Metasurface structure, preparation method thereof and metasurface device

Abstract

The invention relates to the technical field of metasurface biosensing, in particular to a metasurface structure, a preparation method thereof and a metasurface device.The metasurface structure comprises a plurality of basic unit structures which are periodically arranged in the length direction and the width direction of the metasurface structure; at least one group of hole array is etched on the basic unit structure substrate, each group of hole array comprises two nanoimprint rectangular holes, and the two nanoimprint rectangular holes form opposite rotation angles in the width direction and are arranged in an axial symmetry manner in the length direction; and the metal layer covers the surface of the substrate and the bottom of the nanoimprint rectangular hole to form two layers of metal films so as to form a plasma resonance structure. Through the combination of the nanoimprint process and the rotational symmetry breaking design, a low-cost and tunable BIC metasurface device is realized, the limitation of traditional high-cost processing and a single resonant mode is solved, and the BIC metasurface device has a wide prospect in the fields of biosensing, spectrum detection, terahertz application and the like.

Description

Technical Field

[0001] The present invention relates to the field of supersurface biosensing technology, and in particular to a supersurface structure and a preparation method thereof, and a supersurface device. Background Art

[0002] In recent years, with the growing demand for health and disease monitoring, high-sensitivity, low-cost biodetection and identification technologies have received widespread attention. Optical biosensors, especially those based on optical metasurfaces, have become a research hotspot due to their subwavelength structure and strong light-matter interaction characteristics, showing the potential for highly sensitive and specific detection. Among them, plasmonic metasurfaces based on bound states in the continuum (BIC) are considered powerful tools for highly sensitive biosensing and terahertz applications due to their extremely high quality factors and tunable resonant modes. BIC was originally used to describe the highly localized state of electrons in potential barriers and has now been extended to the field of electromagnetic waves. Its unique localized modes exhibit extremely high Q factors (quality factors at resonance) and robustness, making them suitable for fields such as biomedicine, lasers, and spectral imaging.

[0003] However, existing BIC-based metasurface biosensors still face the following technical bottlenecks: 1. High preparation cost: Traditional methods rely on technologies such as electron beam lithography to achieve micro-nanoscale resonant structures. Although the processing accuracy is high, it is expensive and time-consuming, which limits its large-scale application.

[0004] 2. Single structural design: Metasurfaces prepared based on nanoimprint lithography (NIL) technology can usually only be designed as a single circular hole structure with full angle symmetry. The resonant mode is single and continuous tuning or multi-resonant modes cannot be achieved, making it difficult to meet the diverse needs of high-sensitivity sensing.

[0005] 3. Insufficient tuning capability: Existing metasurface devices are difficult to achieve continuous tuning of resonant modes by adjusting structural parameters, which limits their application potential in complex sensing scenarios.

[0006] To address the above issues, there is an urgent need for a low-cost, highly sensitive metasurface device design with multi-resonance mode tuning capabilities. Summary of the Invention

[0007] The present invention provides a metasurface structure and a preparation method thereof, and a metasurface device, which are used to solve the defects of BIC-based metasurface biosensors in the prior art, such as high preparation cost, single structural design, and insufficient tuning capability.

[0008] The present invention provides a metasurface structure, comprising a plurality of basic unit structures, wherein the plurality of basic unit structures are periodically arranged along the length and width directions of the metasurface structure, each of the basic unit structures comprises a substrate, a nanoimprinted rectangular hole and a metal layer, wherein at least one group of hole arrays is etched on the substrate, each group of the hole arrays comprises two nanoimprinted rectangular holes, the two nanoimprinted rectangular holes form opposite rotation angles in the width direction, and the two nanoimprinted rectangular holes are arranged axially symmetrically in the length direction; the metal layer covers the substrate surface and the bottom of the nanoimprinted rectangular holes to form a first metal film on the substrate surface and a second metal film on the bottom of the nanoimprinted rectangular holes, wherein the first metal film and the second metal film constitute a plasma resonance structure.

[0009] According to a metasurface structure provided by the present invention, the substrate is a silicon substrate or a silicon oxide substrate.

[0010] According to a super surface structure provided by the present invention, the metal layer is a gold film, and the thickness of the first metal film and the second metal film is 80nm~120nm.

[0011] According to a metasurface structure provided by the present invention, the rotation angle formed by the nano-imprinted rectangular hole in the width direction ranges from 0° to 42°.

[0012] According to a metasurface structure provided by the present invention, the length of the basic unit structure is 1.26μm~1.32μm; the width of the basic unit structure is 0.84μm~0.90μm; the hole length of the nanoimprinted rectangular hole is 0.64μm~0.70μm; the hole width of the nanoimprinted rectangular hole is 0.19μm~0.25μm; the hole depth of the nanoimprinted rectangular hole is 0.37μm~0.43μm; and the center distance between two nanoimprinted rectangular holes is 0.61μm~0.67μm.

[0013] According to a metasurface structure provided by the present invention, the metasurface structure forms at least two resonance modes in the mid-infrared band, including a first resonance mode and a second resonance mode.

[0014] The first resonant mode is formed in a wavelength band ranging from 2800nm to 2950nm, and the electromagnetic field energy resonates along the width direction in the area between the first metal film and the second metal film; the second resonant mode is formed in a wavelength band ranging from 3950nm to 4050nm, and the electromagnetic field energy resonates along the length direction in the area between the first metal film and the second metal film.

[0015] According to a metasurface structure provided by the present invention, the metasurface structure is suitable for achieving continuous tuning of the resonant mode by changing the size of the rotation angle formed by the nanoimprinted rectangular hole in the width direction, and the peak-to-peak value and line width of the resonance increase with the increase of the rotation angle, and the quality factor at resonance decreases with the increase of the rotation angle.

[0016] According to a metasurface structure provided by the present invention, the metasurface structure is suitable for achieving continuous tuning of the resonant mode by changing the angle of incident light, and the angle of incident light is 0°~30°.

[0017] The present invention also provides a method for preparing a supersurface structure, which is suitable for preparing any of the above-mentioned supersurface structures, and the method for preparing the supersurface structure comprises: A periodically arranged hole array is etched on the surface of the substrate by a nanoimprint process, each of the hole arrays includes two nanoimprinted rectangular holes, and the two nanoimprinted rectangular holes are arranged axially symmetrically in the length direction of the substrate and form opposite rotation angles in the width direction of the substrate.

[0018] Metal is deposited on the substrate by magnetron sputtering or evaporation to form a first metal film on the substrate surface and a second metal film at the bottom of the nano-imprinted rectangular hole to form a plasma resonance structure.

[0019] Symmetry breaking is achieved by adjusting the nanoimprint process template design and changing the rotation angle of the nanoimprint rectangular hole.

[0020] The present invention also provides a metasurface device, comprising any one of the metasurface structures described above, wherein the metasurface device is suitable for use in biomolecule detection, spectral imaging or terahertz sensing.

[0021] The metasurface structure provided by this invention consists of a substrate with two axisymmetric nanoimprinted rectangular apertures with opposite rotation angles, and two different gold films (a first metal film and a second metal film) arranged in the Z direction, forming a single basic unit structure. These films are periodically arranged in the X and Y directions to form the metasurface structure. By combining a nanoimprint process with a rotational symmetry-breaking design and incident angle control, a low-cost, tunable BIC metasurface device is realized, overcoming the limitations of traditional high-cost processing and a single resonant mode. This device holds great promise in fields such as biosensing, spectral detection, and terahertz applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 It is a schematic diagram of the axonometric structure of the metasurface structure provided by the present invention.

[0024] Figure 2 It is a schematic diagram of the surface structure of the super surface structure provided by the present invention.

[0025] Figure 3 yes Figure 2 AA cross-sectional structure diagram.

[0026] Figure 4 This is a schematic diagram of the reflection spectrum distribution of the first resonance mode when simulating the rotation angle change of the nanoimprinted rectangular hole.

[0027] Figure 5 This is the cross-sectional electric field distribution diagram of two nanoimprinted rectangular holes at the resonance peak.

[0028] Figure 6 It is the planar electric field distribution diagram of two nanoimprinted rectangular holes at the resonance peak.

[0029] Figure 7 This is a schematic diagram of the reflection spectrum distribution of the second resonance mode when simulating the rotation angle change of the nanoimprinted rectangular hole.

[0030] Figure 8 It simulates the change in the reflection spectrum of the first resonance mode caused by the change in the rotation angle of the nanoimprinted rectangular hole when the incident light angle is 12°.

[0031] Figure 9 It simulates the change in the reflection spectrum of the second resonance mode caused by the change in the rotation angle of the nanoimprinted rectangular hole when the incident light angle is 12°.

[0032] Figure 10 It simulates the change in the reflection spectrum of the first resonance mode caused by the change in the angle of incident light when the rotation angle of the nanoimprinted rectangular hole is 24°.

[0033] Figure 11 It simulates the reflection spectrum change of the second resonance mode caused by the change of incident light angle when the rotation angle of the nanoimprinted rectangular hole is 24°.

[0034] Reference numerals: 1. Substrate; 2. Nanoimprinted rectangular hole; 3. Metal layer; 31. First metal film; 32. Second metal film. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0036] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0037] In the embodiments of the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," or "above" a second feature may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," or "below" a second feature may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0038] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0039] The following combination Figures 1 to 11 The present invention describes the super surface structure and its preparation method, and the super surface device.

[0040] One embodiment of the present invention provides a metasurface structure, which includes a plurality of basic unit structures, and the plurality of basic unit structures are periodically arranged along the length direction and the width direction of the metasurface structure, respectively. Figure 1 As shown, each basic unit structure includes a substrate 1, a nanoimprinted rectangular hole 2 and a metal layer 3. At least one group of hole arrays is etched on the substrate 1, and each group of hole arrays includes two nanoimprinted rectangular holes 2. The two nanoimprinted rectangular holes 2 form opposite rotation angles in the width direction, and the two nanoimprinted rectangular holes 2 are arranged axially symmetrically in the length direction; the metal layer 3 covers the surface of the substrate 1 and the bottom of the nanoimprinted rectangular hole 2 to form a first metal film 31 on the surface of the substrate 1 and a second metal film 32 at the bottom of the nanoimprinted rectangular hole 2. The first metal film 31 and the second metal film 32 constitute a plasma resonance structure.

[0041] Combine Figure 2 and Figure 3 As shown, the metasurface structure of this embodiment consists of a substrate 1 with two axisymmetric nanoimprinted rectangular holes 2, each with opposite rotation angles, and two different gold films (a first metal film 31 and a second metal film 32) in the Z direction, forming a single basic unit structure. These are periodically arranged in the X and Y directions to form the metasurface structure. The core of this embodiment is to design a low-cost metasurface structure based on nanoimprint lithography (NIL). By introducing rotational symmetry breaking and incident angle control, a tunable resonant mode of bounded states in the continuous domain (BIC) is achieved.

[0042] Specifically, the nanoimprinted rectangular holes 2 are fabricated using a nanoimprinting process (NIL), which changes the high-cost electron beam lithography technology limitations of existing metasurface-based continuous domain bound state sensing strategies, providing a powerful solution for low-cost, highly sensitive biosensing applications. The two nanoimprinted rectangular holes 2 form opposite rotation angles in the width direction to achieve symmetry breaking. It should be understood that when the symmetry is not broken (rotation angle ), the BIC mode is the "dark mode", which does not couple with the incident light and shows an extremely high Q factor. The BIC mode gradually transforms into an observable “bright mode”, forming a narrow-band resonance peak, and the two nanoimprinted rectangular holes 2 rotate around their own centers by ± (achieved by adjusting the nanoimprint process template design), by changing ( ), breaking the structural symmetry and achieving continuous tuning of the resonant mode, affecting the Q factor and line width. Furthermore, by adjusting the incident light angle ( ), further breaking symmetry, splitting or shifting the resonant mode, and enhancing sensing adaptability. The metasurface structure of this embodiment, through nanoimprinting combined with a rotational symmetry-breaking design, achieves a low-cost, tunable BIC metasurface device. This overcomes the limitations of traditional high-cost processing and a single resonant mode, and holds broad promise in fields such as biosensing, spectral detection, and terahertz applications.

[0043] In some embodiments of the metasurface structure of the present invention, substrate 1 is a silicon substrate or a silicon oxide substrate. Compared to silicon substrates (refractive index 3.4) and silicon oxide substrates (refractive index 1.45), silicon oxide substrates exhibit lower optical loss and sharper resonance peaks in the 2800-4050 nm wavelength band. Silicon oxide substrates can also reduce light absorption, improve the Q factor of the resonance mode (experimentally measured to be >500), and increase sensitivity by 30%.

[0044] The metal layer 3 can be a gold film. The thickness of the first metal film 31 and the second metal film 32 is 80nm~120nm, preferably 100nm. A gold film that is too thin (less than 80nm) will result in insufficient plasma resonance intensity, while a gold film that is too thick (greater than 120nm) will increase the cost and reduce the field localization. Experiments show that the resonance intensity of an 80nm thick gold film is 850a.u., and the electric field enhancement factor is , the resonance intensity of a 100nm thick gold film is 1200a.u., and the electric field enhancement factor is , the resonance intensity of the 120nm thick gold film is 1100a.u., and the electric field enhancement factor is Therefore, the 100 nm gold film achieves the best surface plasmon polaritons (SPP) coupling in the infrared band, and the electric field enhancement factor reaches .

[0045] The rotation angle of the nanoimprinted rectangular hole 2 in the width direction ranges from 0° to 42°. The simulation analysis based on the simulation software shows that the rotation angle When , there is no resonance peak (pure BIC dark mode). By changing the rotation angle, the reflection spectrum changes and resonance mode distribution when different asymmetric factors are introduced can be realized. When the rotation angle is 0.01, the metasurface structure forms at least two resonance modes in the mid-infrared band. In the 2870nm band, the resonance peak line width is 8nm, and the quality factor at resonance is 360. In the 4020nm band, the resonance peak line width is 12nm, and the quality factor at resonance is 335. When the resonance peak is red-shifted and broadened (the resonance peak line width increases to 18nm), it is suitable for wide spectrum detection, and the quality factor at resonance can be reduced to 200. ( ), which can achieve continuous tuning of the resonant mode to meet the needs of different sensing scenarios (such as narrowband detection or wide-spectrum monitoring).

[0046] The length of the basic unit structure is 1.26μm to 1.32μm; the width of the basic unit structure is 0.84μm to 0.90μm; the length of the nanoimprinted rectangular hole 2 is 0.64μm to 0.70μm; the width of the nanoimprinted rectangular hole 2 is 0.19μm to 0.25μm; the depth of the nanoimprinted rectangular hole 2 is 0.37μm to 0.43μm; and the center-to-center spacing between the two nanoimprinted rectangular holes 2 is 0.61μm to 0.67μm. A preferred configuration is a basic unit structure with a length of 1.29μm and a width of 0.87μm, a nanoimprinted rectangular hole 2 with a length of 0.67μm, a width of 0.22μm, and a depth of 0.4μm, and a center-to-center spacing of 0.64μm, for the highest resonant mode coupling efficiency.

[0047] In some embodiments of the metasurface structure of the present invention, the metasurface structure forms at least two resonant modes in the mid-infrared band, including a first resonant mode and a second resonant mode. The first resonant mode is formed in the wavelength range of 2800nm to 2950nm, and the electromagnetic field energy resonates along the width direction in the region between the first metal film 31 and the second metal film 32. The second resonant mode is formed in the wavelength range of 3950nm to 4050nm, and the electromagnetic field energy resonates along the length direction in the region between the first metal film 31 and the second metal film 32.

[0048] It can be understood that by imprinting two nano-imprinted rectangular holes 2 on the substrate 1, the hole area formed is asymmetric with other areas, the energy is confined to the hole area to produce interference destructiveness, and periodic perturbations are introduced into the system, so that the dark mode that originally does not interact with the incident light and does not radiate has a radiation channel.

[0049] In some embodiments of the metasurface structure of the present invention, the metasurface structure is suitable for achieving continuous tuning of the resonant mode by changing the size of the rotation angle formed by the nanoimprinted rectangular hole 2 in the width direction, and the peak value and line width of the resonance increase with the increase of the rotation angle, and the quality factor at resonance decreases with the increase of the rotation angle.

[0050] It can be understood that the length of the basic unit structure is selected to be 1.29μm, the width is 0.87μm, the hole length of the nanoimprinted rectangular hole 2 is 0.67μm, the hole width is 0.22μm, the hole depth is 0.4μm, and the center distance between the two nanoimprinted rectangular holes 2 is 0.64μm. The simulation software is used for simulation analysis to explore the changes in the reflection spectrum and the distribution of the resonance mode when different asymmetric factors are introduced. Based on the simulation analysis of the simulation software, the incident light is simulated as TM mode incident (parallel to the Y direction), the surrounding medium is set to vacuum, the periodic boundary conditions are considered in the X and Y directions, and an XY / XZ surface monitor is placed at the center of the structure to detect the energy distribution of the electromagnetic field confined to the basic unit structure. Introducing the structural rotation angle Changing from 0° to 42°, the structural symmetry is gradually broken, and the reflection spectrum change of the basic unit structure of the metasurface structure is measured at the same time. The results show obvious continuous domain bound state change characteristics, and two resonance modes are presented in the mid-infrared spectrum range, namely the first resonance mode and the second resonance mode, respectively. Figure 4 and Figure 7 As shown. Keep other parameters unchanged and only increase the rotation angle , it can be seen that the original uniform reflection spectrum gradually presents a resonance peak with a gradually increasing line width, which is reflected in the first resonance mode and the second resonance mode. The first resonance mode is mainly distributed in the wavelength range of 2800nm to 2950nm, and the electromagnetic wave energy is limited to the region between the first metal film 31 and the second metal film 32 and resonates along the width direction (Y direction); the second resonance mode is mainly distributed in the wavelength range of 3950nm to 4050nm, and the electromagnetic wave energy is limited to the region between the first metal film 31 and the second metal film 32 and resonates along the width direction (X direction). When the rotation angle As the value gradually decreases, the coupling between the discrete mode and the continuous mode also decreases, so the small linewidth also brings a higher resonance factor, such as Figure 5 and Figure 6 The XY / XZ surface monitoring results shown in the figure show a significant resonant enhancement in the XY plane, with the electric field distributions of the two different apertures exhibiting opposite phases, consistent with the characteristics of a continuum bound-state resonant mode. The confined enhanced electric field is primarily localized at the edge of the first metal film 31 above the nanoimprinted rectangular aperture 2 and at the second metal film 32 at the bottom of the nanoimprinted rectangular aperture 2, significantly increasing the chance of interaction with the biomolecule being detected, which facilitates the realization of highly sensitive sensing.

[0051] In actual testing situations, the incident light of optical sensing tests in the mid-infrared band often carries a certain range of incident azimuth angles, so the electromagnetic waves responded by the metasurface device may not be In some other embodiments of the metasurface structure of the present invention, the metasurface structure is suitable for achieving continuous tuning of the resonant mode by changing the angle of incident light, and the angle of incident light is 0°~30°. The incident angle is further changed in the simulation to continue to introduce asymmetric breaking of the structure.

[0052] See also Figure 8 and Figure 9 As shown, in the case of oblique incidence ( ) Continuously change the rotation angle of the structure itself The reflection spectra of the first and second resonance modes are obtained when Figure 8 and Figure 9 It can be seen that with the deflection of the incident angle, the incident asymmetry factor introduces more resonant components to the original resonant mode of the structure, and the original first resonant mode shows a splitting trend and the overall spectrum redshifts. However, similar to the case of vertical incidence, as the structure itself gradually introduces symmetry breaking rotation angle The spectrum also shows a continuous tuning transition change, and the resonance peak value and line width gradually increase with the increase of the rotation angle, and the quality factor at resonance decreases accordingly.

[0053] Since the nanoimprinted rectangular hole 2 has the structural asymmetry feature in the Z direction, when the special case of oblique incidence is expanded, the incident angle is gradually broken. When the symmetry of is broken, discrete continuous domain bound state modes will appear in the dark mode distribution that originally coherently cancels each other at vertical incidence. Figure 10 and Figure 11 As shown, at a fixed structure rotation angle unchanged, and when gradually from vertical incidence ( ) changes to oblique incidence ( ), there is an obvious transition between the first resonance mode and the second resonance mode near 2900nm and 4000nm, showing the splitting of a single continuous domain bound state mode. Therefore, the metasurface structure of this embodiment can respond to asymmetric breaking in two different dimensions and show corresponding BIC resonance peaks, which has significant optical application range and biosensing potential.

[0054] On the other hand, the present invention provides a method for preparing a metasurface structure, which is suitable for preparing the metasurface structure in any of the above-mentioned embodiments or examples. In some specific embodiments, the method for preparing the metasurface structure includes the following: selecting a high-purity substrate 1 (silicon oxide substrate, 4 inches in diameter), cleaning it according to RCA standards, and then drying it. Using a prefabricated nickel template (containing a designed nanoimprint rectangular hole 2 pattern), hot stamping is performed at 180°C and 5MPa for 30 seconds, and the imprinted pattern is filled with UV curing glue (NOA61). After UV curing, the mold is demolded and a periodically arranged hole array is etched on the surface of the substrate 1. Each hole array includes two nanoimprint rectangular holes 2. The two nanoimprint rectangular holes 2 are arranged axially symmetrically in the length direction of the substrate 1 and form opposite rotation angles in the width direction of the substrate 1. A 100nm gold film is deposited using an electron beam evaporation coating machine (magnetron sputtering can also be used) at a rate of 0.5Å / s and a vacuum degree of 5×10 -6 Torr, ion beam etching removes excess metal, preserving the metal layer at the bottom and surface of the hole. The deposited gold film forms a first metal film 31 on the surface of substrate 1, and a second metal film 32 at the bottom of the nanoimprinted rectangular hole 2, forming a plasmon resonance structure. Symmetry breaking is achieved by adjusting the design of the nickel template prefabricated in the nanoimprint process and changing the rotation angle of the nanoimprinted rectangular hole 2.

[0055] It can be understood that the preparation method of the metasurface structure of this embodiment uses a nanoimprint process to design a mid-infrared metasurface structure with a high resonance factor to achieve a continuous domain bound state. The prepared metasurface structure can have multiple BIC resonance modes, and the bound state characteristics are verified by breaking the rotation angle symmetry and incident angle symmetry of the nanoimprinted rectangular hole 2. With the help of a low-cost, high-precision metasurface structure preparation paradigm, a large number of BIC device preparation and biosensing can be achieved quickly and conveniently. The preparation method of the metasurface structure of this embodiment changes the high-cost electron beam lithography technology limitations of the existing metasurface-based continuous domain bound state sensing strategy, and provides a powerful solution for low-cost, highly sensitive biosensing applications; it broadens the optical application range and sensing potential of the existing metasurface devices prepared based on nanoimprint technology, and on the basis of the design of the resonance mode and metasurface structure, realizes a continuous domain bound state nanoimprint metasurface structure with continuous tuning in the mid-infrared band.

[0056] Another aspect of the present invention provides a metasurface device. The metasurface device of the present invention includes the metasurface structure of any of the above embodiments or examples. In combination with the description of the metasurface structure in the above embodiments, the metasurface device of the present invention has multiple resonant modes, enabling it to produce multiple resonant peak responses to incident light in the mid-infrared band, and each resonant mode has two continuous tuning dimensions and can produce corresponding continuous responses to the introduced structural rotation angle and incident angle violations. At the same time, each resonant mode has a high resonance factor, can fully produce coherent coupling with the ambient medium, and has high sensing potential. The metasurface device is suitable for use in biomolecule detection, spectral imaging, or terahertz sensing.

[0057] It is understood that the metasurface device of the present invention achieves tunable continuous domain bound states by constructing on-chip resonant modes, thus providing a powerful alternative for low-cost and high-efficiency sensing strategies. By combining nanoimprinting technology with a rotational symmetry-breaking design, a low-cost, tunable BIC metasurface device is realized, overcoming the limitations of traditional high-cost processing and a single resonant mode. The metasurface device of the present invention has broad prospects in applications such as biomolecule detection, spectral imaging, and terahertz sensing.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A metasurface structure, characterized in that: The metasurface structure comprises a plurality of basic unit structures, each of which is periodically arranged along the length direction and the width direction of the metasurface structure. A substrate (1), wherein at least one group of hole arrays is etched on the substrate (1), each group of the hole arrays comprises two nano-imprinted rectangular holes (2), the two nano-imprinted rectangular holes (2) form opposite rotation angles in the width direction, and the two nano-imprinted rectangular holes (2) are arranged in an axisymmetric manner in the length direction; A metal layer (3) covers the surface of the substrate (1) and the bottom of the nanoimprinted rectangular hole (2) to form a first metal film (31) on the surface of the substrate (1) and a second metal film (32) at the bottom of the nanoimprinted rectangular hole (2), wherein the first metal film (31) and the second metal film (32) constitute a plasma resonance structure.

2. The metasurface structure according to claim 1, wherein The substrate (1) is a silicon substrate or a silicon oxide substrate.

3. The metasurface structure according to claim 1, wherein: The metal layer (3) is a gold film, and the thickness of the first metal film (31) and the second metal film (32) is 80 nm to 120 nm.

4. The metasurface structure according to claim 1, wherein The rotation angle formed by the nano-imprinted rectangular hole (2) in the width direction ranges from 0° to 42°.

5. The metasurface structure according to claim 1, wherein: The length of the basic unit structure is 1.26 μm to 1.32 μm; the width of the basic unit structure is 0.84 μm to 0.90 μm; the hole length of the nanoimprinted rectangular hole (2) is 0.64 μm to 0.70 μm; the hole width of the nanoimprinted rectangular hole (2) is 0.19 μm to 0.25 μm; the hole depth of the nanoimprinted rectangular hole (2) is 0.37 μm to 0.43 μm; and the center distance between two nanoimprinted rectangular holes (2) is 0.61 μm to 0.67 μm.

6. The metasurface structure according to any one of claims 1 to 5, characterized in that The metasurface structure forms at least two resonance modes in the mid-infrared band, including a first resonance mode and a second resonance mode; The first resonant mode is formed in a wavelength range of 2800nm to 2950nm, and the electromagnetic field energy resonates along the width direction in the region between the first metal film (31) and the second metal film (32); the second resonant mode is formed in a wavelength range of 3950nm to 4050nm, and the electromagnetic field energy resonates along the length direction in the region between the first metal film (31) and the second metal film (32).

7. The metasurface structure according to claim 6, wherein: The metasurface structure is suitable for achieving continuous tuning of the resonance mode by changing the size of the rotation angle formed by the nanoimprinted rectangular hole (2) in the width direction, and the resonance peak value and line width increase with the increase of the rotation angle, and the quality factor at resonance decreases with the increase of the rotation angle.

8. The metasurface structure according to claim 6, wherein: The metasurface structure is suitable for achieving continuous tuning of the resonant mode by changing the incident light angle, and the incident light angle is 0°~30°.

9. A method for preparing a super surface structure, characterized in that: Suitable for preparing the super surface structure according to any one of claims 1 to 8, the preparation method of the super surface structure comprising: A periodically arranged hole array is etched on the surface of a substrate (1) by a nanoimprint process, each hole array comprising two nanoimprinted rectangular holes (2), the two nanoimprinted rectangular holes (2) being arranged axially symmetrically in the length direction of the substrate (1) and forming opposite rotation angles in the width direction of the substrate (1); A metal is deposited on the substrate (1) by magnetron sputtering or evaporation, wherein the metal forms a first metal film (31) on the surface of the substrate (1), and the metal forms a second metal film (32) at the bottom of the nanoimprinted rectangular hole (2), thereby forming a plasma resonance structure; Symmetry breaking is achieved by adjusting the nanoimprint process template design and changing the rotation angle of the nanoimprint rectangular hole (2).

10. A metasurface device, characterized in that: The metasurface structure comprises the metasurface structure described in any one of claims 1 to 8, wherein the metasurface device is suitable for use in biomolecule detection, spectral imaging or terahertz sensing.

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