasurface, the electromagnetic wave resonance mode received by the spectrometer has high sensitivity, which can achieve accurate detection of the category of the biological sample to be tested. For example, Xueer Chen, YongZhang, Guoxiong Cai et al. published an article entitled "All-dielectric metasurfaces with high Q-factor Fano resonances enablingmulti-scenario sensing" in the journal Nanophotonics, Volume 11, Issue 20, Pages 4537-4549 in 2023, disclosing a tetramer metasurface sensor, which uses a periodic metasurface unit of a SiO2 nanosubstrate with tetramer tetrahedral silicon nanodisks deposited on the upper surface as a sensitive element, wherein the relative tetrahedral silicon nanodisks have the same size, and the adjacent tetrahedral silicon nanodisks have different sizes. When the biological sample to be tested is immersed above the metasurface and the applied x-polarized electromagnetic wave is applied to vertically irradiate the metasurface, three independent quasi-BIC resonance modes are observed through spectrometer processing, and the calculation of the resonance wavelength proves that the sensor can achieve accurate detection of biological samples with a refractive index range of 1.3-1.5. However, since the four quadrangular prism silicon nanodisks used in the invention have a uniform structure, the applicable biological sample detection range is narrow and cannot cover the detection of biological samples within a wider refractive index range. In addition, the invention only considers the refractive index information of the biological sample and ignores the extinction coefficient information, and cannot achieve accurate discrimination of the type of biological sample. Summary of the invention

[0006] The purpose of the present invention is to address the problems existing in the prior art and propose a tetramer metasurface sensor, aiming to broaden the detection range of biological sample detection and improve the accuracy of biological sample type detection.

[0007] To achieve the above-mentioned purpose, the present invention comprises a tetramer metasurface composed of L×M periodically arranged tetramer metasurface units, a signal generator and a spectrometer for exciting x-polarized electromagnetic waves, L≥2, M≥2; the tetramer metasurface unit comprises a nanosubstrate 1 with a square cross-section and four cylindrical nanodisks deposited on its upper surface and uniformly distributed on the same virtual circle; the four cylindrical nanodisks are composed of two adjacent first elliptical cylindrical nanodisks 2 with two long semi-axes R1 parallel to the x-axis polarization direction and two adjacent second elliptical cylindrical nanodisks 3 with two long semi-axes R2 parallel to the x-axis polarization direction; the biological sample to be tested is immersed in the upper surface of the tetramer metasurface;

[0008] When R1≠R2, and the wavelength of the x-polarized electromagnetic wave is λ1, and the radius of the virtual circle where the four elliptical cylindrical nanodisks are located is D1, the x-polarized electromagnetic wave irradiates the tetramer metasurface vertically from top to bottom, and the spectrometer calculates the refractive index n of the biological sample to be tested by receiving the resonant wavelengths of the three quasi-BIC resonant modes formed by the tetramer metasurface;

[0009] When R1=R2, and the wavelength of the x-polarized electromagnetic wave is λ2, the radius of the virtual circle where the four elliptical cylindrical nanodisks are located is D2, D1>D2, λ1>λ2, the x-polarized electromagnetic wave is scanned from top to bottom along the normal-tangential path of the tetramer metasurface to the tetramer metasurface immersed in the biological sample to be tested and the bare nanosubstrate of the same size, respectively. The spectrometer receives the absorption rate spectrum A in the broadband absorption response of the metasurface and the bare nanosubstrate. m , A s The calculated absorption enhancement factor χ of the metasurface is used to determine the extinction coefficient of the biological sample to be tested.

[0010] The above-mentioned metasurface sensor, the resonant wavelengths of the three resonant modes formed by the tetramer metasurface, wherein the three resonant modes respectively refer to the resonant mode formed by the two first elliptical cylindrical nanodisks 2 and the two second elliptical cylindrical nanodisks 3, the resonant mode formed by the semi-major axis dimensions of the four elliptical cylindrical nanodisks, and the resonant mode formed by the four elliptical cylindrical nanodisks on the virtual circle; wherein the resonant wavelength refers to the wavelength value at which the three resonant modes undergo quasi-BIC resonance within the wavelength λ1 range of the x-polarized electromagnetic wave.

[0011] In the above-mentioned super-surface sensor, the nano-substrate 1 and the bare nano-substrate are both made of SiO2.

[0012] In the above-mentioned supersurface sensor, the center of the virtual circle where the four columnar nanodisks distributed on the nanosubstrate 1 are located is located on the center normal line of the nanosubstrate 1 .

[0013] In the above-mentioned metasurface sensor, the two first elliptical cylindrical nanodisks 2 and the two second elliptical cylindrical nanodisks 3 are respectively located on two diagonal lines on the upper surface of the nanosubstrate 1 .

[0014] In the above-mentioned metasurface sensor, the long axes of the two first elliptical cylindrical nanodisks 2 and the two second elliptical cylindrical nanodisks 3 coincide with the two diagonals of the upper surface of the nanosubstrate 1 on which they are located.

[0015] For the above-mentioned metasurface sensor, the refractive index n of the biological sample to be tested is calculated as follows:

[0016]

[0017] in, They represent the resonant wavelength and reference wavelength of the i-th resonant mode when the wavelength of the x-polarized electromagnetic wave is λ1, i∈[1,2,3], S i represents the sensitivity of the i-th resonance mode.

[0018] For the above-mentioned metasurface sensor, the absorption enhancement factor χ is calculated as follows:

[0019]

[0020] in, They respectively represent the lower limit and upper limit of the wavelength λ2 of the x-polarized electromagnetic wave, and dλ2 represents the differential operation on λ2.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. Among the four elliptical cylindrical nanodisks included in the tetramer metasurface unit of the present invention, when the long semi-axis sizes of the first elliptical cylindrical nanodisk and the second elliptical cylindrical nanodisk are not equal, and the x-polarized electromagnetic wave irradiates the metasurface vertically from top to bottom, the tetramer metasurface will form three quasi-BIC resonance modes. The resonance wavelengths of the three resonance modes at the edges of the four elliptical cylindrical nanodisks close to the center of the virtual circle will gather more induced charges, which significantly promotes the interaction between the tetramer metasurface and the immersed biological sample, thereby improving the detection range of biological sample detection.

[0023] 2. In the present invention, when the long semi-axis sizes of the first elliptical cylindrical nanodisk and the second elliptical cylindrical nanodisk are equal, when the x-polarized electromagnetic wave scans the tetramer metasurface and the bare nanosubstrate immersed in the biological sample to be tested from top to bottom, the tetramer metasurface will form a quasi-BIC resonance mode. At the resonance wavelength, the biological sample to be tested interacts with the induced charges on the four elliptical cylindrical nanodisks, which significantly enhances the absorption spectrum of the metasurface. The absorption enhancement factor of the metasurface is calculated through the absorption spectra of the tetramer metasurface and the bare nanosubstrate, and the extinction coefficient of the biological sample to be tested can be determined, thereby avoiding the defect of the prior art that the extinction coefficient information is ignored, and effectively improving the accuracy of biological sample type detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the overall structure of Embodiment 1 of the present invention;

[0025] Figure 2 is a schematic structural diagram of a tetramer supersurface unit in Example 1 of the present invention;

[0026] Figure 3 is a schematic structural diagram of a tetramer supersurface unit in Example 2 of the present invention;

[0027] Figure 4is a simulation comparison diagram of three quasi-BIC resonance modes and Fano fitting in Example 1 of the present invention;

[0028] Figure 5 1 is a simulation diagram of electric field distribution at reference wavelengths of three quasi-BIC resonance modes in Example 1 of the present invention;

[0029] Figure 6 is a simulation diagram of the sensitivity of three quasi-BIC resonance modes in Example 1 of the present invention;

[0030] Figure 7 This is a simulation diagram of the change of the resonance mode when the electromagnetic wave scans the tetramer metasurface in Example 2 of the present invention.

[0031] Figure 8 It is a simulation diagram of the absorption enhancement factor χ of the tetramer metasurface with biological samples to be tested having different extinction coefficients immersed on the upper surface in Example 2 of the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0033] Reference Figure 1 The present invention includes a tetramer metasurface composed of L×M periodically arranged tetramer metasurface units, a signal generator and a spectrometer for exciting x-polarized electromagnetic waves, L≥2, M≥2, and an embodiment L=3, M=3.

[0034] The tetramer super surface unit includes a nano substrate 1 with a square cross section and a side length of 1600nm, and four columnar nano disks deposited on its upper surface and distributed on the same virtual circle, and the height of the nano disks is 220nm. The four columnar nano disks are composed of two adjacent first elliptical column nano disks 2 with two long semi-axes R1 and short semi-axes 100nm parallel to the polarization direction of the x-axis and two adjacent second elliptical column nano disks 3 with two long semi-axes R2 and short semi-axes 100nm parallel to the polarization direction of the x-axis. The nano substrate 1 is made of SiO2 material, and the two first elliptical column nano disks 2 and the two second elliptical column nano disks 3 are all made of Si material. The center of the virtual circle where the four columnar nano disks are distributed on the nano substrate 1 is located on the center normal of the nano substrate 1. The two first elliptical column nano disks 2 and the two second elliptical column nano disks 3 are respectively located on the two diagonals on the upper surface of the nano substrate 1, and their long axes coincide with the two diagonals on the upper surface of the nano substrate 1 where they are located. The biological sample to be tested is immersed in the tetramer metasurface sensor, and an optical three-dimensional surface profiler is used to ensure that the height of the biological sample to be tested immersed in the metasurface is consistent everywhere.

[0035] The tetramer metasurface is located on the Xoy plane in the three-dimensional coordinate system, and its upper surface points to the z-axis direction of the three-dimensional coordinate system. The x-polarization direction of the electromagnetic wave is the same as the x-axis direction of the three-dimensional coordinate system.

[0036] Embodiment 1:

[0037] Reference Figure 2 In this embodiment, R1≠R2, wherein R1=150nm, R2=140nm, the wavelength of the x-polarized electromagnetic wave is λ1, the radius of the virtual circle where the four columnar nanodisks are located is D1=760nm, the applied x-polarized electromagnetic wave irradiates the metasurface vertically, and the height of the biological sample to be tested is 250nm.

[0038] The spectrometer calculates the refractive index n of the biological sample to be tested by receiving the resonant wavelengths of the three quasi-BIC resonant modes formed by the tetramer metasurface, wherein the three resonant modes formed by the tetramer metasurface are independent of each other, namely the resonant mode formed by the two first elliptical cylindrical nanodisks 2 and the two second elliptical cylindrical nanodisks 3, the resonant mode formed by the semi-major axis size of the four elliptical cylindrical nanodisks, and the resonant mode formed by the four elliptical cylindrical nanodisks on the virtual circle, and the resonant wavelength refers to the wavelength value of the three resonant modes that respectively undergo quasi-BIC resonance within the wavelength λ1 range of the x-polarized electromagnetic wave. At the same time, the calculation formula of n is:

[0039]

[0040] in, They represent the resonant wavelength and reference wavelength of the i-th resonant mode when the wavelength of the x-polarized electromagnetic wave is λ1, respectively. i Represents the sensitivity of the i-th resonance mode, i∈[1,2,3]. The reference wavelength and sensitivity of each resonance mode are fixed values ​​and need to be determined through simulation.

[0041] The working principle of this embodiment is: when the x-polarized electromagnetic wave irradiates the tetramer metasurface vertically, the spectrometer receives the resonance wavelengths of three quasi-BIC resonance modes within the wavelength range of λ1, and calculates the refractive index n of the biological sample through the reference wavelength and sensitivity of the resonance mode. Compared with the tetramer structure using regular prism or cylindrical nanodisks to form a metasurface unit, the tetramer structure of the metasurface unit is formed by aligning the long axes of the two first elliptical nanodisks 2 and the two second elliptical nanodisks 3 with the two diagonals of the upper surface of the nanosubstrate 1 where they are located, and the edges of the four elliptical nanodisks close to the center of the virtual circle will gather more induced charges under the irradiation of electromagnetic waves, and significantly promote the interaction between the biological sample immersed on the upper surface of the metasurface and the metasurface at the resonance wavelength, thereby improving the detection range of biological sample detection.

[0042] Embodiment 2:

[0043] Reference Figure 3 The basic structure of this embodiment is the same as that of Embodiment 1, and only some parameters and the incident mode of the incident wave are adjusted, specifically: R1=R2=150nm, and the x-polarized electromagnetic wave with a wavelength of λ2 is scanned along the normal-tangential path of the quadruplex metasurface to the metasurface and the bare nanosubstrate of the same size and immersed in the biological sample to be tested, the scanning angle is stepped by 2°, and the maximum is 12°, the radius of the virtual circle where the four columnar nanodisks are located is D2=600nm, D1>D2, λ1>λ2, and the height of the biological sample to be tested is 250nm.

[0044] The working principle of this embodiment is: when the x-polarized wave scans the tetramer metasurface immersed in the biological sample to be tested and the bare nanosubstrate respectively, the absorption spectra A of the tetramer metasurface immersed in the biological sample to be tested and the bare nanosubstrate of the same size are respectively extracted by the spectrometer. m , A s , where the tetramer metasurface will form a quasi-BIC resonance mode, specifically the resonance mode formed by four elliptical cylindrical nanodisks on a virtual circle. At the resonance wavelength, the biological sample to be tested interacts with the induced charges on the four elliptical cylindrical nanodisks of the L×M tetramer metasurface units, making the absorption spectrum A m Significantly enhanced. Since there is a mapping relationship between the metasurface absorption enhancement factor χ at wavelength λ2 and the extinction coefficient of the biological sample, by calculating the absorption enhancement factor χ of the metasurface, the extinction coefficient of the biological sample to be tested can be determined accordingly, and the type of the biological sample can be accurately identified. The calculation formula is:

[0045]

[0046] in, They respectively represent the lower limit and upper limit of the wavelength λ2 of the x-polarized electromagnetic wave, and dλ2 represents the differential operation on λ2.

[0047] The technical effects of the present invention are further described in detail below in conjunction with simulation experiments.

[0048] 1. Simulation conditions and contents:

[0049] The simulation adopts the multi-physics simulation software COMSOL Multiphysics 6.1, and uses Floquet periodic boundary conditions to simulate the infinite array. The electromagnetic wave is incident on the metasurface along the -z direction.

[0050] Simulation 1 compares the three quasi-BIC resonance modes in Example 1 of the present invention with the results of Fano fitting. The results are as follows: Figure 4 shown.

[0051] Simulation 2 simulates the electric field distribution at the reference wavelength of the three quasi-BIC resonance modes in Example 1 of the present invention. The simulation results are as follows: Figure 5 shown.

[0052] Simulation 3, the sensitivity of the three quasi-BIC resonance modes in Example 1 of the present invention is simulated, and the simulation results are as follows: Figure 6 shown.

[0053] Simulation 4 simulates the change of the resonance mode when the electromagnetic wave sweeps the tetramer metasurface in Example 2 of the present invention. The simulation results are as follows: Figure 7 shown.

[0054] Simulation 5 simulates the absorption enhancement factor χ of the tetramer metasurface with biological samples with different extinction coefficients immersed on the upper surface in Example 2 of the present invention. The simulation results are as follows: Figure 8 shown.

[0055] 2. Simulation results and analysis:

[0056] Reference Figure 4 ,like Figure 4 As shown in (a)-(c), the x-polarized electromagnetic wave irradiates the tetramer metasurface vertically. At this time, the resonant wavelengths of the three quasi-BIC resonant modes formed by the tetramer metasurface are recorded as the initial wavelengths The three quasi-BIC resonance modes are named mode 1, mode 2, and mode 3 according to the size of the initial wavelength. It can be seen that the initial resonance wavelengths of the three quasi-BIC resonance modes are 1947.5nm, 2035.3nm, and 2139.5nm respectively; the three quasi-BIC resonances can be compared and fitted by the Fano formula, and the fitting formula is:

[0057]

[0058] Where T0 represents the resonance offset, A0 is the discrete-continuous coupling coefficient, q represents the Fano asymmetry coefficient, Γ represents the resonance width, and the fitting values ​​of the three quasi-BIC resonance modes Γ are 0.882, 0.043 and 0.542 respectively. The Q values ​​of the three quasi-BIC resonance modes can be obtained by The calculation results are 2202, 4.65×10 4 and 3910;

[0059] Reference Figure 5 , Figure 5 The electric field distributions in the xoy plane at the reference wavelengths of the three quasi-BIC resonant modes are shown respectively when the x-polarized electromagnetic wave irradiates the tetramer metasurface vertically. The gray cone and black arrow represent the electric field vector distribution and the resonant mode represented, respectively. Figure 5In (a), the electric field of mode 1 converges at the center of the four elliptical cylindrical nanodisks, and is distributed counterclockwise in the two first elliptical cylindrical nanodisks 2 and clockwise in the two second elliptical cylindrical nanodisks 3, forming a magnetic dipole closed in a circle on the yoz plane, proving that mode 1 is a toroidal dipole resonance T (toroidal dipole) in the +x direction; Figure 5 In (b), the electric field of mode 2 is concentrated at the edges of the four elliptical cylindrical nanodisks and distributed clockwise on the virtual circle, proving that mode 2 is a magnetic dipole resonance M (magnetic dipole) in the -z direction. Figure 5 In (c), the electric field of mode 3 forms two pairs of alternating positive and negative charges at the edges of the four elliptical cylindrical nanodisks near the center of the virtual circle, proving that mode 3 is an electric quadrupole resonance of the xoy plane distribution. Since the xoy plane electric field distributions of the three quasi-BIC resonance modes are completely different, it can be proved that they are independent of each other.

[0060] Reference Figure 6 , when the simulated biological sample with a thickness of 250nm is immersed in the tetramer metasurface sensor, and the refractive index n of the biological sample is changed from 1.0 to 2.0, the resonant wavelengths of the three quasi-BIC resonant modes will shift linearly from the reference wavelength, and the sensitivity of the i-th (i∈[1,2,3]) resonant mode can be expressed by The calculated values ​​are 523, 649 and 597 nm / RIU respectively. Combined with the obtained reference wavelength, the tetramer metasurface sensor can distinguish the categories of biological samples with a refractive index of 1.0-2.0.

[0061] Reference Figure 7 , the tetramer metasurface will form a quasi-BIC resonant mode. When the x-polarized electromagnetic wave is scanned with a 2° step along the normal-tangential path of the tetramer metasurface and a maximum scanning angle of 12°, the resonant modes corresponding to different scanning angles can be observed in the λ2 range of 1750-2050nm. When the upper surface of the metasurface is immersed in a biological sample, the absorption spectrum of the metasurface will be significantly enhanced at the resonant wavelength.

[0062] Reference Figure 8 , the refractive index of the biological sample to be tested immersed in the tetramer metasurface and the bare nanosubstrate of the same size is set to a fixed value n = 2.0, Figure 8 (a) to Figure 8In (d), the extinction coefficient increases from 0.01 to 0.04, and the wavelength λ2 of the scanned x-polarized electromagnetic wave ranges from 2025 to 2225 nm. The tetramer metasurface absorption enhancement factor χ is calculated, where dλ2 = 25 nm. Within the wavelength range, the maximum value of the metasurface absorption enhancement factor corresponding to the biological sample extinction coefficient from 0.01 is 15 dB, and the maximum value of the metasurface absorption enhancement factor corresponding to the biological sample extinction coefficient from 0.04 is only 10 dB. By comparing the metasurface absorption enhancement factors, the extinction coefficient of the biological sample to be tested can be determined, thereby improving the accuracy of biological sample type detection.

Claims

1. A tetramer metasurface sensor, comprising a tetramer metasurface composed of L×M periodically arranged tetramer metasurface units, a signal generator for exciting x-polarized electromagnetic waves and a spectrometer, L≥2, M≥2; the tetramer metasurface unit comprises a nanosubstrate (1) with a square cross-section and four columnar nanodisks deposited on its upper surface and uniformly distributed on the same virtual circle; characterized in that: The four columnar nanodisks are composed of two adjacent first elliptical column nanodisks (2) with long semi-axes R1 parallel to the x-axis polarization direction and two adjacent second elliptical column nanodisks (3) with long semi-axes R2 parallel to the x-axis polarization direction; the biological sample to be tested is immersed in the upper surface of the tetramer supersurface; When R1≠R2, and the wavelength of the x-polarized electromagnetic wave is λ1, and the radius of the virtual circle where the four elliptical cylindrical nanodisks are located is D1, the x-polarized electromagnetic wave irradiates the tetramer metasurface vertically from top to bottom, and the spectrometer calculates the refractive index n of the biological sample to be tested by receiving the resonant wavelengths of the three quasi-BIC resonant modes formed by the tetramer metasurface; When R1=R2, the wavelength of the x-polarized electromagnetic wave is λ2, the radius of the virtual circle where the four elliptical cylindrical nanodisks are located is D2, and D1>D2, λ1>λ2, the x-polarized electromagnetic wave is scanned from top to bottom along the normal-tangential path of the tetramer metasurface to the tetramer metasurface immersed in the biological sample to be tested and the bare nanosubstrate of the same size. The spectrometer receives the absorbance spectrum A in the broadband absorption response of the tetramer metasurface and the bare nanosubstrate. m , A s The calculated absorption enhancement factor χ of the tetramer metasurface is used to determine the extinction coefficient of the biological sample to be tested.

2. The metasurface sensor according to claim 1, characterized in that: The resonance wavelengths of the three resonance modes formed by the tetramer metasurface, wherein the three resonance modes refer to the resonance mode formed by the two first elliptical cylindrical nanodisks (2) and the two second elliptical cylindrical nanodisks (3), the resonance mode formed by the semi-major axis dimensions of the four elliptical cylindrical nanodisks, and the resonance mode formed by the four elliptical cylindrical nanodisks on a virtual circle; wherein the resonance wavelength refers to the wavelength value at which the three resonance modes respectively undergo quasi-BIC resonance within the wavelength λ1 range of the x-polarized electromagnetic wave.

3. The metasurface sensor according to claim 1, characterized in that: The nano substrate (1) and the bare nano substrate are both made of SiO2.

4. The metasurface sensor according to claim 1, characterized in that: The center of the virtual circle where the four columnar nanodisks distributed on the nanosubstrate (1) are located is located on the center normal line of the nanosubstrate (1).

5. The metasurface sensor according to claim 1, characterized in that: The two first elliptical column nano-disks (2) and the two second elliptical column nano-disks (3) are both made of Si material.

6. The metasurface sensor according to claim 1, characterized in that: The two first elliptical column nanodisks (2) and the two second elliptical column nanodisks (3) are respectively located on two diagonal lines on the upper surface of the nanosubstrate (1).

7. The metasurface sensor according to claim 5, characterized in that: The long axes of the two first elliptical column nanodisks (2) and the two second elliptical column nanodisks (3) coincide with the two diagonal lines of the upper surface of the nanosubstrate (1) on which they are located.

8. The metasurface sensor according to claim 1, characterized in that: The refractive index n of the biological sample to be tested is calculated as follows: in, They represent the resonant wavelength and reference wavelength of the i-th resonant mode when the wavelength of the x-polarized electromagnetic wave is λ1, i∈[1,2,3], S i represents the sensitivity of the i-th resonance mode.

9. The metasurface sensor according to claim 1, characterized in that: The absorption enhancement factor χ is calculated as follows: in, They respectively represent the lower limit and upper limit of the wavelength λ2 of the x-polarized electromagnetic wave, and dλ2 represents the differential operation on λ2.

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