Multi-polymer dual-band refractive index sensor based on continuous domain bound state and manufacturing method of multi-polymer dual-band refractive index sensor

Abstract

The invention discloses a polymer dual-band refractive index sensor based on a continuous domain bound state and a manufacturing method of the polymer dual-band refractive index sensor. The sensor comprises a silicon dioxide substrate and polymer metasurface structure units distributed on the upper surface of the silicon dioxide substrate in an array mode. Each polymer metasurface structure unit comprises four positive polygonal cylinders and a cylinder, the four positive polygonal cylinders are identical in size, the positive polygonal cylinders and the cylinder are perpendicular to the silicon dioxide substrate, the positive polygonal cylinders are arranged in a matrix mode, and the cylinder is located in the center of the four positive polygonal cylinders. The introduction of the central cylinder not only breaks the structural symmetry to excite the quasi-BIC, but also enhances the coupling effect among the four straight square columns, thereby greatly improving the near-field enhancement effect. The refractive index sensor has the characteristics of double quasi-BIC sensing wavebands, high sensitivity, high Q value, polarization insensitivity and the like, and the detection efficiency, flexibility and accuracy of the refractive index sensor in the biomedical field are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical devices, and in particular to a polymer dual-band refractive index sensor based on a continuous domain bound state and a manufacturing method thereof. Background Art

[0002] As a powerful means to enhance the interaction between light and matter, optical metasurfaces are artificial materials composed of two-dimensional periodic subwavelength structure arrays. Their ability to flexibly adjust the amplitude, phase and polarization state of incident light at the micro-nano scale has attracted extensive research and attention in recent years. On the one hand, the nanomaterials that make up the optical metasurface have the characteristics of high strength, hardness, conductivity, thermal stability and optical activity. On the other hand, the preparation of optical metasurfaces is highly controllable. Specifically, the size, structure and composition of the optical metasurface can be precisely controlled through different synthesis techniques. This adjustability enables optical metasurfaces to meet the needs of specific applications. In addition, the properties of metasurfaces composed of different materials are quite different. Generally speaking, metal metasurfaces have superior sensitivity, but due to the inherent loss of the material, the quality factor is usually low. Especially in the near-infrared and visible light bands, the large ohmic loss of metal metasurfaces will further cause heating of the device, thereby seriously affecting the efficiency and stability of detection; dielectric materials produce sharp resonances due to smaller material losses, and usually have a quality factor that is more than two orders of magnitude higher than the former. Finally, the increasingly mature micro-nano component preparation technologies (such as electron beam lithography, laser direct writing lithography, nanoimprint technology, laser ablation, etc.) provide a good processing and production approach for the research and application of optical metasurfaces.

[0003] In the radiation continuum, the bound continuum state (BIC) is a type of electromagnetic eigenstate that does not radiate. Although its frequency and momentum may match the vacuum mode, it is still completely bound in the resonant system and does not radiate any energy outward. It is a perfect bound state. The bound continuum state has an infinite quality factor. However, optical BIC is an ideal state because it is impossible to have an infinite periodic system. In fact, its radiation leakage mode is mainly used: quasi-BIC. By adjusting parameters such as system configuration, size, periodic boundary or excitation wave vector, BIC can be weakly coupled with the far field, so that a small part leaks into the surrounding environment. This state is called quasi-BIC. The radiation loss of the BIC-based system can be precisely controlled by adjusting the interference of the constituent resonant modes, thereby obtaining quasi-BICs with different leakage degrees. Studies have shown that the quality factor (Q value) of quasi-BIC is inversely proportional to the square of the structural perturbation, that is, the realization of high Q value is often accompanied by weak structural perturbations, which poses a huge challenge to actual processing and manufacturing, limiting the practical application of quasi-BIC metasurfaces.

[0004] Refractive index is an inherent property of materials, and it is of great significance to detect refractive index to identify different substances. The dielectric metasurface based on continuous domain bound state is very sensitive to the change of refractive index of the surrounding environment, and can be applied to the field of sensing. It can achieve fast and non-destructive sensing without labeling, thereby indirectly analyzing the qualitative and quantitative aspects of the material. This type of metasurface can achieve better sensing performance due to its narrower line width and stronger near-field enhancement effect. It is convenient and flexible, with high detection efficiency, and can be used in agriculture, biomedicine, environmental monitoring, food testing, chemical industry and other fields.

[0005] Existing dielectric metasurfaces based on continuous domain bound states usually do not have the advantages of multi-resonance sensing and high sensitivity. Multi-resonance sensing can significantly reduce the errors caused by environmental fluctuations and expand the detection range of refractive index changes, thereby more effectively detecting the information of the substance to be tested. High sensitivity can more accurately detect environmental changes and improve the accuracy of detection. Summary of the invention

[0006] The purpose of the present invention is to solve the defects of the above-mentioned existing technologies and propose a polymer dual-band refractive index sensor based on continuous domain bound state and a method for manufacturing the same, which has the characteristics of dual channels, high sensitivity, high Q value, robustness, customizability, polarization insensitivity, etc.

[0007] The technical solution for achieving the purpose of the present invention is: a polymer dual-band refractive index sensor based on continuous domain bound states, comprising a silica substrate and a polymer supersurface structure unit arrayed on the upper surface of the silica substrate, wherein the polymer supersurface structure unit comprises four regular even polygonal cylinders of exactly the same size and one cylinder, wherein the regular even polygonal cylinders and the cylinder are perpendicular to the silica substrate, the regular even polygonal cylinders are arranged in a matrix, and the cylinder is located at the center of the four regular even polygonal cylinders.

[0008] Preferably, the regular even polygonal column is a rectangular column.

[0009] Preferably, the rectangular column and the circular cylinder have the same height.

[0010] Preferably, the height of the rectangular column and the circular column is equal to the thickness of the silicon dioxide substrate.

[0011] Preferably, the bottom surfaces of the four rectangular columns are squares with a side length of a, and the centers of the four rectangular columns are respectively located at one quarter of the polymer supersurface structure unit.

[0012] Preferably, the ratio of the side length a of the rectangular column to the side length Px of the polymer supersurface structure unit is 11 / 50 to 7 / 25, the ratio of the distance d between two adjacent rectangular columns to the side length Px of the polymer supersurface structure unit is 11 / 50 to 7 / 25, and the ratio of the radius of the base of the cylinder to the side length Px of the polymer supersurface structure unit is 2 / 25 to 3 / 25.

[0013] Preferably, the rectangular columns and circular columns constituting the polymer metasurface structural unit are made of dielectric materials with a refractive index n>2.

[0014] The present invention also proposes a method for manufacturing a polymer dual-band refractive index sensor based on a continuous domain bound state, comprising:

[0015] Using SiH4 gas as Si source, a polycrystalline silicon film with a thickness of 300nm was grown on a silicon dioxide substrate by low pressure chemical vapor deposition;

[0016] A layer of photoresist is spin-coated on the polysilicon film using a coating machine, and after heating and curing, it is exposed to electron beam lithography to produce a photoresist array of a polymer super surface on the polysilicon film;

[0017] The Si film was vertically etched using selective dry etching with SF6 and C4F8 gases to form a polymer metasurface structural unit, and the photoresist residues were removed by dry oxygen etching to complete the fabrication of the polymer dual-band refractive index sensor.

[0018] Compared with the prior art, the present invention has the following significant advantages:

[0019] 1. Compared with the conventional method of achieving quasi-BIC by controlling slight geometric perturbations or displacement parameters to break the structural symmetry, the polymer metasurface has lower requirements on perturbation and displacement parameters and no specific requirements on structural shape. It has a simple structure and is robust, which is very conducive to processing and manufacturing.

[0020] 2. The introduction of a cylinder in the center of the structure not only breaks the symmetry of the structure and thus realizes a practical quasi-BIC, but also acts as a coupler to further enhance the near-field enhancement effect in the central area, making the metasurface interact more closely with the object to be measured, which is more conducive to obtaining better sensing performance in actual measurements.

[0021] 3. The polymer metasurface sensor can simultaneously excite dual quasi-BICs dominated by circular dipoles and magnetic dipole-electric quadrupoles, both of which can produce huge near-field enhancement, and realize extremely narrow Fano-type resonance spectra and higher Q values ​​in the transmission spectra. The characteristics of dual bands and narrow line width are more conducive to improving the detection accuracy and resolution of the sensor in actual detection.

[0022] 4. The polymer metasurface structure has geometric symmetry and is polarization-insensitive to incident light. In practical applications, it is not affected by the polarization state of incident light and has a wider range of applications.

[0023] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0025] Figure 1 It is a schematic diagram of the structure of the polymer dual-band refractive index sensor based on the continuous domain bound state in the present invention.

[0026] Figure 2 This is a top view of the xy plane of the polymer supersurface unit of the present invention. The cross-dashed lines in the figure are only used as a reference for equal division of the area and have no practical significance.

[0027] Figure 3 The figure is a schematic flow chart of the production method of the present invention.

[0028] Figure 4 Schematic diagram of the resonant wavelength shift when measuring liquids with different refractive indices with normal incidence of X-polarized light (polarization direction is parallel to the x-axis).

[0029] Figure 5 This is a schematic diagram of sensor sensitivity fitting, and the slope of the straight line is the sensor sensitivity.

[0030] Figure symbols: silicon dioxide substrate-1; square cylinder-2; central cylinder-3; height of rectangular cylinder and cylinder-h; thickness of silicon dioxide substrate-t; side length of the bottom surface of the rectangular cylinder-a; radius of the bottom surface of the cylinder-r; distance between adjacent rectangular cylinders-d. DETAILED DESCRIPTION

[0031] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can imagine various embodiments of the present invention. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or limitation of the technical solution of the present invention. On the contrary, the purpose of providing these embodiments is to enable those skilled in the art to understand the present invention more thoroughly. The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the innovative concept of the present invention.

[0032] It should be noted that if the embodiments of the present invention involve directional indications such as up, down, left, right, front, back, etc., then the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture as shown in the accompanying drawings. If the specific posture changes, the directional indication will also change accordingly.

[0033] In the first embodiment, if Figure 1 As shown, a polymer dual-band refractive index sensor based on continuous domain bound state, the polymer refractive index sensor includes a silicon dioxide substrate and a polymer metasurface unit periodically distributed on the silicon dioxide substrate, the material of the polymer metasurface is polycrystalline silicon, combined with Figure 2 The polymer supersurface structural unit is composed of four rectangular columns of exactly the same size and one circular column. The four rectangular columns have the same base and height and are located at the center of one quarter of the structural unit, and the circular column is located at the center of the structural unit.

[0034] The polymer metasurface sensor is centrally symmetrical about the x and y directions, and consists of two layers in the z direction, the bottom layer is a 300nm thick silicon dioxide substrate, and the upper layer is a polymer metasurface. The height of the rectangular columns and cylinders constituting the polymer is 300nm, the side length of the bottom surface of the rectangular column is 200nm, the radius of the bottom surface of the cylinder is 84nm, and the metasurface array period is 800nm.

[0035] Furthermore, without changing the structure of the polymer metasurface sensor, the proportional scaling structure can achieve a linear change in the resonance wavelength.

[0036] The four rectangular columns of the metasurface unit will excite circular dipole resonance in the xy plane, and the four rectangular columns of the two adjacent units will also excite circular dipole resonance. The superimposed field enhancement effect of the two will jointly produce a short-wavelength resonance mode (mode 1). The central cylinder acts as a coupler to greatly enhance the electric field in the central area of ​​the structure. The four rectangular columns and the central cylinder of the metasurface unit will form a magnetic dipole resonance in the xz plane, and the electric fields they form will superimpose on each other to produce a long-wavelength resonance mode (mode 2).

[0037] The structure of the polymer metasurface sensor is geometrically symmetrical and is polarization-insensitive to incident light, and is not affected by the polarization state of incident light in practical applications.

[0038] In a second embodiment, the combination Figure 3 , provides a method for making a polymer dual-band refractive index sensor based on a continuous domain bound state, the detailed method is as follows:

[0039] A method for manufacturing a polymer dual-band refractive index sensor based on a continuous domain bound state, comprising:

[0040] Step 1: Using SiH4 gas as a Si source, a polycrystalline silicon film with a thickness of 300 nm is grown on a silicon dioxide substrate by low-pressure chemical vapor deposition.

[0041] Step 2: Use a coating machine to spin-coat a layer of photoresist on the polysilicon film, heat and cure it, and then expose it to electron beam lithography to make a photoresist array of the polymer super surface on the polysilicon film.

[0042] Step 3: Use SF6 and C4F8 gases to vertically etch the Si film using selective dry etching to form a polymer metasurface array distributed on the silicon dioxide substrate.

[0043] Step 4: Use dry oxygen etching to remove the photoresist residues to form a polymer dual-band refractive index sensor based on continuous domain bound states.

[0044] In the simulation, periodic boundary conditions are used in the x and y directions, and PML boundary conditions are used in the z direction. A monitor is set at 600nm on the substrate. The type is 2D Z-normal, the monitoring band is 1200nm~1500nm, and the frequency point is 600. A light source is set 400nm above the structure. The incident light source is a plane wave. The incident area contains a single nanoring structural unit. During the simulation, an FDTD three-dimensional scan is performed on the above single nanoring. The simulation mesh area contains the above single nanoring, and the mesh accuracy is set to dx=dy=dz=4nm. Figure 4 As shown in the figure, when the background refractive index is linearly increased with a step length of 0.01 based on 1.43, the resonance peak of the transmission spectrum of the polymer metasurface dual-band refractive index sensor proposed in the present invention also redshifts. The calculation formula of the sensitivity of the known sensor is S = Δλ / Δn, where Δλ is the change in the resonance wavelength and Δn is the change in the refractive index. Figure 5 As shown in the figure, the sensitivity of the two resonant sensing bands of the sensor of the present invention can be fitted by simulation data, and the sensitivity is S1 = 527nm / RIU, S2 = 427nm / RIU respectively. The polymer dual-band refractive index sensor based on the continuous domain bound state of the present invention has a great near-field enhancement effect. Accordingly, the Q value of the dual resonance peak can reach 10 6 (Mode 1) and 10 7 (Mode 2) Order of magnitude.

[0045] When the relative position of the metasurface structure array remains unchanged, a dual-quasi-BIC transmission spectrum with a high Q value can still be obtained by changing the array geometry within an appropriate range, which fully demonstrates the robustness of the polymer dual-band refractive index sensor based on continuous and bound states.

[0046] The purpose of the present invention is to provide a polymer dual-band refractive index sensor based on continuous domain bound state and its manufacturing method, which has the characteristics of dual channels, high sensitivity, high Q value, robustness, customizability, polarization insensitivity, etc. At the same time, the structure is simple and easy to manufacture and process, and has a relatively broad application prospect in the fields of actual biochemical detection, food processing, medical monitoring, etc.

[0047] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0048] It should be understood that in order to simplify the present invention and help those skilled in the art understand the various aspects of the present invention, in the above description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes described in a single embodiment or described with reference to a single figure. However, the present invention should not be interpreted as the features included in the exemplary embodiments are all necessary technical features of the patent claims.

[0049] It should be understood that the modules, units, components, etc. included in the device of an embodiment of the present invention can be adaptively changed to be set in a device different from the embodiment. The different modules, units, or components included in the device of the embodiment can be combined into one module, unit, or component, or they can be divided into multiple sub-modules, sub-units, or sub-components.

Claims

1. A polymer dual-band refractive index sensor based on continuous domain bound state, characterized in that: The invention comprises a silicon dioxide substrate (1) and a polymer super surface structure unit which is distributed in an array on the upper surface of the silicon dioxide substrate (1), wherein the polymer super surface structure unit comprises four regular even polygonal cylinders of exactly the same size and a cylinder (3), wherein the regular even polygonal cylinders and the cylinder (3) are perpendicular to the silicon dioxide substrate (1), the regular even polygonal cylinders are arranged in a matrix, and the cylinder (3) is located at the center of the four regular even polygonal cylinders.

2. The polymer dual-band refractive index sensor based on continuous domain bound state according to claim 1, characterized in that: The regular even polygonal column is a rectangular column (2).

3. The polymer dual-band refractive index sensor based on continuous domain bound state according to claim 2, characterized in that: The rectangular column (2) and the circular column (3) have the same height.

4. The polymer dual-band refractive index sensor based on continuous domain bound state according to claim 3, characterized in that: The heights of the rectangular columns (2) and the circular columns (3) are equal to the thickness of the silicon dioxide substrate (1).

5. The polymer dual-band refractive index sensor based on continuous domain bound state according to claim 2, characterized in that: The bottom surfaces of the four rectangular columns (2) are squares with a side length of a, and the centers of the four rectangular columns (2) are respectively located at one quarter of the polymer supersurface structural unit.

6. The polymer dual-band refractive index sensor based on continuous domain bound state according to claim 2, characterized in that: The ratio of the side length a of the rectangular column (2) to the side length Px of the polymer supersurface structure unit is 11 / 50 to 7 / 25, the ratio of the distance d between two adjacent rectangular columns (2) to the side length Px of the polymer supersurface structure unit is 11 / 50 to 7 / 25, and the ratio of the bottom radius of the cylinder (3) to the side length Px of the polymer supersurface structure unit is 2 / 25 to 3 / 25.

7. The polymer dual-band refractive index sensor based on continuous domain bound state according to claim 2, characterized in that: The materials of the rectangular columns (2) and the circular columns (3) constituting the polymer super surface structural units are dielectric materials with a refractive index n>2.

8. A method for manufacturing a polymer dual-band refractive index sensor based on continuous domain bound states as claimed in any one of claims 1 to 7, characterized in that: include: Polycrystalline silicon thin film grown on a silicon dioxide substrate by low pressure chemical vapor deposition using SiH4 gas as a Si source; A layer of photoresist is spin-coated on the polysilicon film using a coating machine, and after heating and curing, it is exposed to electron beam lithography to produce a photoresist array of a polymer super surface on the polysilicon film; The Si film was vertically etched using selective dry etching with SF6 and C4F8 gases to form a polymer metasurface structural unit, and the photoresist residues were removed by dry oxygen etching to complete the fabrication of the polymer dual-band refractive index sensor.

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