Asymmetric double-nanopore metasurface refractive index sensor, preparation method and detection method

Abstract

The invention provides an asymmetric double-nanopore metasurface refractive index sensor, a preparation method and a detection method, and relates to the technical field of refractive index detection. The dielectric layer is formed on the surface of the substrate, a plurality of asymmetric nano-pore unit structures are formed in the dielectric layer, each asymmetric nano-pore unit structure comprises a first nano-pore and a second nano-pore, and the first nano-pore and the second nano-pore have different radiuses and / or different relative positions; structural symmetry is destroyed, and a quasi-continuum bound state resonance mode is formed; the asymmetric double-nanopore metasurface refractive index sensor is configured to generate double formants corresponding to a preset working wavelength under excitation of linear polarized light.

Description

Technical Field

[0001] The present disclosure relates to the technical field of refractive index detection, and particularly to an asymmetric double-nanopore metasurface refractive index sensor, a preparation method, and a detection method. Background Art

[0002] Refractive index detection plays an important role in scientific research and industrial applications, and its accurate measurement is crucial for multiple fields such as materials, food, biology, medicine, and the environment. The refractive index measurement can determine the concentration of sample components by measuring the refractive index of a solution and combining it with a known concentration-refractive index standard curve.

[0003] Currently, using an Abbe refractometer is a commonly used refractive index detection method in industry and scientific research. However, in addition to the influence of environmental sensitivity, this method also requires regular calibration and maintenance of the instrument to maintain its measurement accuracy. At the same time, there are many limitations on the samples that the instrument can measure. For example, it cannot complete the refractive index measurement of corrosive liquids such as acids and alkalis. In addition, the multi-dimensional detection requirements of biomolecules cannot be met. The huge detection demand brought about by the above limitations requires the development of a fast refractive index detection method with simple operation and wide application range. Summary of the Invention

[0004] In view of the above problems, the present disclosure provides an asymmetric double-nanopore metasurface refractive index sensor, a preparation method, and a detection method, which are used to at least partially solve the above technical problems.

[0005] According to a first aspect of an embodiment of the present disclosure, an asymmetric double-nanopore metasurface refractive index sensor is provided, including: a substrate; a dielectric layer formed on the surface of the substrate, and a plurality of asymmetric nanopore unit structures are formed in the dielectric layer. The asymmetric nanopore unit structure includes a first nanopore and a second nanopore, and the first nanopore and the second nanopore have different radii and / or different relative positions to break the structural symmetry and form a quasi-continuous bound state resonance mode; the asymmetric double-nanopore metasurface refractive index sensor is configured to generate double resonance peaks corresponding to a predetermined working wavelength under the excitation of linearly polarized light.

[0006] According to an embodiment of the present disclosure, the asymmetric nanopore unit structures are periodically arranged in the dielectric layer, the first period along the first direction is 350 nm to 450 nm, the second period along the second direction is 160 nm to 240 nm, and the first direction is orthogonal to the second direction.

[0007] According to an embodiment of the present disclosure, the radius of the first nanopore is 50 nm to 90 nm, and the radius of the second nanopore is 50 nm to 60 nm.

[0008] According to an embodiment of the present disclosure, a first distance from the center of the first nanopore to the central symmetry axis of the asymmetric nanopore unit structure is 90 nm to 110 nm; a second distance from the center of the second nanopore to the central symmetry axis of the asymmetric nanopore unit structure is 90 nm to 110 nm, and an absolute value of a difference between the first distance and the second distance is 0 nm to 15 nm.

[0009] According to an embodiment of the present disclosure, a predetermined operating wavelength is 350 nm to 1000 nm.

[0010] According to an embodiment of the present disclosure, the substrate includes one of a quartz substrate, a glass substrate, and a sapphire substrate, and the material of the dielectric layer includes one of silicon, silicon dioxide, and silicon nitride.

[0011] According to an embodiment of the present disclosure, the thickness of the substrate is 0.21 mm to 1 mm, and the thickness of the dielectric layer is 80 nm to 120 nm.

[0012] According to a second aspect of an embodiment of the present disclosure, a method for manufacturing an asymmetric double-nanopore metasurface refractive index sensor is provided, including: forming a dielectric layer on a substrate, and forming a photoresist layer on the dielectric layer; exposing and developing the photoresist layer to form a photoresist pattern on the photoresist layer; forming a metal layer on the developed photoresist layer and the exposed dielectric layer, removing the photoresist layer and the metal layer on the photoresist layer to obtain a sample; etching the sample to form a plurality of asymmetric double-nanopore unit structures, where the asymmetric nanopore unit structure includes a first nanopore and a second nanopore, and the first nanopore and the second nanopore have different radii and / or different relative positions to break the structural symmetry and form a quasi-bound state resonance mode of a continuum; removing the metal layer to obtain the asymmetric double-nanopore metasurface refractive index sensor.

[0013] According to a third aspect of an embodiment of the present disclosure, a refractive index detection method is provided, characterized in that the refractive index detection method is implemented based on the above-mentioned asymmetric double-nanopore metasurface refractive index sensor, and the method includes: respectively dropping a plurality of different refractive index solutions onto the surface of the asymmetric double-nanopore metasurface refractive index sensor, and collecting respective first transmission spectral signals; determining a relationship between the refractive index and the resonance peak wavelength based on the plurality of first transmission spectral signals; dropping a sample to be measured onto the surface of the asymmetric double-nanopore metasurface refractive index sensor, and collecting a second transmission spectral signal; determining the refractive index of the sample to be measured based on the relationship between the refractive index and the resonance peak wavelength and the second transmission spectral signal.

[0014] According to an embodiment of the present disclosure, the sample to be measured includes one of a gas, a liquid, and a biomolecule.

[0015] The asymmetric double-nanopore metasurface refractive index sensor, preparation method, and detection method provided by the present disclosure have at least the following technical effects:

[0016] By arranging an asymmetric nanopore unit structure in the dielectric layer, when the refractive index of the surface of the sensor changes due to the sample to be measured, the resonance peak of the sensor will shift. According to the change of the resonance peak shift, the change of the refractive index of the sample can be measured, so as to quickly and effectively identify the properties of the sample to be measured, such as composition and concentration.

[0017] Since the first nanopore and the second nanopore have different radii and / or different relative positions, the structural symmetry can be broken and a quasi-bound state resonance mode of the continuum can be formed. The quasi-bound state resonance mode of the continuum is used to further improve the sharpness of the resonance peak of the metasurface. Theoretical calculations show that the quality factor of this metasurface structure can reach 2250, which is significantly higher than that of many existing visible light refractive index sensors.

[0018] The sensor of this structure generates double resonance peaks (located in the visible light and near-infrared bands respectively) corresponding to a predetermined working wavelength (350 nm - 1000 nm) under the excitation of linearly polarized light, which is adapted to the spectral response range of a complementary metal oxide semiconductor (CMOS) image sensor, ensuring compatibility with CMOS technology. Thus, imaging or microfluidic modules can be freely added to meet the continuous monitoring requirements of different samples.

[0019] The sensor of this structure achieves a sensing sensitivity of 151.6 nm / RIU, and the measurement error is about 2.3%, which can accurately and stably detect small refractive index changes.

[0020] The sensor of this structure can be widely applied to the fields of biosensing, environmental monitoring, chemical analysis, etc., and has the advantages of high sensitivity, high stability, high signal-to-noise ratio, and wide application range. Description of the Drawings

[0021] Through the following description of the embodiments of the present disclosure with reference to the drawings, the above content and other purposes, features, and advantages of the present disclosure will become clearer. In the drawings:

[0022] Figure 1 Schematically shows the overall structure diagram of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure;

[0023] Figure 2 Schematically shows the top view structure diagram of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure;

[0024] Figure 3Schematically shows the preparation flow chart of an asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure;

[0025] Figure 4 Schematically shows the diagram of the simulated transmission spectrum change of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure under different position differences;

[0026] Figure 5 Schematically shows the diagram of the simulated transmission spectrum change of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure under different radius differences;

[0027] Figure 6 Schematically shows the trend diagram of the change of the quality factor Q of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure under different position difference conditions;

[0028] Figure 7 Schematically shows the bright-field microscope image and SEM image of the BIC array of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure;

[0029] Figure 8 Shows the transmission spectrum curve diagram of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure at different refractive indices. Detailed implementation manners

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present disclosure. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, obviously, one or more embodiments can also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.

[0031] In the process of implementing the present disclosure, it is found that: using metasurfaces to complete refractive index sensing is widely applied in the biomedical field. Metasurfaces with specific patterns have sharp resonance peaks. When biomolecules interact with the metasurface, the local refractive index changes, thereby causing the resonance peak of the sensor to shift. According to the change of the resonance peak shift, the change of the refractive index of the sample can be measured. This detection method does not require labeling of biomolecules and has the characteristics of real-time, fast and high sensitivity, making up for the deficiencies of traditional refractive index detection methods (such as Abbe refractometers) in biomolecule detection. In addition, the design flexibility of the metasurface structure shows great potential in the development of biosensors.

[0032] With the progress of technology, the requirements for refractive index measurement in terms of accuracy, intelligence, and integration are constantly increasing. The combination of all-dielectric metasurfaces and bound states in the continuum (BIC) modes is an effective means to improve the accuracy of refractive index detection. BIC is an ideal state where the electromagnetic mode is completely confined within a limited region. Therefore, in theory, BIC has an infinite quality factor. Under practical conditions, the destruction of the symmetry of the micro-nano structure leads to a small radiation loss, and the BIC mode is decoupled. At this time, BIC is transformed into quasi-BIC, which can provide sharp resonance peaks for the metasurface, thereby improving its refractive index measurement accuracy; all-dielectric metasurfaces have low loss and good biocompatibility, and can be combined with microfluidic technology and CMOS sensors to broaden their functionality, and realize continuous monitoring of the refractive index of the responsible sample based on images.

[0033] In view of this, the embodiments of the present disclosure provide an asymmetric double-nanopore metasurface refractive index sensor, a preparation method, and a detection method to achieve high-stability, high-repeatability, and high-sensitivity refractive index detection.

[0034] Figure 1 The overall structure diagram of the asymmetric double-nanopore metasurface refractive index sensor according to the embodiments of the present disclosure is schematically shown.

[0035] As Figure 1 shown, the asymmetric double-nanopore metasurface refractive index sensor of this embodiment may include: a substrate 1 and a dielectric layer 2 formed on the surface of the substrate 1.

[0036] A plurality of asymmetric nanopore unit structures may be formed in the dielectric layer 2. Each asymmetric nanopore unit structure includes a first nanopore 21 and a second nanopore 22, and the first nanopore 21 and the second nanopore 22 have different radii and / or different relative positions to destroy the structural symmetry and form a bound state in the continuum resonance mode.

[0037] According to the embodiments of the present disclosure, the asymmetric double-nanopore metasurface refractive index sensor is configured to generate double resonance peaks corresponding to a predetermined working wavelength under the excitation of linearly polarized light.

[0038] In some embodiments, the asymmetric nanopore unit structures are periodically arranged in the dielectric layer. For example, Figure 1 the larger round hole in

[0039] is the first nanopore 21, and the smaller round hole is the second nanopore 22, and the large and small round holes are periodically arranged in the dielectric layer 2. The first period along the first direction may be 350 nm to 450 nm, and the second period along the second direction may be 160 nm to 240 nm. The first direction may be orthogonal to the second direction.

[0040] For example, taking the cross-sectional shape of the dielectric layer 2 as a rectangle, the first period Px along the long side direction (the first direction) of the dielectric layer 2 can be 350 nm to 450 nm, and the second period Py along the short side direction (the second direction) of the dielectric layer 2 can be 160 nm to 240 nm.

[0041] Figure 2 The top view structural diagram of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure is schematically shown.

[0042] As Figure 2 shown, in some embodiments, the radius R1 of the first nanopore 21 is 50 nm to 90 nm, and the radius R2 of the second nanopore 22 is 50 nm to 60 nm.

[0043] For example, the radius R1 of the first nanopore 21 is 50 nm, 55 nm or 60 nm, and the radius R2 of the second nanopore 22 is 50nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm or 90 nm.

[0044] Continuing to refer to Figure 2 , in some embodiments, the first distance d1 from the center of the first nanopore 21 to the central symmetry axis of the asymmetric nanopore unit structure is 90 nm to 110 nm; the second distance d2 from the center of the second nanopore 22 to the central symmetry axis of the asymmetric nanopore unit structure is 90 nm to 110 nm, and the absolute value of the difference between the first distance d1 and the second distance d2 is 0 nm to 15 nm.

[0045] For example, the absolute value of the difference (position difference) between the first distance d1 and the second distance d2 is 0 nm, 5 nm, 10 nm or 15 nm.

[0046] The central symmetry axis of the asymmetric nanopore unit structure can be understood as the central symmetry axis of the cross-sectional shape corresponding to the asymmetric nanopore unit structure. As Figure 2 shown, for example, if the cross-sectional shape corresponding to the asymmetric nanopore unit structure is a rectangle, the central symmetry axis can refer to the axis perpendicular to the long side of the rectangle and passing through the geometric center of the rectangle, and this axis divides the rectangle into two symmetric parts on the left and right, and the first nanopore 21 and the second nanopore 22 are located on both sides of the central symmetry axis.

[0047] In some embodiments, the substrate 1 can include one of a quartz substrate, a glass substrate, and a sapphire substrate, and the material of the dielectric layer 2 can include one of silicon, silicon dioxide, and silicon nitride.

[0048] In some embodiments, the thickness of the substrate 1 can be 0.21 mm to 1 mm, and the thickness of the dielectric layer 2 can be 80 nm to 120 nm.

[0049] In some embodiments, the predetermined working wavelength is 350 nm to 1000 nm. This predetermined working wavelength can correspond to the working wavelength of a color CMOS sensor.

[0050] Embodiments of the present disclosure also provide a method for fabricating an asymmetric double-nanopore metasurface refractive index sensor for fabricating the above-mentioned asymmetric double-nanopore metasurface refractive index sensor.

[0051] In some embodiments, the fabrication method may include:

[0052] Form a dielectric layer on the substrate, and form a photoresist layer on the dielectric layer.

[0053] Expose and develop the photoresist layer to form a photoresist pattern on the photoresist layer.

[0054] Form a metal layer on the developed photoresist layer and the exposed dielectric layer, and remove the photoresist layer and the metal layer on the photoresist layer to obtain a sample.

[0055] Etch the sample to form a plurality of asymmetric double-nanopore unit structures, wherein the asymmetric nanopore unit structure includes a first nanopore and a second nanopore, and the first nanopore and the second nanopore have different radii and / or different relative positions to break the structural symmetry and form a quasi-bound state resonance mode of the continuum.

[0056] Remove the metal layer to obtain the asymmetric double-nanopore metasurface refractive index sensor.

[0057] In fact, for the first nanopore and the second nanopore of the asymmetric nanopore unit structure in the present disclosure, at least one of radius asymmetry or relative position asymmetry needs to be satisfied to break the structural symmetry and form a quasi-bound state resonance mode of the continuum.

[0058] Figure 3 Schematically shows a flowchart of the fabrication of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure.

[0059] As Figure 3 shown, a specific example of the fabrication method can be:

[0060] Step 1: Clean the substrate, deposit 100 nm of silicon on the substrate using Chemical Vapor Deposition (CVD), and then spin-coat a photoresist, such as an electron beam resist;

[0061] Step 2: Expose the designed pattern on the photoresist using Electron Beam Lithography (EBL).

[0062] Step 3: Develop the photoresist to form the desired photoresist pattern, and then deposit a 10-nm chromium layer on the surfaces of the photoresist and the dielectric layer.

[0063] Step 4: Remove the photoresist. Since silicon has poor conductivity, the presence of the chromium layer is beneficial for high-resolution imaging of the sample using FIB or SEM after removing the photoresist to preliminarily determine the structural dimensions.

[0064] Step 5: Etch the sample to form multiple asymmetric nanohole unit structures. Inductively Coupled Plasma (ICP) dry etching or Reactive Ion Etching (RIE) can be used.

[0065] Step 6: Remove the Cr metal layer to obtain the asymmetric double-nanohole metasurface refractive index sensor.

[0066] Based on the above asymmetric double-nanohole metasurface refractive index sensor, an embodiment of the present disclosure also provides a refractive index detection method.

[0067] The refractive index detection method may include:

[0068] Drop a variety of different refractive index solutions onto the surface of the asymmetric double-nanohole metasurface refractive index sensor respectively, and collect their first transmission spectral signals.

[0069] Determine the relationship between the refractive index and the resonance peak wavelength based on multiple first transmission spectral signals;

[0070] Drop the sample to be measured onto the surface of the asymmetric double-nanohole metasurface refractive index sensor, and collect the second transmission spectral signal.

[0071] Determine the refractive index of the sample to be measured based on the relationship between the refractive index and the resonance peak wavelength and the second transmission spectral signal.

[0072] According to the embodiment of the present disclosure, the sensor can be calibrated using standard refractive index solutions with known refractive indices. The transmission spectral signals can be collected using a spectrometer, and the resonance peak wavelengths corresponding to each standard refractive index solution are recorded. Solutions with different refractive indices will cause the resonance peaks to shift. Based on the relationship between the refractive index and the resonance peak wavelength obtained through experiments, a linear relationship database between the refractive index and the resonance peak wavelength is constructed, and this database will be used as a benchmark for subsequent refractive index detection to calculate the refractive index of the sample to be measured.

[0073] The sample to be measured can include one of gas, liquid, and biomolecules. The liquid can include a solution. During the detection process, the light source and environmental conditions (temperature) need to be kept stable.

[0074] According to the calibration database and the resonance spectral wavelength information of the sample to be measured obtained, by using the interpolation analysis method, the refractive index of the sample to be measured can be accurately calculated.

[0075] Figure 4 Schematically shows a diagram of the simulated transmission spectrum change of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure at different position differences.

[0076] As Figure 4 shown, when the position difference is 0, the position symmetry of the double nanopores is not broken, and there is no resonance peak in the transmission spectrum at this time. The change in the position difference realizes the decoupling of the BIC mode and opens the leakage channel. As the position difference increases, resonance peaks begin to appear, and the peak-valley difference and linewidth gradually increase.

[0077] Figure 5 Schematically shows a diagram of the simulated transmission spectrum change of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure at different radius differences.

[0078] As Figure 5 shown, the decoupling method of the asymmetric double-nanopore metasurface refractive index sensor is by modifying the radius difference of the double nanopores. The two BICs with working bands located in the visible light and near-infrared bands are respectively named BIC I and BIC II. The BIC decoupling modes of the two are independent of each other, but both are in the form of symmetry breaking, that is, the former breaks the radius symmetry of the double nanopores, and the latter breaks the position symmetry of the double nanopores.

[0079] Figure 5 In a, it shows the change of the transmission spectrum of BIC I when R1 = 50 nm and R2 increases from 50 nm to 75 nm. The rule is similar to Figure 4 that shown by BIC II in b of the figure. As the degree of symmetry breaking increases, the height difference and linewidth of the resonance peak gradually increase, and the sharpness of the resonance peak gradually decreases. Symmetry-protected BIC is usually closely related to Fano resonance. The resonance peaks of BIC I and BIC II show typical Fano lines. Therefore, the following Fano formula can be used to fit the resonance peaks, where ω0 is the resonant frequency, a, b, and c are constants, γ is related to the resonance peak linewidth, and the quality factor Q = ω0 / 2γ.

[0080]

[0081] It should be understood that the above fitting formula is for more clearly explaining the embodiments of the present disclosure and does not limit the present disclosure.

[0082] Figure 6 Schematically shows the variation trend diagram of the quality factor Q under different position difference conditions of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure.

[0083] As Figure 6 shown, as the line width becomes narrower, the quality factor of the resonance peak gradually increases. When the position difference is 2 nm, the quality factor can reach 2250. However, in fact, as Figure 4 shown, as the line width becomes narrower, the difference between the peak and valley of the resonance peak also decreases. Therefore, in order to ensure the feasibility of the device, it is necessary to appropriately limit the quality factor.

[0084] To more clearly prove the feasibility of the asymmetric double-nanopore metasurface refractive index sensor, preparation method and detection method provided by the embodiments of the present disclosure, specific examples and corresponding experimental data are provided below for illustration.

[0085] In this example, three groups of asymmetric double-nanopore metasurface refractive index sensors with different position differences are prepared by the above method for detection. On the substrate silicon wafer, the periods Px and Py are 400 nm and 200 nm respectively, the radius R1 of the first nanopore is 40 nm, the radius R2 of the second nanopore is 60 nm, and the position differences of the nanopores are 0 nm, 5 nm, and 10 nm respectively. The thickness h of the dielectric layer Si is 100 nm.

[0086] Figure 7 Schematically shows the bright-field microscope image and SEM image of the BIC array of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure.

[0087] As Figure 7 shown, the SEM image is based on the alignment of the circular hole edges to show the change of the position difference (Δ). By comparing the nanopore edges of serial numbers A and C, the nanopore position difference can be found, but the difference between A and B is not obvious. The subsequent experiments are completed using the structure of serial number C. In fact, during the actual processing, due to the influence of the exposure dose and etching parameters, there is a certain gap between the processed size and the expected value. The specific sizes of the samples obtained according to the SEM images are shown in Table 1 below.

[0088] Table 1 List of specific sizes of samples

[0089]

[0090] Figure 8 Shows the transmission spectral curve diagram of the asymmetric double-nanopore metasurface refractive index sensor according to an embodiment of the present disclosure at different refractive indices.

[0091] As Figure 8As shown, the experiment was calibrated using a refractive index matching fluid. The refractive indices of the used refractive index matching fluids were 1.3978, 1.4477, 1.4967, 1.5453, and 1.5937 respectively. The refractive index sensitivity of the obtained sensor (the ratio of wavelength change to refractive index change Δλ / Δn) was 151.6 nm / RIU. Compared with some all-dielectric BIC refractive index sensors, the sensitivity of BIC I was improved. The obtained resonance wavelength had a linear relationship with the refractive index. Taking the matching fluid with a refractive index of 1.4477 as an example for error analysis, the obtained experimental error was 2.58%. Moreover, the sensor accuracy could be further improved by increasing the amount of calibration data. For example, the refractive index step used in this calibration experiment was 0.05, and the step could be reduced to 0.01 to improve the measurement accuracy.

[0092] The above describes the embodiments of the present disclosure. However, these embodiments are merely for illustrative purposes and not for limiting the scope of the present disclosure. Although the embodiments are described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, and these substitutions and modifications should all fall within the scope of the present disclosure.

Claims

1. An asymmetric double-nanopore metasurface refractive index sensor, characterized in that, Comprising: A substrate; A dielectric layer formed on the surface of the substrate, in which a plurality of asymmetric nanopore unit structures are formed. The asymmetric nanopore unit structure includes a first nanopore and a second nanopore, and the first nanopore and the second nanopore have different radii and / or different relative positions to break the structural symmetry and form a quasi - continuous bound state resonance mode; The asymmetric double - nanopore metasurface refractive index sensor is configured to generate a double resonance peak corresponding to a predetermined operating wavelength under the excitation of linearly polarized light.

2. The sensor according to claim 1, characterized in that, The asymmetric nanopore unit structures are periodically arranged in the dielectric layer. The first period along a first direction is 350 nm - 450 nm, and the second period along a second direction is 160 nm - 240 nm. The first direction is orthogonal to the second direction.

3. The sensor according to claim 2, wherein The radius of the first nanopore is 50 nm - 90 nm, and the radius of the second nanopore is 50 nm - 60 nm.

4. The sensor according to claim 3, wherein The first distance from the center of the first nanopore to the central symmetry axis of the asymmetric nanopore unit structure is 90 nm - 110 nm; the second distance from the center of the second nanopore to the central symmetry axis of the asymmetric nanopore unit structure is 90 nm - 110 nm, and the absolute value of the difference between the first distance and the second distance is 0 nm - 15 nm.

5. The sensor according to claim 1, characterized in that The predetermined operating wavelength is 350 nm - 1000 nm.

6. The sensor according to claim 1, characterized in that, The substrate includes one of a quartz substrate, a glass substrate, and a sapphire substrate, and the material of the dielectric layer includes one of silicon, silicon dioxide, and silicon nitride.

7. The sensor according to claim 1 or 6, characterized in that, The thickness of the substrate is 0.21 mm - 1 mm, and the thickness of the dielectric layer is 80 nm - 120 nm.

8. A preparation method of an asymmetric double-nanopore metasurface refractive index sensor, characterized in that, Comprising: Forming a dielectric layer on the substrate and forming a photoresist layer on the dielectric layer; Exposing and developing the photoresist layer to form a photoresist pattern on the photoresist layer; Forming a metal layer on the developed photoresist layer and the exposed dielectric layer, and removing the photoresist layer and the metal layer on the photoresist layer to obtain a sample piece; Etching the sample piece to form a plurality of asymmetric double - nanopore unit structures, wherein the asymmetric nanopore unit structure is composed of a first nanopore and a second nanopore, and the first nanopore and the second nanopore have different radii and / or different relative positions to break the structural symmetry and form a quasi - continuous bound state resonance mode; Removing the metal layer to obtain an asymmetric double - nanopore metasurface refractive index sensor.

9. A refractive index detection method, characterized in that The refractive index detection method is implemented based on the asymmetric double - nanopore metasurface refractive index sensor according to any one of claims 1 - 7. The method includes: Respectively dropping a plurality of different refractive index solutions onto the surface of the asymmetric double - nanopore metasurface refractive index sensor and collecting respective first transmission spectral signals; Determining the relationship between the refractive index and the resonance peak wavelength based on the plurality of first transmission spectral signals; Dropping a sample to be measured onto the surface of the asymmetric double - nanopore metasurface refractive index sensor and collecting a second transmission spectral signal; Determine the refractive index of the sample to be measured based on the relationship between the refractive index and the resonance peak wavelength and the second transmission spectrum signal.

10. The detection method according to claim 9, characterized in that The sample to be measured includes one of gas, liquid, and biomolecule.

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