CN114577753A - High-Q Refractive Index Sensor Based on Quasi-Continuous Domain Bound State and Its Fabrication Method - Google Patents

Abstract

The invention relates to the technical field of metamaterials, in particular to a high-Q-value refractive index sensor based on a quasi-continuous domain bound state and a preparation method thereof. The all-dielectric super-surface structure array is formed by periodically arranging a plurality of all-dielectric super-surface units, each all-dielectric super-surface unit is a square block structure, a notch is formed in one side face of each square block structure along the x direction, the position, the orientation, the shape and the size of each notch formed in each square block structure are identical, and the all-dielectric super-surface unit provided with the notch is used for exciting magnetic dipole moment along the z direction when plane waves polarized along the x direction are normally incident to form a bound state in a quasi-continuous domain and forming a resonant cavity with a high Q value by utilizing the bound state in the quasi-continuous domain. According to the invention, the symmetry of the structure in the x direction is broken, so that the continuous domain bound state is converted into the quasi-continuous domain bound state, a very high Q value is obtained, and the sensing performance of the refractive index sensor is improved to a great extent.

Description

High-Q Refractive Index Sensor Based on Quasi-Continuous Domain Bound State and Its Fabrication Method

technical field

The invention relates to the technical field of metamaterials, in particular to a high-Q-value refractive index sensor based on a quasi-continuous domain bound state and a preparation method thereof.

Background technique

Metasurfaces point a new direction for the miniaturization of optical devices. A metasurface is a two-dimensional nanometer metamaterial, which is generally composed of subwavelength artificial unit structures. By artificially designing the unit structures and their arrangement, structures that are different from the properties of natural materials can be fabricated. At present, metasurfaces can usually be divided into metal metasurfaces based on surface plasmons and all-dielectric metasurfaces based on Mie resonance, which can be used in refractive index sensing, optical imaging, high-order harmonic generation and other fields.

Sensitivity and quality factor are the two key indicators of refractive index sensors. The Q value is used to measure the width of the resonant spectral line. When the sensitivity is constant, the higher the Q value of the resonant spectral line, the higher the quality factor of the refractive index sensor. Due to the ohmic loss of metal materials, the Q value of the resonant spectral linewidth is usually low, which limits its application in refractive index sensors. The refractive index sensor based on dielectric materials replaces the ohmic current with displacement current, which reduces the ohmic loss and improves the Q value of the resonant spectral line. Dielectric materials can also excite modes such as magnetic resonance, ring-pair resonance, and high-order resonance in addition to electrical resonance. Enhanced refractive index sensing performance.

Bound-States-in-the-Continuum (BIC) in the continuum domain is a mode whose resonant frequency is located in the radiation continuum domain, but is completely decoupled from the radiation state, also known as trapped mode. ). Theoretically, the Q value of the resonance excited by BIC is infinite and the resonance linewidth is 0, but it can only exist in a lossless infinite structure and cannot be used in practical refractive index sensing experiments. In reality, the resonance excited by the BIC still has a certain radiation loss, which limits the further improvement of the resonance Q value, resulting in an unsatisfactory sensing performance of the refractive index sensor.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a high-Q refractive index sensor based on the bound state of the quasi-continuous domain and a preparation method thereof, aiming at the defects of the prior art. The bound state (quasi-BIC, QBIC) in , so as to obtain an extremely high Q value, which greatly improves the sensing performance of the refractive index sensor.

The present invention provides a high-Q refractive index sensor based on a quasi-continuous domain bound state. The all-dielectric metasurface units are periodically arranged to form, and the all-dielectric metasurface unit is a square block structure, the square block structure is provided with a gap on one side along the x direction, and the position of the gap set on each square block structure is , the orientation, shape and size are all the same, and the all-dielectric metasurface unit with the gap is used to excite the magnetic dipole moment along the z-direction when the plane wave polarized along the x-direction is normal incident, forming a confinement in the quasi-continuous domain state, and use the bound state in the quasi-continuous domain to form a high-Q resonant cavity;

The x direction is the length direction of the base layer, the y direction is the width direction of the base layer, and the z direction is the height direction of the base layer.

More preferably, each of the square block structures is provided with only one notch, and the notch is an arc-shaped notch, and the arc-shaped surface of the arc-shaped notch is perpendicular to the upper surface of the square block structure.

More preferably, the diameter of the circle where the arc-shaped notch is located is not less than the length of the square block structure along the x direction.

More preferably, the following relationship is satisfied between the arc-shaped gap and the square block structure:

Among them, h is the vertical distance from the center of the circle where the arc-shaped gap is located to the x-direction centerline of the square block structure, r is the radius of the circle where the arc-shaped gap is located, and a is the x-direction length of the square block structure.

More preferably, the arc-shaped surface is tangent to both side surfaces of the square block structure along the y-direction.

More preferably, the arrangement period of the all-dielectric metasurface units along the x-direction and the y-direction is equal, and the arrangement period is 7/20*a～5/7*a, where a is the all-dielectric metasurface unit along the x direction. the length of the direction.

More preferably, the arrangement period of the all-dielectric metasurface unit along the x direction and the y direction is 700nm-1000nm, the length a of the all-dielectric metasurface unit along the x direction is 350-500nm, and the radius of the circle where the arc-shaped surface is located is 175-260nm.

The solution also provides a preparation method of a high-Q refractive index sensor based on a quasi-continuous domain bound state, comprising:

A layer of photoresist is evenly plated on the quartz substrate;

A pattern of all-dielectric metasurface units is drawn on the photoresist using electron beam exposure, the pattern is distributed in a periodic array on the surface of the photoresist, and the pattern is a square with a gap, and the gap is located in a square On one side edge along the x direction, the gap is an arc gap;

Dissolve the patterned sample in a preconfigured developer solution, so that a cavity is formed on the photoresist where the pattern is drawn;

depositing a silicon thin film with a specified thickness in the cavity by chemical vapor deposition;

The photoresist is removed to form a high-Q refractive index sensor based on a quasi-continuous domain bound state, and the high-Q refractive index sensor based on a quasi-continuous domain bound state can be excited when a plane wave polarized along the x-direction is normally incident. The magnetic dipole moment along the z-direction forms bound states in a quasi-continuous domain, and uses the bound states in the quasi-continuous domain to form a high-Q resonant cavity.

The beneficial effect of the present invention is that the symmetry of the structure of the metasurface unit is broken by introducing a notch in the x-direction of the all-dielectric metasurface unit of the square block. When a plane wave polarized in the x-direction is incident normally, a magnetic dipole moment in the z-direction is excited, and its resonant mode is an even mode that is rotated 180° around the z-axis, due to the odd mode excited by the plane wave propagating in the z-direction Mismatched, the two modes do not couple, resulting in a QBIC, which manifests as a Fano resonance line in the transmission line. The invention utilizes the QBIC to generate a resonant cavity with a high Q value, and brings about a strong local field enhancement, and is applied in the field of refractive index sensing to achieve an ultra-high quality factor. The invention has simple structural design and easy processing, and has important applications in the fields of chemical biosensing and the like.

Description of drawings

1 is a schematic structural diagram of a high-Q refractive index sensor based on a quasi-continuous domain bound state of the present invention;

Fig. 2 is the structural schematic diagram when the all-dielectric metasurface unit of the present invention is a square block;

3 is a top view when the all-dielectric metasurface unit of the present invention is a square block;

Fig. 4 is the transmission spectrum of the square silicon block and the square silicon block with the arc-shaped notch under the condition of the same side length;

5 is a schematic diagram of the current distribution of the xy cross-section when the thickness at the resonance wavelength is half the height of the structure;

Figure 6. Multipole decomposition result diagram of scattered energy;

Fig. 7 Electromagnetic field distribution diagram of different notch structures under the same broken area at the resonance wavelength;

Fig. 8 is a graph of the change of the transmission spectrum with the refractive index;

Fig. 9 is a graph of the relationship between the resonance wavelength and the refractive index change of the surrounding medium;

Fig. 10 is a top view when the all-dielectric metasurface unit of the present invention is a rectangular block;

In the figure: 1-Base layer, 2-All-dielectric metasurface unit, 3-Notch, 4-All-dielectric metasurface structure array, 5-Arc surface

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

It is to be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top" , "bottom", "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, which are only for the convenience of describing the application and simplifying the description, rather than indicating or implying the indicated device. Or elements must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as a limitation of the present application.

In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present application, "plurality" means two or more, unless otherwise expressly and specifically defined.

A high-Q refractive index sensor based on a quasi-continuous domain bound state of the present invention includes a base layer 1 and an all-dielectric metasurface structure array 4 located on the base layer 1. The all-dielectric metasurface structure array 4 is composed of several all-dielectric metasurface structures. The surface units 2 are periodically arranged and formed. The all-dielectric metasurface unit 2 is a square block structure. The square block structure is provided with a gap 3 on one side along the x direction. The position, orientation and shape of the gap 3 set on each square block structure The all-dielectric metasurface unit 2 with the gap 3 is used to excite the magnetic dipole moment along the z-direction when the plane wave polarized along the x-direction is normal incident, forming bound states in the quasi-continuous domain, and using The bound states in the quasi-continuous domain form high-Q resonators;

Among them, the x direction is the length direction of the base layer 1, the y direction is the width direction of the base layer 1, and the z direction is the height direction of the base layer 1. The square block structure of this scheme has the side length a along the x direction and the side length b along the y direction. It can be equal, that is, the square block structure is a square block; or the side length a and the side length b are not equal, that is, the square block structure is a rectangular block.

The notch 3 may be multiple or single, and the shape of the notch may be a square, a V-shaped, a U-shaped, an arc, or the like.

This scheme utilizes the break of structural symmetry to convert the BIC mode with basically no radiation and infinite Q value to the QBIC mode with lower radiation and larger Q value, and excites the resonance mode that cannot be excited by the incident light at the resonance wavelength. , its resonance line width is extremely narrow and accompanied by the phenomenon of localized electric field enhancement, so it has great practical significance in the development of optical sensing devices.

Example 1

1 and 2 show a schematic structural diagram of a high-Q refractive index sensor based on a quasi-continuous domain bound state provided by an embodiment of the present application. The square block structure selected in this embodiment is a square block. For the convenience of description, Only the parts related to this embodiment are shown, and the details are as follows:

In this embodiment, each square block structure is provided with only one notch 3, and the notch 3 is an arc-shaped notch, and the arc-shaped surface 5 of the arc-shaped notch is perpendicular to the upper surface of the square block structure.

The diameter of the circle where the arc-shaped notch is located is not less than the length of the square block structure along the x direction.

The following relationship is satisfied between the arc notch and the square block structure:

Among them, h is the vertical distance from the center of the circle where the arc-shaped gap is located to the x-direction centerline of the square block structure (also the distance between the center of the circle and the center of the square block), r is the radius of the circle where the arc-shaped gap is located, and a is the x of the square block structure to length.

所以弧形面5底部始终不低于正方形的中心点。As shown in FIG. 3 , when h takes a value in the range satisfying the expression, the arc-shaped surface 5 is always tangent or intersecting with both sides of the square block structure along the y-direction. According to the expression, the center of the circle corresponding to the arc-shaped surface 5 can be located either outside the square body or on the side of the square body, but should not be located inside the square body. At the same time due to

Therefore, the bottom of the arc surface 5 is always not lower than the center point of the square.

The arrangement period of the all-dielectric metasurface unit 2 along the x-direction and the y-direction is equal, and the arrangement period is 7/20*a～5/7*a, where a is the length of the all-dielectric metasurface unit 2 along the x-direction.

More preferably, the arrangement period of the all-dielectric metasurface unit 2 along the x-direction and the y-direction is 700nm-1000nm, the length a of the all-dielectric metasurface unit 2 along the x-direction is 350-500nm, and the radius of the circle where the arcuate surface 5 is located. is 175-260 nm, and the height of the all-dielectric metasurface unit 2 along the z-direction is 20-60 nm.

Compared with the gaps of other shapes such as triangles and square gaps, the introduction of arc-shaped gaps inside the square metasurface structure can maximize the localization ability of the electromagnetic field, and can expand the scope of local electromagnetic field enhancement. Thus, it is more beneficial to improve the sensing performance.

Embodiment 2

This embodiment provides a method for fabricating a high-Q refractive index sensor based on a quasi-continuous domain bound state, comprising:

A layer of photoresist is evenly plated on the quartz substrate, and the photoresist is positive photoresist;

The pattern of the all-dielectric metasurface unit 2 is drawn on the photoresist using the electron beam exposure method. The pattern is distributed in a periodic array on the surface of the photoresist, and the pattern is a square with a notch 3. On the side, the gap 3 is an arc gap;

Dissolve the patterned sample in a preconfigured developer solution, so that a cavity is formed on the photoresist where the pattern is drawn;

A silicon thin film of a specified thickness is deposited in the cavity by chemical vapor deposition;

The photoresist is removed to form a high-Q refractive index sensor based on the quasi-continuous bound state. The high-Q refractive index sensor based on the quasi-continuous bound state can excite the z-direction when the plane wave polarized along the x-direction is normal incident. The magnetic dipole moment forms the bound state in the quasi-continuous domain, and uses the bound state in the quasi-continuous domain to form a high-Q resonator.

Embodiment 3

This embodiment provides another method for fabricating a high-Q refractive index sensor based on a quasi-continuous domain bound state, comprising:

A silicon film of a fixed thickness is deposited on a quartz substrate using chemical vapor deposition;

The photoresist is evenly plated on the silicon film;

The pattern of the all-dielectric metasurface unit was drawn on the photoresist using the electron beam exposure method. The pattern is distributed in a periodic array on the surface layer of the photoresist. The pattern is a square with a gap, and the gap is located on one side of the square along the x direction. , the gap is an arc gap;

Place the patterned sample in a pre-configured developer solution to dissolve the rest of the photoresist except for the pattern;

The surface of the sample is etched by reactive ion etching to form a high-Q refractive index sensor based on the quasi-continuum bound state. At normal incidence, the magnetic dipole moment along the z-direction is excited, forming bound states in the quasi-continuous domain, and using the bound states in the quasi-continuous domain to form high-Q resonators.

In the preparation method, the photoresist is a negative photoresist, specifically a polymethyl methacrylate photoresist. Before depositing the silicon film, it also includes placing the quartz substrate in an ultrasonic cleaner for cleaning, and cleaning the quartz substrate with deionized water after the ultrasonication, and finally blowing it with an air gun.

In this embodiment, a silicon film is deposited first, and then a negative photoresist is used to develop and etch. Compared with another embodiment, the method of first using a positive photoresist to develop the cavity, and then depositing the filled silicon film has the following advantages: Advantage:

1. Selecting a negative photoresist such as polymethyl methacrylate (PMMA) can make the new substances generated by the breaking of the molecular bonds of the exposed photoresist easier to dissolve during the electron beam exposure process, which is conducive to the production of more A clear pattern, the all-dielectric metasurface unit formed by etching on the basis of a clearer pattern has a smoother boundary, so that the performance of the sensor is better.

2. Due to the large area of the metasurface array to be prepared, a silicon film is deposited first, and then developed and etched with a negative photoresist. method that consumes less material.

Embodiment 4

In this embodiment, the performance of the sensor of the present invention is analyzed and explained in combination with specific value parameters. The values in this embodiment are: the size of the arrangement period P is 900 nm, the side length a of the square block is 450 nm; the radius r corresponding to the arc-shaped gap is 230 nm; the distance h between the center of the circle corresponding to the arc-shaped gap and the center of the unit is 190nm; the height of the square block structure is 30nm.

This embodiment uses the finite element method to simulate the interaction between incident electromagnetic waves and all-dielectric metasurface structure arrays. In the simulation calculation process, the x-axis direction and the y-axis direction are set as periodic boundary conditions, the z-axis direction, that is, the height direction of the base layer, is set as the perfect matching layer, and the surrounding material of the all-dielectric metasurface unit (in the actual application process, through Liquids with different refractive indices were dropped on the all-dielectric metasurface unit structure to measure the sensing performance of the refractive index (the refractive index n=1.45), and the incident electromagnetic wave was set as a plane wave polarized in the x-direction, incident along the negative direction of the z-axis.

The transmission spectrum of the normal incident plane wave is calculated by the setting of the above simulation conditions, and the result is shown in Fig. 4. When the radius of the arc-shaped gap is 0, that is, the all-dielectric metasurface is composed of square blocks, the transmittance is basically 1 in the 1307-1309 nm band. When the arc-shaped gap is introduced and the radius is 230 nm, the wavelength of the transmission spectrum can be A very narrow Fano resonance peak is found at 1307.5nm, and its Q value can reach 130752.

In order to understand the formation reasons of QBIC more clearly, the displacement current distribution on the xy cross-section of the all-dielectric metasurface unit at the resonance wavelength is calculated, as shown in Fig. 5. In Figure 5, the direction of the arrow represents the direction of the current, the length of the arrow represents the magnitude of the current at the point, and the gray scale represents the magnitude of the electric field intensity. In the xy section, the displacement current exhibits a vortex shape, which induces a magnetic dipole moment in the z direction, which does not match the odd mode excited by the plane wave propagating in the z direction, and does not occur between the two modes. The coupling, thereby forming a QBIC, appears as a Fano resonance line in the transmission line of the incident light. The formation of the QBIC traps most of the energy around the structure, resulting in a transmittance minimum close to zero.

The multipole energy decomposition results in the Cartesian coordinate system are shown in Figure 6, and the scattered power of each resonance can be observed more clearly, where I _p represents the scattered energy of the electric dipole, and I _m represents the scattering of the magnetic dipole. The energy, I _t represents the scattered energy of the ring dipole, I _Qe the scattered energy of the electric quadrupole, and I _Qm the scattered energy of the magnetic quadrupole. It can be seen from Fig. 6 that at the resonance wavelength, the scattering power of the magnetic dipole dominates, which is consistent with the analysis result in Fig. 5. At the same time, we can observe that the scattering power of the electric quadrupole is almost equal to that of the magnetic dipole. This is because the current surrounding the interior of the metasurface structure also forms two pairs of opposite currents at the resonance wavelength, which is exactly the same as the electric current. Characteristics of a quadrupole.

At the same time, in order to find out the notch shape and the number of notch with the best electric field gain effect, we carried out a lot of experiments on the combination of different numbers and notch shapes, and finally obtained the optimal notch as a single notch and an arc-shaped notch. It is verified by taking three different shapes of triangle, square and circular arc in a single gap, and the area occupied by all gaps is almost equal, and the results are shown in Figure 7. Compared with the other two shapes of the arc notch, we can find that the local electric field energy of the arc notch is the strongest by comparing the color map; in addition, compared with the square notch, the triangular and circular arc notch can enlarge the local area Compared with the triangular notch, the arc-shaped notch has the best local electric field capability, which can greatly improve the performance of the refractive index sensing.

通过计算透射谱的平均半高全宽(Full Width at Half Maximum,FWHM)为0.01nm，可以计算出折射率传感的品质因数

This all-dielectric metasurface, which can generate high Q value, is applied in the field of refractive index sensing. By changing the refractive index of the surrounding environment of the structure, the shift of the resonance wavelength is observed, and the ratio of the two is used to calculate the refractive index transfer of the structure. Sensitivity (S) and figure of merit (FOM) of the sense. Specifically, the calculation results of the sensing performance of the structure are shown in Figures 8 and 9. By calculating the resonance wavelength shift Δλ of the transmission spectrum and the refractive index change Δn, the sensitivity of the refractive index sensing can be calculated.

By calculating the average full width at half maximum (FWHM) of the transmission spectrum to be 0.01 nm, the quality factor of the refractive index sensor can be calculated

In summary, the present invention achieves a very narrow Fano spectral line with a Q value of 130752 by introducing a circular arc-shaped notch in a square silicon block, and finally achieves a sensitivity of 434 by changing the refractive index of the surrounding environment of the all-dielectric metasurface, Sensing performance with a figure of merit of 43400. The invention has the characteristics of easy preparation, small volume and high quality factor, and has a very broad application prospect in the field of biological sensing.

Embodiment 5

FIG. 10 shows another embodiment of the present invention for illustration. The square block structure selected in this embodiment is a rectangular block, and the rectangular block satisfies that the side length a along the x direction is greater than the side length b along the y direction.

In the process of parameter optimization, we found that if the side length of the bottommost side of the square metasurface is a fixed value a (that is, the side length along the x direction is a), then through the calculation of the geometric relationship, we can get the asymmetry The factor α=arc broken area/(a*a), the asymmetry factor α will gradually increase with the increase of the broken area, that is, the smaller the remaining area, the higher the Q value of the resonant cavity. Therefore, when the center of the arc corresponding to the circle is located inside the square whose side length is a, the Q value of the resonant cavity is higher. When the center of the arc corresponding to the circle is located inside the square with the side length a, the gap is filled, the geometric structure will form a rectangle, and the side length a of the rectangular block along the x direction is greater than the side length b along the y direction. Its geometric structure can be shown in Fig. 10. Compared with the square structure, introducing a notch in the rectangular structure as shown in the figure can obtain a resonant cavity with a high Q factor.

It should be understood that the size of the sequence numbers of the steps in the above embodiments does not mean the sequence of execution, and the execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

The above-mentioned embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the above-mentioned embodiments, those of ordinary skill in the art should understand that the above-mentioned implementations can still be used. The technical solutions recorded in the examples are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions in the embodiments of the application, and should be included in the within the scope of protection of this application.

Claims (8)

1. A high-Q refractive index sensor based on a quasi-continuous domain bound state, characterized in that it comprises a base layer (1) and an all-dielectric metasurface structure array (4) located on the base layer (1), The dielectric metasurface structure array (4) is formed by periodically arranging a plurality of all-dielectric metasurface units (2), and the all-dielectric metasurface unit (2) is a square block structure, and the square block structure is in a direction along the x direction. A gap (3) is provided on the side surface, the position, orientation, shape and size of the gap (3) provided on each square block structure are the same, and the all-dielectric metasurface unit (2) provided with the gap (3) is used for When the plane wave polarized along the x-direction is normally incident, the magnetic dipole moment along the z-direction is excited to form a bound state in a quasi-continuous domain, and a high-Q resonator is formed by using the bound state in the quasi-continuous domain; Wherein, the x direction is the length direction of the base layer (1), the y direction is the width direction of the base layer (1), and the z direction is the height direction of the base layer (1). 2. The high-Q-value refractive index sensor based on quasi-continuous domain bound state according to claim 1, characterized in that: each of the square block structures is provided with only one gap (3), and the gap (3) is An arc-shaped gap, the arc-shaped surface (5) of the arc-shaped gap is perpendicular to the upper surface of the square block structure. 3 . The high-Q refractive index sensor based on the quasi-continuous domain bound state according to claim 2 , wherein the diameter of the circle where the arc-shaped gap is located is not less than the length of the square block structure along the x direction. 4 . 4. The high-Q-value refractive index sensor based on the quasi-continuous domain bound state according to claim 2, wherein the arc-shaped gap and the square block structure satisfy the following relationship:

Among them, h is the vertical distance from the center of the circle where the arc-shaped gap is located to the x-direction centerline of the square block structure, r is the radius of the circle where the arc-shaped gap is located, and a is the x-direction length of the square block structure. 5 . The high-Q refractive index sensor based on quasi-continuous domain bound state according to claim 2 , wherein the arc-shaped surface ( 5 ) is tangent to both sides of the square block structure along the y-direction. 6 . 6. The high-Q-value refractive index sensor based on the quasi-continuous domain bound state according to claim 2, characterized in that: the all-dielectric metasurface units (2) have equal periods of arrangement along the x-direction and the y-direction, so The arrangement period is 7/20*a～5/7*a, and a is the length of the all-dielectric metasurface unit (2) along the x direction. 7. The high-Q-value refractive index sensor based on quasi-continuous domain bound state according to claim 6, characterized in that: the arrangement period of the all-dielectric metasurface unit (2) along the x-direction and the y-direction is 700nm- 1000 nm, the length a of the all-dielectric metasurface unit (2) along the x direction is 350-500 nm, and the radius of the circle where the arc-shaped surface (5) is located is 175-260 nm. 8. A method for preparing a high-Q refractive index sensor based on a quasi-continuous domain bound state, characterized in that: comprising: A layer of photoresist is evenly plated on the quartz substrate; A pattern of all-dielectric metasurface units (2) is drawn on the photoresist using an electron beam exposure method, the pattern is distributed in a periodic array on the surface of the photoresist, and the pattern is a square with a gap (3) , the gap (3) is located on one side of the square along the x direction, and the gap (3) is an arc gap; Dissolve the patterned sample in a pre-configured developer solution, so that a cavity is formed on the photoresist where the pattern is drawn; depositing a silicon thin film with a specified thickness in the cavity by chemical vapor deposition; The photoresist is removed to form a high-Q-value refractive index sensor based on a quasi-continuous domain bound state, and the high-Q-value refractive index sensor based on a quasi-continuous domain bound state can be excited when a plane wave polarized along the x-direction is normally incident. The magnetic dipole moment along the z-direction forms bound states in a quasi-continuous domain, and uses the bound states in the quasi-continuous domain to form a high-Q resonant cavity.

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