Grating metasurface refractive index sensor with adjustable electrogenerated BIC and method

Abstract

The invention discloses an electrogenerated BIC adjustable grating metasurface refractive index sensor and method. The sensor comprises a substrate connected with an electrode, and a light reflecting layer is arranged on the lower surface of the substrate; arranging a grating layer on the upper surface of the substrate; the grating layer comprises a plurality of gratings which are periodically arranged on the substrate; when voltage is applied to the electrodes, the substrate can generate electrostrictive strain, and the period between the gratings is changed. The purpose of BIC tuning can be achieved by changing the voltage applied to the electrodes.

Description

Technical Field

[0001] The present invention relates to the technical field of metasurface sensors, and in particular to an electrically induced BIC-adjustable grating metasurface refractive index sensor and method. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Micro / nano-optical sensors (MNOSs) provide more degrees of freedom for nanoscale optical manipulation due to their high integration, high sensitivity and low cost. Metasurface sensors, as an important component of micro / nano-optical sensors, are artificial periodic structures on a subwavelength scale, which provide more degrees of freedom, high-sensitivity detection and packaging feasibility for micro / nano-optical manipulation. Their continuous domain bound states (BICs) can effectively avoid radiation loss and realize the detection of weak signals, thus effectively realizing high-sensitivity refractive index sensing.

[0004] When faced with a variety of samples to be tested, sensor devices with fixed optical modes may not be suitable for detection in all bands and cannot be tuned according to the diversity of samples to be tested, which greatly reduces the universality of this type of device. Therefore, it is extremely difficult to control the optical mode within a wide frequency range without permanently changing the geometry or material of the device. So far, although methods based on temperature changes, free carrier injection, and gas condensation can achieve reversible frequency tuning, the small control range limits its application. Obviously, reversible tuning of optical micro-nano devices over a large range remains a major challenge. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes an electrically BIC-adjustable grating metasurface refractive index sensor and method, which can achieve the purpose of BIC tuning by changing the voltage applied to the electrode.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] First, an electro-BIC-adjustable grating metasurface refractive index sensor is proposed, comprising a substrate connected to an electrode, a light reflecting layer arranged on the lower surface of the substrate; a grating layer is arranged on the upper surface of the substrate; the grating layer comprises a plurality of gratings, and the plurality of gratings are periodically arranged on the substrate; when a voltage is applied to the electrode, the substrate can generate electro-strain to change the period between the gratings.

[0008] Furthermore, the substrate is made of dielectric elastic material.

[0009] Furthermore, the greater the voltage applied to the electrode, the greater the electrostrain of the substrate.

[0010] Furthermore, the voltage applied to the electrode can reduce the thickness of the substrate and increase the period between the gratings.

[0011] Furthermore, the substrate is a pre-stretched substrate, and the pre-stretching direction of the substrate is consistent with the periodic arrangement direction of the grating.

[0012] Furthermore, the pre-stretching rate of the substrate is greater than or equal to 290% and less than or equal to 330%.

[0013] Furthermore, the light reflecting layer is made of Ag material.

[0014] Furthermore, the grating is made of Au material.

[0015] In the second aspect, a method for preparing an electrically induced BIC-adjustable grating metasurface refractive index sensor is proposed, comprising:

[0016] preparing a substrate;

[0017] A plurality of gratings are periodically deposited on the upper surface of the substrate;

[0018] A light reflecting layer is coated on the lower surface of the substrate.

[0019] Further, the substrate is pre-stretched;

[0020] depositing a grating on the upper surface of the pre-stretched substrate;

[0021] A light reflecting layer is coated on the lower surface of the pre-stretched substrate.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention proposes an electro-induced BIC-adjustable grating metasurface refractive index sensor and method. The sensor comprises a substrate connected with electrodes, a grating on the upper surface of the substrate and a light reflecting layer on the lower surface of the substrate. By applying a voltage to the electrodes, the substrate generates electro-induced strain, so that the period between the gratings and the structural parameters of the substrate are changed, thereby achieving the purpose of BIC tuning, and thus being applied to refractive index sensing applications.

[0024] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0026] Figure 1 A schematic diagram of the structure of an electrically induced BIC-adjustable grating metasurface refractive index sensor disclosed in an embodiment;

[0027] Figure 2 An analysis process of an electrically induced BIC-adjustable grating metasurface refractive index sensor disclosed in an embodiment;

[0028] Figure 3 A stress distribution diagram of a substrate disclosed in an embodiment;

[0029] Figure 4 A diagram showing the relationship between substrate stress, central strain and thickness disclosed in the embodiment;

[0030] Figure 5 A schematic diagram of the electrostrain sensor disclosed in the embodiment;

[0031] Figure 6 A diagram showing the relationship between voltage and strain in the embodiment disclosed;

[0032] Figure 7 A reflection spectrum energy band diagram of the grating metasurface disclosed in the embodiment;

[0033] Figure 8 1 is a diagram of the modes excited at different incident angles disclosed in the embodiment, wherein (a) is a diagram of the FP mode excited at vertical incidence, and (b) is a diagram of the quasi-BIC mode formed by the interference between the metal-dielectric hybrid GMR mode and the FP mode at an incident angle of 8.9°.

[0034] (c) is a quasi-BIC mode diagram formed by the interference between the SPP mode and the FP mode at an incident angle of 17°;

[0035] Fig. 9 1 is a reflection spectrum diagram under different voltages disclosed in the embodiment, wherein (a) is a reflection spectrum diagram under a voltage of 8000V, (b) is a reflection spectrum diagram under a voltage of 8000V, and (c) is a reflection spectrum diagram under a voltage of 8000V;

[0036] Fig.10 The reflectance spectrum corresponding to the SPP-FP quasi-BIC mode when the voltage disclosed in the embodiment is 8000V;

[0037] Fig.11 Graph showing the relationship between the resonant wavelength and the refractive index of the SPP-FP quasi-BIC mode disclosed in the embodiment. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0041] In the present invention, the directions or positional relationships indicated by terms such as "upper" and "lower" are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention. They do not specifically refer to any part or element in the present invention and should not be understood as limitations on the present invention.

[0042] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0043] Example 1

[0044] In order to achieve large-scale frequency tuning of optical micro-nano devices, in this embodiment, an electrically induced BIC-adjustable grating metasurface refractive index sensor is disclosed, and a periodic metasurface device is designed on a flexible substrate in combination with the high light transmittance, strong chemical inertness, high thermal stability, isotropy and uniformity of flexible materials. The device can use a strong local field of light to achieve strong light-matter interaction, and by adjusting the voltage applied to the device substrate, the period size of the metasurface device and the thickness of the substrate are changed, ultimately achieving the purpose of tuning the BIC wavelength.

[0045] This embodiment discloses an electrically induced BIC-adjustable grating metasurface refractive index sensor, such as Figure 1 , Figure 2 As shown, it includes a substrate connected to an electrode, a light reflecting layer is arranged on the lower surface of the substrate; a grating layer is arranged on the upper surface of the substrate; the grating layer includes a plurality of gratings, and the plurality of gratings are periodically arranged on the substrate; when a voltage is applied to the electrode, the substrate can generate electro-induced strain to change the period between the gratings.

[0046] In this embodiment, a voltage is applied to the electrode to generate electro-induced strain on the substrate, so that the period of the metasurface structure and the substrate structure parameters change, thereby achieving the purpose of BIC tuning, and thus being applied to refractive index sensing applications.

[0047] In a specific implementation, the substrate is made of a dielectric elastic material, which may be PDMS (polydimethylsiloxane), and the electrode is a flexible electrode, which is arranged on the lower surface of the substrate.

[0048] The light reflection layer is made of Ag (silver) material; the grating is made of Au (gold) material.

[0049] This embodiment discloses an electrically BIC-adjustable grating metasurface refractive index sensor, wherein the substrate is a pre-stretched substrate, and the pre-stretching direction of the substrate is consistent with the periodic arrangement direction of the grating.

[0050] In this embodiment, a pre-stretching simulation experiment is performed on the dielectric elastic material, and the relationship between the pre-stretching and the strain is analyzed according to the simulation experiment. Based on the relationship between the pre-stretching and the strain, the pre-stretching rate of the substrate is determined.

[0051] Specifically, the physical field of the pre-stretching simulation experiment of the dielectric elastic material adopts solid mechanics and electrostatics, wherein PDMS is set as the dielectric elastic material, the material model adopted is Mooney-Rivlin dual parameter, and the model parameter C 10 and C 01 are 75.5MPa and 5.7MPa respectively, and the bulk modulus κ is 962MPa. Figure 3 The stress distribution diagram shown shows that the stress is mainly distributed around the material, so the middle part can be used as the substrate of the grating metasurface structure. The size of the dielectric elastic material model is set to 8mm×8mm×1mm. Figure 3 The relationship between the thickness of PDMS and the central stress distribution under different pre-stretching amounts. In order to ensure a good electro-induced response and to prevent electrical breakdown caused by an overly thin substrate, the pre-stretching rate of the substrate in the sensor disclosed in this embodiment is determined to be greater than or equal to 290%, less than or equal to 330%, and preferably 300%.

[0052] The substrate thickness T is greater than or equal to 400 μm and less than or equal to 1100 μm.

[0053] In this embodiment, a grating layer is deposited on a pre-stretched substrate. The grating layer includes a plurality of gratings. The plurality of gratings are arranged in an equal period on the substrate, and the periodic arrangement direction of the gratings is consistent with the strain direction in the length direction of the substrate.

[0054] The grating thickness t is greater than or equal to 30 μm and less than or equal to 40 μm, preferably 35 μm; the grating period P is greater than or equal to 450 μm and less than or equal to 650 μm, preferably 550 μm; the grating width D is greater than or equal to 225 μm and less than or equal to 325 μm, preferably 275 μm.

[0055] When the initial voltage is set to 8000 V, the resonant wavelength λ is determined by the grating thickness t = 35 μm, the duty cycle f = 0.55, the period P = 550 μm and the incident light direction θ, as shown in formula (1):

[0056]

[0057] Where n c is the refractive index of the environment to be measured, θ is the incident angle, m = 0, ± 1, ... is the diffraction order, n eff is the effective refractive index of the grating structure. Therefore, any specific resonant wavelength λ can be obtained by adjusting the setting period P of the grating. The effective refractive index n eff The refractive index n of the surrounding environment c , high refractive index layer and low refractive index layer, as shown in formula (2):

[0058]

[0059] Where E(x,y) and ε(x,y) are the electric field value and dielectric constant of the grating metasurface structure, respectively.

[0060] like Figure 5 As shown, the voltage applied to the electrode in this embodiment can reduce the thickness of the substrate and increase the period between the gratings; and the greater the voltage applied to the electrode, the greater the electro-induced strain of the substrate.

[0061] This embodiment takes the deposition of a grating on a pre-stretched PDMS substrate as an example, changes the voltage value on the electrode below the substrate, analyzes the strain of the PDMS substrate under different voltages, and determines the relationship between the substrate strain and the voltage.

[0062] Polydimethylsiloxane film (PDMS), as a dielectric elastomer (DE), has excellent biocompatibility, non-toxicity, low Young's modulus and other characteristics. It can avoid the problems of electromechanical coupling efficiency changing significantly over time and the high viscosity of polyacrylate film (VHB) in the past. Figure 5 Schematic diagram of electrostrain of grating metasurface. Figure 6 is the curve of the change of PDMS substrate strain with applied voltage. It can be seen that with the increase of voltage, the deformation of the PDMS substrate gradually increases, and changes linearly in the range of 8000V-10000V, and the slope of the fitting line is about 4μm / 100V; according to the curve of the change of substrate strain with applied voltage.

[0063] This embodiment also calculates the BIC of the grating under different strains, and analyzes and constructs a relationship equation between the BIC mode and the voltage based on the relationship between the substrate strain and the voltage.

[0064] To study the adjustability of the electro-induced BIC mode, the corresponding reflection spectrum is also set to 8000 V with an incident angle range of -60° to 60° and a wavelength range of 600nm to 1100nm. At this time, the PDMS layer thickness T = 500μm and the grating period P = 550μm. Figure 7 The △ in the middle represents the FP cavity mode, which is the FP mode excited under vertical incidence and has a low correlation with the incident angle; ◇ represents the GMR-FP quasi-BIC mode, which is a quasi-BIC mode caused by the interference between the metal-medium hybrid guided mode resonance mode (GMR mode) and the FP mode at an incident angle of 8.9°. The GMR mode is shown as the solid line and has a high correlation with the angle; □ represents the SPR-FP quasi-BIC mode, which is a quasi-BIC mode formed by the interference between the SPP mode and the FP mode at an incident angle of 17°. The SPP mode is shown as the dotted line and has a high correlation with the incident angle. Figure 8 (a), (b), and (c) correspond to the distribution of the electric field |E| in the xz plane of the FP mode, the hybrid GMR-FP quasi-BIC mode, and the SPP-FP quasi-BIC mode, respectively.

[0065] Taking the SPP-FP quasi-BIC mode as an example, the effect of PDMS substrate thickness on the BIC mode under different voltages was studied. As the voltage value increases, the PDMS deforms due to the electrostrain effect, so its thickness T decreases and the grating period P increases. Fig. 9 (a)-(c) It can be seen that the increase in voltage value leads to the red shift of the resonant wavelength of the FP mode, which is caused by the optical interference between the gold nanograting and the underlying silver light reflection layer. When the frequency of the FP resonant mode overlaps with the frequency of the surface plasmon mode in the gold nanograting, the line width of the FP mode decreases. In general, as the voltage value increases, the resonant wavelength of the SPP-FP quasi-BIC mode red shifts and the BIC excitation angle becomes smaller.

[0066] This embodiment also applies the obtained adjustable BIC metasurface device to refractive index sensing and analyzes its sensitivity changes in different tuning bands.

[0067] Taking the SPR-FP quasi-BIC mode as an example, refractive index sensing analysis was performed. Fig.10 The reflection spectrum corresponding to the SPR-FP quasi-BIC mode at a voltage of 8000 V. When the refractive index of the grating top medium changes from 1.00 to 1.33, the reflection spectrum has a narrow line width and shows a red shift. Fig.11 Figure 2 is the relationship between the resonant wavelength and the refractive index in the SPR-FP quasi-BIC mode. It can be seen that the resonant wavelength of the reflection spectrum changes linearly with the change of the refractive index, and the obtained refractive index sensitivity is 124nm / RIU.

[0068] The present embodiment discloses an electro-induced BIC-adjustable grating metasurface refractive index sensor, comprising a substrate connected to an electrode, a grating on the upper surface of the substrate, and a light reflecting layer on the lower surface of the substrate; by applying a voltage to the electrode, the substrate generates electro-induced strain, so that the period between the gratings and the structural parameters of the substrate change, thereby achieving the purpose of BIC tuning, and thus being applied to refractive index sensing applications

[0069] Example 2

[0070] In this embodiment, a method for preparing an electrically induced BIC-adjustable grating metasurface refractive index sensor is disclosed, comprising:

[0071] preparing a substrate;

[0072] A plurality of gratings are periodically deposited on the upper surface of the substrate;

[0073] A light reflecting layer is coated on the lower surface of the substrate.

[0074] Further, the substrate is pre-stretched;

[0075] depositing a grating on the upper surface of the pre-stretched substrate;

[0076] A light reflecting layer is coated on the lower surface of the pre-stretched substrate.

[0077] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. An electrically induced BIC-adjustable grating metasurface refractive index sensor, characterized in that: It includes a substrate connected to an electrode, a light reflection layer is arranged on the lower surface of the substrate; a grating layer is arranged on the upper surface of the substrate; the grating layer includes a plurality of gratings, and the plurality of gratings are periodically arranged on the substrate; when a voltage is applied to the electrode, the substrate can generate electro-induced strain to change the period between the gratings.

2. The electro-BIC tunable grating metasurface refractive index sensor according to claim 1, characterized in that: The substrate is made of dielectric elastic material.

3. The electro-BIC tunable grating metasurface refractive index sensor according to claim 1, characterized in that: The greater the voltage applied to the electrodes, the greater the electrostrain of the substrate.

4. The electro-BIC tunable grating metasurface refractive index sensor according to claim 1, characterized in that: The voltage applied to the electrode can reduce the thickness of the substrate and increase the period between the gratings.

5. The electro-BIC tunable grating metasurface refractive index sensor according to claim 1, characterized in that: The substrate is a pre-stretched substrate, and the pre-stretching direction of the substrate is consistent with the periodic arrangement direction of the grating.

6. The electro-BIC tunable grating metasurface refractive index sensor according to claim 1, characterized in that: The pre-stretching rate of the substrate is greater than or equal to 290% and less than or equal to 330%.

7. The electro-BIC tunable grating metasurface refractive index sensor according to claim 1, characterized in that: The light reflecting layer is made of Ag material.

8. The electro-BIC tunable grating metasurface refractive index sensor according to claim 1, characterized in that: The grating is made of Au material.

9. A method for preparing an electrically induced BIC-adjustable grating metasurface refractive index sensor, characterized in that: include: preparing a substrate; A plurality of gratings are periodically deposited on the upper surface of the substrate; A light reflecting layer is coated on the lower surface of the substrate.

10. The method for preparing the electro-BIC adjustable grating metasurface refractive index sensor according to claim 9, characterized in that: Pre-stretching the substrate; depositing a grating on the upper surface of the pre-stretched substrate; A light reflecting layer is coated on the lower surface of the pre-stretched substrate.

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