All-dielectric metasurface chiral sensor based on BIC

Abstract

The invention provides an all-dielectric metasurface chiral sensor based on a BIC. The all-dielectric metasurface chiral sensor comprises a plurality of all-dielectric metasurface units which are periodically arranged, a signal generator and a spectrograph, each all-dielectric metasurface unit comprises a nano substrate and a nano block fixed on the upper surface of the nano substrate; the nano block is provided with two asymmetric nano cylindrical cavities, the central axis of one nano cylindrical cavity is located on one diagonal plane of the nano block, the central axis of the other nano cylindrical cavity is located at the position deviating from the diagonal plane, and the offset delta l and the offset direction are determined through the maximum amplitude of the circular dichroism CD. According to the invention, the degree of asymmetry is regulated and controlled through the radius of the cross section circle of the nano cylindrical cavity, so that high quality factor and high-efficiency response of CD maximum amplitude are realized, the metasurface unit has excellent optical resonance characteristic and extremely narrow resonance line width, and the resolution and detection capability of the sensor are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of optical sensing technology and relates to a chiral sensor, specifically to a chiral sensor based on a continuum bound state BIC all-dielectric metasurface, which can be used in the fields of biochemical analysis, medical diagnosis and environmental monitoring. Technical Background

[0002] Metasurface sensors are photoelectric sensors composed of periodically arranged metasurface sensitive elements, signal generators, and spectrometer conversion elements. They are used to accurately and sensitively detect the physical quantity of the object to be detected. According to the differences in the optical properties of the object to be detected and the sensing principle, metasurface sensors can be divided into metasurface chiral sensors, metasurface transmission sensors, and metasurface reflection sensors.

[0003] The metasurface chiral sensor is a photoelectric sensor designed based on the principle of circular dichroism (CD). It uses the different responses of the chiral structure to left-handed circularly polarized waves and right-handed circularly polarized waves to distinguish chiral molecules. Its basic structure is usually composed of multiple subwavelength units arranged in a specific pattern to produce strong optical chirality, thereby achieving ultra-sensitive sensing detection of chiral molecules.

[0004] Traditional metasurface chiral sensors rely on circular dichroism (CD) spectroscopy, but suffer from low sensitivity, slow response speed or complex operation. To overcome these limitations, researchers explored ways to enhance chiral response by setting up asymmetric structures and introducing continuum bound states (BICs). BICs are a special physical phenomenon in which specific modes can exist in the continuous spectrum without being affected by radiation losses. The electromagnetic wave resonance Q value of this mode can reach 10 times that of other structures in the spectrometer. 2 -10 3 times, showing its great application potential in the field of chiral sensing. More specifically, the structure is constructed by simultaneously introducing in-plane inversion and mirror asymmetry to achieve narrow linewidth high-quality factor chiral sensing.

[0005] The existing BIC-based all-dielectric metasurface chiral sensor is composed of multiple periodically arranged all-dielectric metasurface units, a signal generator and a spectrometer. The all-dielectric metasurface unit includes a silicon dioxide substrate with a square cross-section and a square silicon block placed on it. This chiral sensor introduces BIC by cutting off two asymmetric rectangular blocks on both sides of the square silicon block to improve the detection accuracy. The chiral structure is used to achieve chiral sensing while the quality factor can reach 6×10 4 The transmission response in the terahertz and infrared domains shows a value close to 10 4 RIU -1However, since the asymmetric structure of its metasurface unit and the chiral structure cannot be modulated more harmoniously, the quality factor of its BIC and the FOM of chiral sensing are low, resulting in the high spectral resolution of the chiral sensor is still low. Summary of the invention

[0006] The purpose of the present invention is to address the problems existing in the prior art and propose an all-dielectric metasurface chiral sensor based on BIC to solve the technical problem of low detection accuracy caused by the low quality factor of BIC and the excellent value of chiral sensing in the prior art.

[0007] To achieve the above-mentioned purpose, the present invention includes a plurality of periodically arranged all-dielectric metasurface units, as well as a signal generator and a spectrometer; the all-dielectric metasurface unit includes a nano-substrate 1 and a nano-block 2 fixed on its upper surface; the nano-block 2 adopts a tetrahedral structure with a square cross-section, on which are arranged a first nano-cylindrical cavity 3 and a second nano-cylindrical cavity 4 that penetrate the upper and lower surfaces and are asymmetric about the central axis of the nano-block 2, for realizing the continuum bound state BIC characteristics, wherein the central axis of the first nano-cylindrical cavity 3 is located on a diagonal plane of the nano-block 2, and the central axis of the second nano-cylindrical cavity 4 is located at a position offset from the diagonal plane, and the offset Δl and the offset direction are determined by the maximum amplitude of the circular dichroism CD.

[0008] In the above-mentioned all-dielectric metasurface chiral sensor, the nano substrate 1 is a silicon dioxide plate having a square surface shape.

[0009] In the above-mentioned all-dielectric metasurface chiral sensor, the nanoblock 2 is made of a semiconductor material of silicon, silicon nitride or gallium arsenide.

[0010] In the above-mentioned all-dielectric metasurface chiral sensor, the center normal line of the nanoblock 2 coincides with the center normal line of the nanosubstrate 1 .

[0011] In the above-mentioned all-dielectric metasurface chiral sensor, the central axis of the second nano-cylindrical cavity 4 is parallel to the central axis of the first nano-cylindrical cavity 3 .

[0012] In the above-mentioned all-dielectric metasurface chiral sensor, the central axes of the first nanocylindrical cavity 3 and the second nanocylindrical cavity 4 are parallel to the central normal of the nano substrate 1 .

[0013] In the above-mentioned all-dielectric metasurface chiral sensor, the maximum amplitude of the circular dichroism refers to the maximum value of the circular dichroism calculated by the spectrometer through the transmittance of the left-handed circularly polarized wave transmitted by the left-handed circularly polarized wave and the right-handed circularly polarized wave converted therefrom, and the right-handed circularly polarized wave transmitted by the right-handed circularly polarized wave and the left-handed circularly polarized wave converted therefrom, when the left-handed circularly polarized wave and the right-handed circularly polarized wave are vertically irradiated from top to bottom by the signal generator, wherein the calculation formula of CD is:

[0014]

[0015] Among them, T l 、T r They represent the total transmittance of the transmitted left-hand circularly polarized wave and right-hand circularly polarized wave respectively.

[0016] In the above-mentioned all-dielectric metasurface chiral sensor, the quality factor Q of the continuum bound state BIC is calculated by regulating the asymmetry α through the cross-sectional areas of the first nanocylindrical cavity 3 and the second nanocylindrical cavity 4, wherein the calculation formulas of α and Q are respectively:

[0017]

[0018] Wherein, ΔS is the sum of the cross-sectional areas of the first nanocylindrical cavity and the second nanocylindrical cavity, S is the cross-sectional area of ​​the nanoblock, ω is the complex frequency, r is the radius of the first nanocylindrical cavity and the second nanocylindrical cavity, l is the side length of the cross-sectional area of ​​the nanoblock, and Re(·) and Im(·) are the real and imaginary part operations, respectively.

[0019] When the above-mentioned all-dielectric metasurface chiral sensor detects the physical change of the object to be detected, the object to be detected is first covered on the upper surface of the metasurface, and the left-handed circularly polarized wave and the right-handed circularly polarized wave emitted by the signal generator are vertically irradiated from top to bottom. The wavelength change value Δλ transmitted by the metasurface structure and the CD curve of the chiral sensor are compared and analyzed by a spectrometer to obtain the physical change of the object to be detected.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The all-dielectric metasurface unit of the present invention adopts a nano-cylindrical cavity structure that penetrates the upper and lower surfaces of the tetrahedral nano-block and is asymmetric about the central axis of the nano-block, which can realize the continuum bound state BIC characteristics, and the asymmetry is regulated by the radius of the cross-sectional circle of the nano-cylindrical cavity, thereby achieving a high degree of 2.14×10 5 The quality factor of the metasurface unit gives it excellent optical resonance characteristics and extremely narrow resonance linewidth, which significantly improves the resolution of the sensor.

[0022] 2. The present invention determines the offset and direction of the central axis of the second nanocylindrical cavity relative to a diagonal plane of the nanoblock where the central axis of the first nanocylindrical cavity is located by the maximum amplitude of the circular dichroism CD, and accurately achieves efficient response to the maximum amplitude of CD. The experimental results show that the excellent sensitivity value of the chiral response in the present invention reaches 7.51×10 4 RIU -1 , greatly enhancing the high spectral resolution and detection capabilities of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0024] Figure 2 is a schematic structural diagram of an all-dielectric metasurface unit according to an embodiment of the present invention;

[0025] Figure 3 is a top view of an all-dielectric metasurface unit according to an embodiment of the present invention;

[0026] Figure 4 is a graph showing the relationship between the circular dichroism amplitude and the central axis offset Δl of the second nanocylindrical cavity under different conditions of the present invention;

[0027] Figure 5 Schematic diagram of the relationship between the Q factor and the asymmetry α under different conditions of the offset Δl of the central axis of the second nanocylindrical cavity under the present invention;

[0028] FIG6 is a normalized electric field distribution simulation diagram of an embodiment of the present invention;

[0029] 7 is a simulation comparison diagram of the transmission response component and the time coupled mode theory fitting of an embodiment of the present invention;

[0030] FIG. 8 is a performance diagram of chiral sensing in terms of sensitivity and excellence value according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0032] Reference Figure 1 The present invention includes M×N periodically arranged all-dielectric metasurface units, and a signal generator and a spectrometer for exciting left-handed circularly polarized waves and right-handed circularly polarized waves, M≥2, N≥2, and in this embodiment M=8, N=8.

[0033] Reference Figure 2The all-dielectric metasurface unit includes a nanosubstrate 1 with a square cross section and a side length of 4800nm ​​and a nanoblock 2 fixed on its upper surface; the nanoblock 2 adopts a tetrahedral structure with a square cross section, a height of 230nm, and a side length of 400nm. The center normal of the nanoblock 2 coincides with the center normal of the nanosubstrate 1. The material of the nanosubstrate 1 is silicon dioxide with good insulation and stable chemical properties. The material of the nanoblock 2 is Si3N4, a semiconductor material with high electron mobility and high photoelectric conversion efficiency, and its characteristics are suitable for making metasurface sensors with high requirements for response speed and sensitivity.

[0034] Reference Figure 3 The nanoblock 2 is provided with a first nanocylindrical cavity 3 and a second nanocylindrical cavity 4 that penetrate the upper and lower surfaces and are asymmetric about the central axis of the nanoblock 2, and the radius of the cross-section circle is r. The central axes of the first nanocylindrical cavity 3 and the second nanocylindrical cavity 4 are parallel to the central normal of the nanosubstrate 1. Through the structure of the double nanocylindrical cavity, the in-plane inversion symmetry of the all-dielectric metasurface unit is broken, and the continuum bound state BIC characteristics are realized in the structure.

[0035] The central axis of the first nanocylindrical cavity 3 is located on a diagonal plane of the nanoblock 2, and the distance d from the central axis of the nanoblock 2 is 105nm. The central axis of the second nanocylindrical cavity 4 is located at a position offset from the diagonal plane, and when the offset Δl is 0, the distance d from the central axis of the nanoblock 2 is also 105nm. When the central axis of the second nanocylindrical cavity 4 is offset from the position of the diagonal plane, it is used to realize the circular dichroism CD characteristic. The offset direction is adjusted to the left and right polarization circular characteristic states in the polarization characteristic diagram according to the polarization evolution distribution of the topological properties in the momentum space. At this time, the circular dichroism CD can reach the maximum amplitude, that is, the central axis of the second nanocylindrical cavity 4 is laterally offset from the diagonal plane of the nanoblock 2 where the central axis of the first nanocylindrical cavity 3 is located. It is assumed that when it is offset to the left, the offset Δl is positive, and when it is offset to the right, the offset Δl is negative.

[0036] Then, the amplitude of circular dichroism is observed by adjusting the offset Δl of the central axis of the second nanocylindrical cavity 4 from -60nm to 60nm. When the CD amplitude of circular dichroism is the largest, the value of Δl is selected. At this time, the chiral sensing accuracy is the largest, which is convenient for using the all-dielectric metasurface chiral sensor for accurate detection of analyte sensing. One simulation method is to use the left-handed circularly polarized wave and the right-handed circularly polarized wave emitted by the signal generator to vertically irradiate the all-dielectric metasurface from top to bottom. After the left-handed circularly polarized wave irradiated on the all-dielectric metasurface is transmitted, a part is still a left-handed circularly polarized wave, and the other part is converted to a right-handed circularly polarized wave. After the right-handed circularly polarized wave irradiated on the all-dielectric metasurface is transmitted, a part is still a right-handed circularly polarized wave, and the other part is converted to a left-handed circularly polarized wave. The spectrometer calculates the maximum value of circular dichroism CD by receiving the transmittance of the part of the left-hand circularly polarized wave transmitted by the left-hand circularly polarized wave and the right-hand circularly polarized wave converted therefrom, as well as the part of the right-hand circularly polarized wave transmitted by the right-hand circularly polarized wave and the left-hand circularly polarized wave converted therefrom, wherein the calculation formula of CD is:

[0037]

[0038] Among them, T l 、T r They represent the total transmittance of the transmitted left-hand circularly polarized wave and right-hand circularly polarized wave respectively.

[0039] Reference Figure 4 , the change of the central axis offset Δl of the second nanocylindrical cavity 4 will result in different circular dichroism amplitudes and full width at half maximum FWHM. The change of circular dichroism under different Δl values ​​demonstrates the dynamic regulation ability of the chiral response of the metasurface. The data in the figure show that when Δl increases from 0 to 60nm, the circular dichroism value gradually increases from 0 to a high value of 0.99, indicating that the metasurface can achieve a transition from no chirality to strong chirality. When Δl decreases from 0 to -60nm, the circular dichroism value decreases from 0 to -0.87, showing that the metasurface can also achieve a transition from no chirality to strong negative chirality. When Δl is 0nm, the circular dichroism value reaches zero, indicating that the metasurface degenerates into a non-chiral state. These results show that by changing the central axis offset of the second nanocylindrical cavity 4, the chiral response of the metasurface can be precisely controlled to achieve a circular dichroism reversal from negative to positive. In addition, as |Δl| decreases, the FWHM of the circular dichroism spectrum narrows, indicating that the offset of the central axis of the second nanocylindrical cavity 4 also has a significant effect on the width of the circular dichroism spectrum. Figure 4 , select the offset when the circular dichroism amplitude is the largest, that is, the central axis of the second nanocylindrical cavity 4 is offset to the left by 60 nm.

[0040] The asymmetry α affected by the cross-sectional area of ​​the first nanocylindrical cavity 3 and the second nanocylindrical cavity 4 can further regulate the quality factor, but considering the actual processing tolerance problem and the circular dichroism amplitude problem, the cross-sectional radius r of the cylindrical cavity is taken as 25nm. At the same time, the introduction of BIC when the offset Δl is different can be verified by simulation. The calculation formulas for the two are:

[0041]

[0042] Wherein, ΔS is the cross-sectional area of ​​the first nanocylindrical cavity 3 and the second nanocylindrical cavity, S is the sum of the cross-sectional area of ​​the nanoblock 2, the first nanocylindrical cavity 3 and the second nanocylindrical cavity 4, and ω is the complex frequency.

[0043] The performance of the chiral sensor of the present invention can be verified by sensitivity and its excellent value by applying a test analyte in the form of a covering medium to the upper surface of the metasurface, wherein the test analyte has a refractive index n a and thickness t z The left-hand circularly polarized wave and the right-hand circularly polarized wave emitted by the signal generator are vertically irradiated from top to bottom on the chiral sensor covered with the test analyte. The wavelength of the applied electromagnetic wave is λ. The spectrometer receives the transmission wavelength, the refractive index change value Δλ, Δn a Calculate the chiral sensor sensitivity S r , the sensitivity excellence value is further calculated using the sensitivity and the full width at half maximum FWHM of the circular dichroism spectrum:

[0044]

[0045] Among them, γ CD is the full width at half maximum of the circular dichroism spectrum.

[0046] When using the chiral sensor of the present invention to detect the physical change of an object to be detected, the object to be detected is first covered on the upper surface of the metasurface, and the left-handed circularly polarized wave and the right-handed circularly polarized wave emitted by the signal generator are vertically irradiated from top to bottom. The wavelength change value Δλ transmitted by the metasurface structure and the CD curve of the chiral sensor are compared and analyzed by a spectrometer to obtain the physical change of the object to be detected.

[0047] The working principle of the present invention is: by introducing the characteristics of BIC through an asymmetric double cylindrical cavity, by adjusting the radius of the cross-section circle of the asymmetric double cylindrical cavity, the asymmetry of the metasurface changes accordingly, thereby narrowing the full width at half maximum FWHM of the resonance mode and significantly improving the Q factor. Then, the relative position of the offset of the central axis of the second nanocylindrical cavity is adjusted to make the circular dichroism amplitude reach the maximum value, and the circular dichroism value characterizes the responsiveness of the metasurface to chiral molecules. When the offset Δl changes, this change enables the metasurface to distinguish left-handed and right-handed circularly polarized waves with extremely high precision, realizing high-resolution and high-sensitivity sensing of chiral molecules, and providing a new direction for the development of optical sensing technology.

[0048] The following is a description of the technical effects of the present invention in combination with simulation experiments:

[0049] 1. Simulation conditions and contents:

[0050] 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 waves are incident on the all-dielectric metasurface from top to bottom.

[0051] Simulation 1, the relationship between the Q factor and the asymmetry α of the present invention is simulated under different conditions of the offset Δl of the central axis of the second nanocylindrical cavity. The simulation results are as follows: Figure 5 shown.

[0052] Simulation 2 is a simulation of the normalized electric field distribution of the specific embodiment of the present invention. The simulation result is shown in FIG6 .

[0053] Simulation 3 compares the transmission response component of the specific embodiment of the present invention with the time coupled mode theory fitting component, and the result is shown in FIG7 .

[0054] Simulation 4 simulates the chiral sensing sensitivity and excellent value of the specific embodiment of the present invention, and the simulation results are shown in FIG8 .

[0055] 2. Analysis of simulation results:

[0056] Reference Figure 5, showing the change of Q factor under different asymmetry degrees α, revealing the significant influence of the offset Δl of the central axis of the second nanocylindrical cavity on the performance of the metasurface. The simulation results show that with the increase of α, the Q factor presents a specific change trend. When α is 0, it shows an infinite Q factor, which helps to achieve ultra-narrow resonance linewidth and extremely high sensing accuracy. Under the conditions of Δl of 15nm, 60nm and 75nm, ultra-high Q factors are shown, which means that its resonance mode has extremely high quality, which is crucial for improving the sensitivity and selectivity of the sensor, indicating that Δl can flexibly adjust the resonance characteristics of the metasurface. These results prove that by adjusting the relative position of the offset of the central axis of the second nanocylindrical cavity, the chiral sensing performance of the metasurface can be effectively optimized, providing important guidance for the design of high-performance chiral sensors.

[0057] Referring to Figure 6, the near-field analysis results of the all-dielectric metasurface proposed in the specific embodiment are shown. The simulation results show the normalized electric field under the irradiation of left-handed circularly polarized waves and right-handed circularly polarized waves. Distribution on the xy plane. It can be observed that left-handed circularly polarized waves and right-handed circularly polarized waves excite electric quadrupole modes. In this embodiment, the electric field is enhanced by 22 times under the irradiation of left-handed circularly polarized waves, while it is enhanced by 141 times under the irradiation of right-handed circularly polarized waves, and the circular dichroism value is 0.99. These results provide strong evidence for the realization of high-precision chiral sensing.

[0058] 7, a comparison diagram of the transmission coefficient components and the coupled mode theory CMT fitting results in a specific embodiment is shown, where (a) is T ll ; (b) is the cross component T lr =T rl , (c) is T rr . . The calculation formula of the transmission coefficient component is:

[0059]

[0060] Where γ0 is the emissivity, l represents the left-hand circular polarization state, r represents the right-hand circular polarization state, and A k , B k , C k and D k is a real number, recording the non-chiral scattered field and the coupling between the proposed metasurface and the incident. The figure plots the components of the transmission coefficient in detail, as well as the corresponding coupled mode theoretical fitting line. When Δl is 60nm, it can be seen from Figure 7 that the cross component T lr =T rl It is strongly suppressed in this metasurface and can be ignored. The T ll exceeds 0.985, and T rrClose to zero, which leads to the maximum circular dichroism value reaching 0.99. The high consistency between the coupled mode theory fitting line and the simulation results further confirms the accuracy of the model and provides a reliable theoretical basis for understanding and predicting the chiral response of metasurfaces.

[0061] Referring to FIG8(a), the sensitivity performance of the all-dielectric metasurface in the chiral sensing application proposed in the specific embodiment is shown. The simulation results show that the different thicknesses of the test samples have a significant effect on the sensitivity. As the thickness of the sample increases, the increase in sensitivity tends to be flat. In particular, at t z When the wavelength is 300nm, the sensitivity reaches 172.7nm / RIU, which shows the high efficiency of the metasurface in detecting the change of the refractive index of the sample. These results demonstrate the potential application of metasurfaces in the field of biosensing, especially in detection scenarios that require high sensitivity and high resolution.

[0062] Referring to FIG8( b ), the excellent sensitivity of the all-dielectric metasurface proposed in the specific embodiment in the chiral sensing application is shown. The simulation results show that at a thickness of t z When the wavelength is 300nm and the sensitivity is 172.7nm / RIU, the chiral response excellence value of the metasurface reaches 7.51×10 4 RIU -1 This significant improvement means that the metasurface has higher sensitivity and resolution in chiral sensing and can detect chiral molecules more effectively.

[0063] The above description is only a preferred embodiment of the present invention and does not constitute a limitation to the present invention. A person skilled in the art may make several modifications and improvements without departing from the innovative concept of the present invention, but these changes shall all fall within the scope of protection of the present invention.

Claims

1. A BIC-based all-dielectric metasurface chiral sensor, comprising a metasurface structure composed of a plurality of periodically arranged all-dielectric metasurface units, a signal generator and a spectrometer; the all-dielectric metasurface unit comprises a nano-substrate (1) and a nano-block (2) fixed on its upper surface; characterized in that: The nanoblock (2) adopts a tetrahedral structure with a square cross section, and is provided with a first nanocylindrical cavity (3) and a second nanocylindrical cavity (4) which penetrate the upper and lower surfaces and are asymmetric with respect to the central axis of the nanoblock (2), and are used to realize the continuum bound state BIC characteristics, wherein the central axis of the first nanocylindrical cavity (3) is located on a diagonal plane of the nanoblock (2), and the central axis of the second nanocylindrical cavity (4) is located at a position offset from the diagonal plane, and the offset Δl and the offset direction are determined by the maximum amplitude of the circular dichroism CD.

2. The all-dielectric metasurface chiral sensor according to claim 1, characterized in that: The nano substrate (1) is a silicon dioxide plate having a square surface shape.

3. The all-dielectric metasurface chiral sensor according to claim 2, characterized in that: The nano block (2) is made of semiconductor material such as silicon, silicon nitride or gallium arsenide.

4. The all-dielectric metasurface chiral sensor according to claim 3, characterized in that: The center normal line of the nano block (2) coincides with the center normal line of the nano substrate (1).

5. The all-dielectric metasurface chiral sensor according to claim 1, characterized in that: The central axis of the second nano-cylindrical cavity (4) is parallel to the central axis of the first nano-cylindrical cavity (3).

6. The all-dielectric metasurface chiral sensor according to claim 5, characterized in that: The central axes of the first nano-cylindrical cavity (3) and the second nano-cylindrical cavity (4) are parallel to the central normal line of the nano-base (1).

7. The all-dielectric metasurface chiral sensor according to claim 1, characterized in that: The maximum amplitude of the circular dichroism CD refers to the maximum value of the circular dichroism CD calculated by the spectrometer through the transmittance of the left-hand circularly polarized wave transmitted by the left-hand circularly polarized wave and the right-hand circularly polarized wave converted therefrom, and the right-hand circularly polarized wave transmitted by the right-hand circularly polarized wave and the left-hand circularly polarized wave converted therefrom, when the left-hand circularly polarized wave and the right-hand circularly polarized wave are vertically irradiated from top to bottom by the signal generator, wherein the calculation formula of CD is: Among them, T l , T r They represent the total transmittance of the transmitted left-hand circularly polarized wave and right-hand circularly polarized wave respectively.

8. The all-dielectric metasurface chiral sensor according to claim 1, characterized in that: The quality factor Q of the continuum bound state BIC is calculated by regulating the asymmetry α through the cross-sectional areas of the first nanocylindrical cavity (3) and the second nanocylindrical cavity (4), wherein the calculation formulas of α and Q are respectively: Wherein, ΔS is the sum of the cross-sectional areas of the first nanocylindrical cavity and the second nanocylindrical cavity, S is the cross-sectional area of ​​the nanoblock, ω is the complex frequency, r is the radius of the first nanocylindrical cavity and the second nanocylindrical cavity, l is the side length of the cross-sectional area of ​​the nanoblock, and Re() and Im(·) are the real and imaginary part operations, respectively.

9. An all-dielectric metasurface chiral sensor according to any one of claims 1 to 8, characterized in that: When detecting the physical change of the object to be detected, the object to be detected is first covered on the upper surface of the metasurface, and the left-handed circularly polarized wave and the right-handed circularly polarized wave emitted by the signal generator are vertically irradiated from top to bottom. The wavelength change value Δλ transmitted by the metasurface structure and the CD curve of the chiral sensor are compared and analyzed by a spectrometer to obtain the physical change of the object to be detected.

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