Metasurface, refractive index sensor and method for realizing robust quasi-continuous domain bound state
By introducing a height difference between the humidity-driven deformable material layer and the dielectric layer in the metasurface, out-of-plane symmetry is broken, achieving stability and robustness of quasi-continuous bound-state resonance over a wide spectral range. This solves the problem of insufficient robustness of traditional in-plane symmetry-broken structures and is suitable for refractive index sensors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-22
- Publication Date
- 2026-03-27
AI Technical Summary
The realization of traditional quasi-continuous domain bound states relies on in-plane symmetry-broken structures, which suffer from low robustness, high sensitivity to structural parameters, and limited design freedom.
By employing a periodically arranged square lattice supercell structure, combined with a humidity-driven deformable material layer and a dielectric layer, the height difference of the nanopillars is dynamically controlled by the ambient humidity to break out-of-plane symmetry and form a hybrid out-of-plane symmetry metasurface, thereby achieving the stability and robustness of the quasi-continuous domain bound state.
It maintains stability of resonant wavelength and quality factor over a wide spectral range, reduces sensitivity to manufacturing errors and environmental disturbances, is suitable for refractive index sensors, and features narrower linewidth and higher robustness.
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Figure CN121741908A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of micro-nano photonics, and more particularly relates to a metasurface, a refractive index sensor and a method for realizing a robust quasi-continuous domain bound state. BACKGROUND
[0002] Continuous domain bound state and its derivative quasi-bound state continuous state are important research directions of micro-nano photonics, have infinite quality factor Q value and zero line width characteristics, and can significantly enhance light-matter interaction.
[0003] Traditional quasi-continuous domain bound state is realized by relying on in-plane symmetry breaking structure, although high Q value resonance can be excited, but there are obvious deficiencies, including: high sensitivity of structure parameters, slight error will cause Q value to drop significantly and resonance wavelength to drift; limited design freedom, it is difficult to balance multi-parameter regulation and stability requirements. How to overcome the deficiencies of traditional structure design and develop a new type of optical metasurface structure with high robustness has become a key problem to be broken through in the field. SUMMARY
[0004] The application provides a metasurface, a refractive index sensor and a method for realizing a robust quasi-continuous domain bound state, which solves the problem of low robustness in the prior art that the realization of quasi-continuous domain bound state relies on in-plane symmetry breaking structure.
[0005] In a first aspect, the application provides a metasurface, which comprises a plurality of square lattice supercells arranged periodically; each square lattice supercell comprises a substrate layer, and a first nanorod and a second nanorod located on the substrate layer; the first nanorod is a double-layer composite structure comprising a humidity-driven deformable material layer as a bottom and a first dielectric layer as a top; the second nanorod is a single-layer structure comprising a second dielectric layer; the first dielectric layer and the second dielectric layer have the same height; the metasurface dynamically regulates the height difference between the first nanorod and the second nanorod based on environmental humidity.
[0006] Preferably, the first nanorod is located at the center of the lattice point of a square lattice formed by four second nanorods, and the second nanorod is located at the center of the lattice point of a square lattice formed by four first nanorods.
[0007] Preferably, the size of the first nanorod, the size of the second nanorod, and the interlayer spacing between the first nanorod and the second nanorod are all subwavelength scales.
[0008] Preferably, the humidity-driven deformable material layer is prepared by using a hydrogel, the first dielectric layer and the second dielectric layer are both prepared by using silicon, and the substrate layer is prepared by using silicon dioxide.
[0009] Preferably, the humidity-driven deformable material layer, the first dielectric layer and the second dielectric layer have the same planar shape and the same planar outer profile size.
[0010] Preferably, the humidity-driven deformable material layer, the first dielectric layer and the second dielectric layer are all cylinders and have the same diameter; or, the humidity-driven deformable material layer, the first dielectric layer and the second dielectric layer are all cuboids and have the same width and length.
[0011] Preferably, the quasi-continuous domain bound state resonance of the metasurface is not sensitive to the incident angle; when the asymmetry parameter changes, the quasi-continuous domain bound state resonance characteristics of the metasurface have high stability; the asymmetry parameter includes the height of the humidity-driven deformable material layer and the planar outer profile size; the quasi-continuous domain bound state resonance characteristics include resonance wavelength, quality factor and modulation depth at resonance wavelength.
[0012] Preferably, the metasurface can realize quasi-continuous domain bound state regulation in a wide spectral range from ultraviolet to near infrared.
[0013] In a second aspect, the present application provides a refractive index sensor comprising the metasurface provided in the first aspect of the present application.
[0014] In a third aspect, the present application provides a method for realizing robust quasi-continuous domain bound state, which realizes robust quasi-continuous domain bound state based on the metasurface provided in the first aspect of the present application.
[0015] One or more technical solutions provided in the present application have at least the following technical effects or advantages: The super surface provided by the application comprises a plurality of square lattice supercells arranged periodically; each square lattice supercell comprises a substrate layer, and a first nanorod and a second nanorod located on the substrate layer; the first nanorod is a double-layer composite structure (comprising a humidity-driven deformation material layer as a bottom and a first medium layer as a top), and the second nanorod is a single-layer structure (only comprising a second medium layer); the height of the first medium layer and the second medium layer is the same; the super surface dynamically regulates the height difference between the first nanorod and the second nanorod based on the environmental humidity. That is, the application provides a mixed out-of-plane symmetry breaking super surface, by arranging two nanorod structures with different heights in one supercell, vertical asymmetry is formed, by introducing local material difference, the modulation of optical properties in the out-of-plane direction is realized, and the material realizing the height difference in the application is a humidity-driven deformation material, so the height difference can be dynamically regulated by the environmental humidity, the super surface provided by the application shows a significantly narrower linewidth and a more stable resonance compared with the traditional design, and in a wide range of incident angles, the quasi-continuous domain bound state can still maintain a stable Q factor, resonance wavelength and modulation depth, and has good robustness. On this basis, a refractive index sensor can be constructed, and a robust quasi-continuous domain bound state can be realized based on the super surface. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1 FIG. 1 is a schematic diagram of the application based on a super surface to realize a robust quasi-continuous domain bound state.
[0017] Figure 2 FIG. 2 is a comparison diagram of a traditional super surface and the super surface provided by the application; wherein, Figure 2 (a) in FIG. 2 is a structural schematic diagram of a traditional in-plane symmetry breaking super surface, Figure 2 (b) in FIG. 2 is a structural schematic diagram of a mixed out-of-plane symmetry breaking super surface provided by the application.
[0018] Figure 3 FIG. 3 is a comparison diagram of the transmission spectrum of the quasi-continuous domain bound state of the traditional in-plane symmetry breaking super surface and the mixed out-of-plane symmetry breaking super surface provided by the application under different asymmetric parameters.
[0019] Figure 4 FIG. 4 is a simulated transmission spectrum contour diagram of the super surface; wherein, Figure 4 (a) in FIG. 4 is a simulated transmission spectrum contour diagram of the traditional in-plane symmetry breaking super surface, Figure 4 (b) in FIG. 4 is a simulated transmission spectrum contour diagram of the mixed out-of-plane symmetry breaking super surface provided by the application.
[0020] Figure 5 FIG. 5 is a diagram of the relationship between the quality factor Q and the resonance wavelength of the quasi-continuous domain bound state of the super surface and the breaking parameter; wherein, Figure 5(b) of figure 1 is a relationship diagram of the quality factor Q and the resonant wavelength of the quasi-continuous domain bound state of the mixed out-of-plane symmetry broken super surface provided by the present application versus the broken parameter. Figure 5 (b) of figure 1 is a relationship diagram of the quality factor Q and the resonant wavelength of the quasi-continuous domain bound state of the mixed out-of-plane symmetry broken super surface provided by the present application versus the broken parameter.
[0021] Figure 6 is the quasi-continuous domain bound state transmission spectrum and the fitting result of the Fano model when δh=80nm of the present application.
[0022] Figure 7 is the x-y and x-z plane electric field distribution diagram of the super surface at the quasi-continuous domain bound state resonant wavelength; wherein, Figure 7 (a) of figure 1 is the x-y plane electric field distribution diagram of the traditional in-plane symmetry broken super surface, Figure 7 (b) of figure 1 is the x-z plane electric field distribution diagram of the mixed out-of-plane symmetry broken super surface provided by the present application.
[0023] Figure 8 is the simulation transmission spectrum diagram of the mixed out-of-plane symmetry broken super surface provided by the present application when the incident angle changes from 0° to 6°.
[0024] Figure 9 is the relationship diagram of the quality factor, the resonant wavelength and the modulation depth of the mixed out-of-plane symmetry broken super surface provided by the present application versus the incident angle.
[0025] Figure 10 is the electric field distribution diagram of the quasi-continuous domain bound state resonance caused by the symmetry broken parameter δh of the mixed out-of-plane symmetry broken super surface provided by the present application when the incident angle is 0° and 6°.
[0026] Figure 11 is the structure diagram of the rectangular dimer super surface; wherein, Figure 11 (a) of figure 1 is the structure diagram of the traditional in-plane symmetry broken super surface, Figure 11 (b) of figure 1 is the structure diagram of the mixed out-of-plane symmetry broken super surface provided by the present application.
[0027] Figure 12 is Figure 11 the simulation transmission spectrum contour diagram of the rectangular dimer super surface provided by the present application; wherein, Figure 12 (a) of figure 1 is the simulation transmission spectrum contour diagram of the traditional in-plane symmetry broken super surface, Figure 12 (b) of figure 1 is the simulation transmission spectrum contour diagram of the mixed out-of-plane symmetry broken super surface provided by the present application.
[0028] Figure 13 is Figure 11The provided rectangular dimer metasurface corresponds to the quasi-continuous and bound state quality factor Q and resonance wavelength change with the broken parameter relationship diagram; wherein, Figure 13 In (a), the quasi-continuous and bound state quality factor Q and resonance wavelength change with the broken parameter relationship diagram of the traditional in-plane symmetry broken metasurface, Figure 13 In (b), the quasi-continuous and bound state quality factor Q and resonance wavelength change with the broken parameter relationship diagram of the mixed out-of-plane symmetry broken metasurface provided by the application.
[0029] Figure 14 It is the simulation transmission spectrum contour map of the metasurface corresponding to the change of refractive index; wherein, Figure 14 In (a), the simulation transmission spectrum contour map of the mixed out-of-plane symmetry broken metasurface provided by the application, Figure 14 In (b), the simulation transmission spectrum contour map of the traditional in-plane symmetry broken metasurface.
[0030] Figure 15 It is the corresponding line graph of the transmission spectrum of the metasurface under different refractive indexes n; wherein, Figure 15 In (a), the corresponding line graph of the transmission spectrum of the traditional in-plane symmetry broken metasurface, Figure 15 In (b), the corresponding line graph of the transmission spectrum of the mixed out-of-plane symmetry broken metasurface provided by the application.
[0031] Figure 16 It is the function relationship graph of the quasi-continuous domain bound state resonance wavelength of the metasurface corresponding to the change of refractive index; wherein, Figure 16 In (a), the function relationship graph of the quasi-continuous domain bound state resonance wavelength of the mixed out-of-plane symmetry broken metasurface provided by the application, Figure 16 In (b), the function relationship graph of the quasi-continuous domain bound state resonance wavelength of the traditional in-plane symmetry broken metasurface corresponding to the change of refractive index.
[0032] Figure 17 It is the quality factor FOM graph of the metasurface under different refractive indexes; wherein, Figure 17 In (a), the quality factor FOM graph of the traditional in-plane symmetry broken metasurface, Figure 17 In (b), the quality factor FOM graph of the mixed out-of-plane symmetry broken metasurface provided by the application. DETAILED DESCRIPTION
[0033] In order to better understand the above technical solutions, the above technical solutions will be described in detail in combination with the drawings in the specification and specific embodiments.
[0034] Embodiment 1: Embodiment 1 provides a metasurface, comprising a plurality of square-lattice supercells arranged periodically; each of the square-lattice supercells comprises a substrate layer, and a first nanorod and a second nanorod located on the substrate layer; the first nanorod is a double-layer composite structure comprising a humidity-driven deformable material layer as a bottom and a first dielectric layer as a top; the second nanorod is a single-layer structure comprising a second dielectric layer; the first dielectric layer and the second dielectric layer have the same height; the metasurface dynamically regulates the height difference between the first nanorod and the second nanorod based on ambient humidity.
[0035] The first nanorod is located at the center of a square lattice formed by four second nanorods, and the second nanorod is located at the center of a square lattice formed by four first nanorods.
[0036] The size of the first nanorod, the size of the second nanorod, and the interlayer spacing between the first nanorod and the second nanorod are all subwavelength scales. That is, the square-lattice supercell in the present application is subwavelength in size, typically 50-300 nm.
[0037] For example, the humidity-driven deformable material layer can be prepared using a hydrogel, the first dielectric layer and the second dielectric layer can both be prepared using silicon, and the substrate layer can be prepared using silicon dioxide.
[0038] The humidity-driven deformable material layer, the first dielectric layer, and the second dielectric layer have the same planar shape and the same planar external profile size. For example, the humidity-driven deformable material layer, the first dielectric layer, and the second dielectric layer are all cylindrical and have the same diameter; or the humidity-driven deformable material layer, the first dielectric layer, and the second dielectric layer are all cuboids and have the same width and length.
[0039] The quasi-continuous domain bound state resonance of the metasurface is not sensitive to the incident angle; when the asymmetry parameter changes, the quasi-continuous domain bound state resonance characteristics of the metasurface have high stability; the asymmetry parameter includes the height of the humidity-driven deformable material layer and the planar external profile size; the quasi-continuous domain bound state resonance characteristics include resonance wavelength, quality factor, and modulation depth at resonance wavelength.
[0040] The metasurface can achieve quasi-continuous domain bound state regulation in a wide spectral range from ultraviolet to near-infrared.
[0041] The following parameters are used to further illustrate the present application.
[0042] The super surface provided by the present application is essentially a hybrid all-dielectric super surface, which can break the out-of-plane symmetry and realize robust quasi-continuous domain bound states, see Figure 1 . In order to verify the effect of the present application, two kinds of super surface structures are provided below, one is the super surface provided by the present application (i.e. hybrid out-of-plane symmetry breaking super surface), and the other is the traditional in-plane symmetry breaking super surface. Specifically, the structural schematic diagram of the traditional in-plane symmetry breaking super surface is shown in (a) of Figure 2 , and the structural schematic diagram of the hybrid out-of-plane symmetry breaking super surface provided by the present application is shown in (b) of Figure 2 , both of which adopt square lattice supercell arrangement with a period of p=800nm, and each supercell contains two nanocolumns (labeled as ND-1 and ND-2 respectively) deposited on a silicon dioxide substrate layer (thickness t=100nm). In the array, each ND-2 (or ND-1) is located at the four-fold symmetric site around ND-1 (or ND-2). That is, each ND-1 is located at the center position of the lattice point of the square lattice formed by four ND-2, and each ND-2 is located at the center position of the lattice point of the square lattice formed by four ND-1.
[0043] Taking the nanocolumn as a cylindrical structure as an example, for the traditional in-plane symmetry breaking super surface: the thickness of ND-1 and ND-2 is the same (h1=h2=100nm), the diameter of ND-1 is fixed as d1=150nm, and the x-y plane symmetry is broken by adjusting the diameter d2 of ND-2 to excite quasi-continuous domain bound states. For the hybrid out-of-plane symmetry breaking super surface provided by the present application: ND-2 is a pure silicon structure (thickness h2=100nm), and ND-1 adopts a double-layer composite structure of hydrogel+silicon (the thickness of the bottom hydrogel layer determines the height difference, and the thickness of the top silicon disc is h1=100nm), and the diameters of the two nanocolumns are the same (d1=d2=150nm).
[0044] In the simulation, the refractive index of silicon and silicon dioxide adopts the Palik database data, and the refractive index of hydrogel is set to 1.5. Through the electromagnetic simulation software FDTD Solutions, we calculated the relationship between the quasi-continuous domain bound state transmission spectrum and the asymmetric parameter of the two structures. It is found that, as shown by the dashed line in Figure 3 , the resonant wavelength of the traditional in-plane symmetry breaking super surface changes significantly with the asymmetric parameter, as shown by the solid line in Figure 3 , the quasi-continuous domain bound state resonant wavelength and the quality factor Q of the hybrid out-of-plane symmetry breaking super surface provided by the present application remain highly stable.
[0045] When the symmetry breaking parameters of the two structures change, the simulated transmission spectrum contour map is shown in Figure 4 . According to Figure 4As can be seen in (a) of the traditional in-plane symmetry-broken metasurface: d² / 2 changes from 150 nm to 60 nm, while the thicknesses of h1 and h2 remain constant at 100 nm. From Figure 4 As shown in (b), the out-of-plane symmetry-broken metasurface provided by this invention exhibits the following characteristics: when δh varies from 0 nm to 100 nm, the diameters of d1 and d2 remain constant at 150 nm. When d2 / 2 = d1 / 2 = 150 nm or δh = 0, i.e., when the symmetry is not broken, the resonance disappears. Furthermore, these two quasi-continuous domain bound state resonance modulation methods exhibit significantly different characteristics: in traditional in-plane symmetry-broken metasurfaces, the quasi-continuous domain bound state resonance shows a significant blue shift, accompanied by rapid linewidth broadening. However, in the out-of-plane symmetry-broken metasurface provided by this invention, increasing δh has almost no effect on the resonance wavelength or linewidth. Even at larger δh values, the quasi-continuous domain bound state mode still maintains a sharp peak and a stable wavelength, indicating very low radiation loss. This demonstrates that the metasurface structure provided by this invention is significantly superior to traditional in-plane symmetry-broken structures in terms of resonance modulation.
[0046] The relationship between the quality factor Q (left arrow curve) and resonant wavelength (right arrow curve) of the quasi-continuous bound state and the in-plane asymmetric parameters is as follows: Figure 5 As shown. Among them, Figure 5 (a) in the figure shows the relationship between the quality factor Q and the resonant wavelength of the bound state in the quasi-continuous domain of a traditional in-plane symmetry-broken metasurface and the breaking parameters. Figure 5 (b) in the figure shows the relationship between the quality factor Q and the resonant wavelength of the bound state in the quasi-continuous domain of the hybrid out-of-plane symmetry broken metasurface provided by the present invention and the breaking parameters. Figure 5 It can be seen that, with the change of the asymmetry parameter (d² / 2 or δh), in the traditional in-plane symmetry-broken metasurface, as d² / 2 decreases from 140 nm to 65 nm, the corresponding quasi-continuous domain bound state resonance wavelength blue-shifts from 980 nm to 940 nm. However, for the hybrid out-of-plane symmetry-broken metasurface provided by this invention, when δh increases from 20 nm to 100 nm, the quasi-continuous domain bound state resonance remains almost constant at approximately 985 nm. Compared to the former, the Q-factor of the hybrid out-of-plane symmetry-broken metasurface provided by this invention decays more slowly with the increase of the asymmetry parameter, exhibiting stronger robustness. That is, Figure 5 The results shown verify the high stability of the quasi-continuous domain bound state resonant wavelength and quality factor Q of the hybrid out-of-plane symmetry broken metasurface provided by this invention.
[0047] The resonance curve at δh=80nm was fitted using the typical Fano formula. Figure 6 ),from Figure 6As shown in the Fano analog transmission curve, the analog calculation curve is highly consistent with the fitting curve, further confirming the accuracy of the calculation Q factor.
[0048] Figure 7 are x-y and x-z plane electric field distribution diagrams of the super surface at the quasi-continuous domain bound state resonance wavelength, wherein, Figure 7 (a) in (a) is an x-y plane electric field distribution diagram of a traditional in-plane symmetry breaking super surface at the quasi-continuous domain bound state resonance wavelength, Figure 7 (b) in (b) is an x-z plane electric field distribution diagram of the mixed out-of-plane symmetry breaking super surface provided by the application at the quasi-continuous domain bound state resonance wavelength. Figure 7 It can be seen from the difference in electric field intensity of the two super surface structures (558 for the traditional in-plane symmetry breaking super surface and 2160 for the mixed out-of-plane symmetry breaking super surface provided by the application) that the mixed out-of-plane symmetry breaking super surface provided by the application significantly exceeds the effect that can be achieved by the traditional in-plane symmetry breaking super surface. Therefore, the highly driven geometric structure provided by the application becomes an ideal choice for enhancing the interface driving process, and has wide application prospects in the fields of biological spectroscopy and catalysis.
[0049] When the input structural parameters of the mixed out-of-plane symmetry breaking super surface provided by the application are d1=d2=150nm, δh=64nm, h1=h2=100nm, the analog transmission spectrum when the incident angle changes from 0° to 6° is as shown in Figure 8 According to Figure 8 It can be seen that when the vertical incidence changes to oblique incidence (corresponding to the incident angle changing from 0° to 6° in Figure 8 The quasi-continuous domain bound state resonance of the mixed out-of-plane symmetry breaking super surface provided by the application remains stable (shown as a narrow bandwidth, a modulation depth and a stable resonance wavelength in Figure 8
[0050] The relationship between the quality factor Q, the resonance wavelength and the modulation depth (MD) corresponding to the mixed out-of-plane symmetry breaking super surface provided by the application and the change of the incident angle is as shown in Figure 9 Figure 9 is the quality factor Q, the resonance wavelength and the modulation depth extracted from the transmission spectrum in Figure 8 According to Figure 9 It can be seen that the quality factor Q only decreases slightly with the increase of the incident angle, the resonance wavelength is shifted by no more than about 5 nm for the maximum oblique incident angle of 6°, and in addition, the modulation depth value at the resonance wavelength remains basically unchanged. This further illustrates that the quasi-continuous domain bound state resonance of the mixed out-of-plane symmetry breaking super surface provided by the application remains stable within a wide range of incident angles.
[0051] correspondingFigure 8 At incident angles of 0° and 6°, the electric field distribution of the quasi-continuous bound-state resonance caused by δh is as follows: Figure 10 As shown, according to Figure 10 It can be seen that at the resonant wavelength, the high field strength is still confined to the sides of the silicon nanopillars at 0° perpendicular incidence and 6° oblique incidence, and the intensity is higher than that at perpendicular incidence. This demonstrates that, through hybrid out-of-plane symmetry breaking, the quasi-continuous domain bound-state resonance is angle-independent, enabling the metasurface energy provided by this invention to be widely used in optical devices without requiring strict perpendicular incidence.
[0052] based on Figure 8 to Figure 10 It can be seen that, in addition to high stability, the hybrid out-of-plane symmetry broken metasurface provided by the present invention can also realize quasi-continuous domain bound states that are insensitive to the incident angle.
[0053] To verify the universality of the hybrid out-of-plane symmetry breaking mechanism provided by this invention, this invention further constructs as follows: Figure 11 The diagram shows the structure of the rectangular dimer metasurface; in which, Figure 11 (a) is a schematic diagram of a traditional in-plane symmetry-broken metasurface. Figure 11 Image (b) is a schematic diagram of the hybrid out-of-plane symmetry-breaking metasurface provided by this invention. In this example, the lattice period p = 1000 nm, the thickness of the silicon dielectric layer is h1 = h2 = 225 nm, the thickness of the silicon dioxide substrate layer is t = 200 nm, the length of the nanopillars is L = 480 nm, the width is W1 = (Ld) / 2, and the gap between the two nanopillars is d = 258 nm. Traditional in-plane manipulation achieves symmetry breaking through width offset δ, while the hybrid out-of-plane manipulation provided by this invention achieves breaking through the thickness δh of the hydrogel layer.
[0054] Figure 12 The transmission spectra of two types of structures were shown, among which, Figure 12 (a) is a simulated transmission spectrum contour plot of a traditional in-plane symmetry-broken metasurface. Figure 12 Image (b) shows the simulated transmission spectrum contour plot of the hybrid out-of-plane symmetry broken metasurface provided by this invention. Mode switching from continuous-domain bound states to quasi-continuous-domain bound states can be achieved by adjusting δ (width difference) or δh (height difference). Figure 12 As can be seen, compared with traditional in-plane broken metasurfaces, the quasi-continuous domain bound state resonance peak of the hybrid out-of-plane symmetry broken metasurface provided by the present invention exhibits a steeper slope as the asymmetry factor increases, indicating that its resonant wavelength is stable.
[0055] To quantify the effect of asymmetric parameters on resonance characteristics, Figure 13 The relationship between the quality factor Q and the resonant wavelength as a function of the breaking parameters was calculated. Figure 13(a) in the figure shows the relationship between the quality factor Q and the resonant wavelength of the quasi-continuous and bound states of a traditional in-plane symmetry-broken metasurface and the broken parameters. Figure 13 Figure (b) shows the relationship between the quality factor Q and resonant wavelength of the quasi-continuous and bound states of the hybrid out-of-plane symmetry-broken metasurface provided by this invention and the breaking parameters. The resonant wavelength of the bound state in the quasi-continuous domain of a traditional in-plane metasurface drifts by approximately 50 nm, while the resonant wavelength of the bound state in the quasi-continuous domain of the hybrid out-of-plane symmetry-broken metasurface of this invention remains stably maintained around 1295 nm. This result demonstrates that the hybrid out-of-plane structure provided by this invention can achieve quasi-continuous bound state resonance with wavelength stability.
[0056] To evaluate the RI (Refractive Index) sensing performance of the hybrid out-of-plane symmetry breaking mechanism, we also compared the optical properties of the metasurface provided by this invention with those of a traditional in-plane symmetry breaking metasurface. Figure 14 This is a simulated transmission spectrum contour plot of the metasurface corresponding to changes in refractive index; among which... Figure 14 (b) is a simulated transmission spectrum contour plot of a traditional in-plane symmetry-broken metasurface. Figure 14 Figure (a) shows the simulated transmission spectrum contour plot of the hybrid out-of-plane symmetry broken metasurface provided by this invention. The results show that the quasi-continuous and bound-state resonance peaks of both are highly sensitive to changes in refractive index. When the refractive index increases from 1.00 to 1.35, both the quasi-continuous and bound-state resonance wavelengths exhibit a gradual redshift, regardless of whether it is the traditional in-plane symmetry broken metasurface or the hybrid out-of-plane symmetry broken metasurface provided by this invention. However, compared to the traditional in-plane symmetry broken metasurface, the metasurface provided by this invention exhibits a significantly narrower resonance linewidth, achieving higher sensing accuracy, and is therefore more suitable for application in refractive index sensors.
[0057] Figure 15 This is a line graph showing the transmission spectra of the metasurface at different refractive indices n; where, Figure 15 (a) in the figure is the corresponding line diagram of the transmission spectrum of a traditional in-plane symmetry-broken metasurface. Figure 15 (b) is the corresponding line diagram of the transmission spectrum of the hybrid out-of-plane symmetry broken metasurface provided by the present invention. Figure 15 From left to right, the refractive index n increases. The results show that the quasi-continuous domain bound state resonance peak is highly sensitive to changes in environmental RI: when RI increases from 1.00 to 1.35, both types of structures exhibit a redshift of the resonance wavelength. However, the hybrid out-of-plane symmetry-broken metasurface provided by this invention exhibits a narrower resonance linewidth, which confirms the superiority of the metasurface of this invention in RI sensing applications.
[0058] Figure 16 This is a graph showing the functional relationship between the resonant wavelength of the quasi-continuous bound state corresponding to the metasurface and the refractive index; where,Figure 16 (a) in the figure is a function graph showing the relationship between the resonant wavelength of the quasi-continuous domain bound state and the refractive index of the hybrid out-of-plane symmetry broken metasurface provided by the present invention. Figure 16 Figure (b) shows the functional relationship between the resonant wavelength of the quasi-continuous bound state of a traditional in-plane symmetry-broken metasurface and the refractive index. By defining the sensitivity S = Δλ / Δn (Δλ is the wavelength shift and Δn is the refractive index change), the bulk sensitivity of the hybrid out-of-plane symmetry-broken metasurface provided by this invention is measured to be 455 nm / RIU, which is better than the 440 nm / RIU of the traditional in-plane structure.
[0059] Figure 17 These are the FOM (Form of Metrics) plots of metasurfaces with different refractive indices; among them, Figure 17 (a) is the FOM (Form of Metrics) plot of the quality factor for a traditional in-plane symmetry-broken metasurface. Figure 17 (b) is the quality factor FOM diagram of the hybrid out-of-plane symmetry broken metasurface provided by the present invention. The quality factor FOM analysis combining sensitivity, resolution and response speed shows that the FOM value of the hybrid out-of-plane symmetry broken metasurface provided by the present invention significantly exceeds that of traditional in-plane structures.
[0060] Example 2: Example 2 provides a refractive index sensor, including the metasurface as described in Example 1.
[0061] As can be seen from the description of Example 1, the metasurface provided by the present invention can be applied to a refractive index sensor, and therefore the metasurface provided in Example 1 can be used as the core component of a refractive index sensor.
[0062] The refractive index sensor may also include other conventional components, such as a light source, a detection device, and a signal acquisition and processing circuit, which can be configured according to application requirements.
[0063] Example 3: Example 3 provides a method for realizing robust quasi-continuous bound states, based on the metasurface described in Example 1.
[0064] That is, Example 3 provides a method for achieving robust quasi-continuous bound states in a metasurface based on breaking out-of-plane symmetry, which may specifically include the following methods: (1) Out-of-plane height difference design: Two nanopillar structures with different heights are set in the same supercell to form asymmetry in the vertical direction; (2) Non-uniform material distribution: Introducing local material differences (such as covering part of the area with a hydrogel layer) into the interior or surface of the nanostructure to achieve out-of-plane optical property modulation; (3) The diameter (or length, width), height and interlayer spacing of the nanopillars in the metasurface structure are all subwavelength scales. By precisely controlling these parameters, robust quasi-continuous domain bound state resonance modes can be excited.
[0065] This invention modulates ambient humidity to excite robust quasi-continuous domain bound state resonance modes. Specifically, the dynamic regulation of this invention depends on the response of the humidity-driven deformable material layer to ambient humidity (external stimuli cause the humidity-driven deformable material layer to expand or contract in height). By altering the ambient refractive index through the humidity-driven deformable material layer's humidity-responsive swelling behavior, reversible out-of-plane symmetry breaking is induced, and the transition from continuous domain bound state to quasi-continuous domain bound state is actively controlled.
[0066] This invention, through the design of an out-of-plane symmetry-broken structure and the introduction of humidity-sensitive materials, enables quasi-continuous domain bound state manipulation across a broad ultraviolet to near-infrared spectral range. Furthermore, it exhibits low sensitivity to manufacturing errors and environmental disturbances, demonstrating good robustness. In addition, this invention offers advantages such as simple manufacturing process, reduced manufacturing costs, and multifunctional integration.
[0067] In summary, compared with traditional optical metasurfaces and quasi-continuous domain bound state manipulation techniques, the hybrid out-of-plane symmetry broken all-dielectric metasurface and quasi-continuous domain bound state manipulation techniques provided by this invention have the following advantages and beneficial effects: (1) Excellent robustness: Compared with the traditional in-plane symmetry broken structure, the metasurface provided by the present invention contains a humidity-driven deformation material layer. Since the height difference material used in the present invention is a humidity-sensitive material, it can dynamically control the height difference through the ambient humidity, exhibiting a significantly narrower linewidth and more stable resonance. Moreover, within a wide incident angle range, the quasi-continuous domain bound state can still maintain a stable Q factor, resonant wavelength and modulation depth. Therefore, it can reduce the sensitivity to manufacturing errors and environmental disturbances, slow down the Q value decay rate, and ensure the stability of the device in practical applications.
[0068] (2) Wideband adaptability: By optimizing out-of-plane parameters, the present invention can achieve quasi-continuous domain bound state modulation in a wide near-infrared spectral range.
[0069] (3) Simplified manufacturing process: Compared with multi-layer complex metal-dielectric structures, the present invention adopts an all-dielectric material system, which avoids the problem of metal loss and can be prepared by one-step photolithography process, significantly reducing manufacturing costs.
[0070] (4) Dynamic adjustability: The metasurface provided by the present invention contains a humidity-driven deformation material layer. By introducing environmentally responsive materials (such as hydrogels), the device performance can be adjusted in real time, breaking through the application limitations of traditional static metasurfaces.
[0071] In summary, this invention provides a novel optical metasurface structure that combines high robustness, multifunctionality, and miniaturization, offering a solution to the key challenge of achieving robust quasi-continuous bound states.
[0072] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A metasurface, characterized in that, The metasurface comprises a plurality of periodically arranged square lattice supercells; each square lattice supercell comprises a base layer, and a first nanopillar and a second nanopillar located on the base layer; the first nanopillar is a bilayer composite structure comprising a humidity-driven deformation material layer as the bottom and a first dielectric layer as the top. The second nanopillar is a single-layer structure, including a second dielectric layer; the first dielectric layer and the second dielectric layer have the same height; the metasurface dynamically adjusts the height difference between the first nanopillar and the second nanopillar based on the ambient humidity.
2. The metasurface according to claim 1, characterized in that, The first nanopillar is located at the center of the lattice point of the square lattice formed by the four second nanopillars, and the second nanopillar is located at the center of the lattice point of the square lattice formed by the four first nanopillars.
3. The metasurface according to claim 1, characterized in that, The dimensions of the first nanopillar, the second nanopillar, and the interlayer spacing between the first and second nanopillars are all subwavelength scales.
4. The metasurface according to claim 1, characterized in that, The humidity-driven deformation material layer is made of hydrogel, the first dielectric layer and the second dielectric layer are both made of silicon, and the substrate layer is made of silicon dioxide.
5. The metasurface according to claim 1, characterized in that, The humidity-driven deformable material layer, the first dielectric layer, and the second dielectric layer have the same planar shape and the same planar external profile dimensions.
6. The metasurface according to claim 5, characterized in that, The humidity-driven deformable material layer, the first medium layer, and the second medium layer are all cylinders with the same diameter; or, the humidity-driven deformable material layer, the first medium layer, and the second medium layer are all cuboids with the same width and length.
7. The metasurface according to claim 5, characterized in that, The quasi-continuous bound state resonance of the metasurface is insensitive to the incident angle; the quasi-continuous bound state resonance characteristics of the metasurface are highly stable when the asymmetry parameters change; the asymmetry parameters include the height of the humidity-driven deformation material layer and the external contour size of the plane; the quasi-continuous bound state resonance characteristics include the resonance wavelength, the quality factor, and the modulation depth at the resonance wavelength.
8. The metasurface according to claim 1, characterized in that, The metasurface can achieve quasi-continuous domain bound state manipulation over a wide spectral range from ultraviolet to near-infrared.
9. A refractive index sensor, characterized in that, Includes metasurfaces as described in any one of claims 1 to 8.
10. A method for realizing robust quasi-continuous bound states, characterized in that, Robust quasi-continuous domain bound states are realized based on the metasurface as described in any one of claims 1 to 8.