Tunable dielectric metasurfaces with near-infrared non-Hermitian singularities

Abstract

This invention provides a tunable dielectric metasurface with a near-infrared non-Hermitian singularity. The tunable dielectric metasurface with a near-infrared non-Hermitian singularity, operating in the near-infrared band, not only achieves dynamic control of the non-Hermitian singularity but also systematically exhibits singularity characteristics such as state transition, topological phase protection, strong chirality, and phase abrupt change.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano photonics technology, specifically relating to a tunable dielectric metasurface for near-infrared non-Hermitian singularities. Background Technology

[0002] Currently, the realization of polarization-modulated non-Hermitian exceptional points (EPs) is mostly limited to metasurface platforms based on metallic materials to achieve terahertz band frequencies. That is, existing non-Hermitian metasurfaces operating on EPs are mostly based on metallic materials, with their operating band concentrated in the terahertz frequency range. Furthermore, metals exhibit significant ohmic losses in the near-infrared band, preventing direct extension to this band. Due to the extremely high absorption characteristics of terahertz waves for water-containing samples, these devices are difficult to integrate with liquid-phase biochemical environments, preventing the unique physical effects of exceptional points, such as high sensitivity and chiral selectivity, from being effectively utilized in real-world biological detection scenarios. This restricts the comprehensive exploration of the physical phenomena of EPs on a broader optical platform and severely limits their practical application in the field of biochemical sensing. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings and deficiencies of the prior art and provide a tunable dielectric metasurface with a near-infrared non-Hermitian singularity. The tunable dielectric metasurface with a near-infrared non-Hermitian singularity, which operates in the near-infrared band, not only realizes the dynamic control of non-Hermitian singularities, but also systematically exhibits singularity characteristics such as state transition, topological phase protection, strong chirality, and phase abrupt change.

[0004] This invention is achieved through the following technical solution:

[0005] A tunable dielectric metasurface with near-infrared non-Hermitian singularities includes a silicon dioxide substrate and a plurality of non-Hermitian singularity units. The silicon dioxide substrate comprises a plurality of substrate units. The plurality of non-Hermitian singularity units are periodically arranged on the silicon dioxide substrate. Each non-Hermitian singularity unit includes a silicon dielectric open-circuit resonator and a germanium dielectric open-circuit resonator disposed on a single substrate unit. The silicon dielectric open-circuit resonator and the germanium dielectric open-circuit resonator are located in the same plane. The silicon dielectric open-circuit resonator and the germanium dielectric open-circuit resonator are arranged perpendicularly to each other. The silicon dielectric open-circuit resonator is arranged along the x-axis direction, and the silicon dielectric open-circuit resonator has a first [missing information] arranged along the x-axis direction. The resonant ring has an opening, the length of which is not less than the width of the silicon dielectric resonant ring; the first opening is positioned away from the germanium dielectric open-ring resonant ring; a graphene layer is disposed on one side of the silicon dielectric open-ring resonant ring, the graphene layer covering the first opening; the germanium dielectric open-ring resonant ring is positioned along the y-axis and is located to the right of the silicon dielectric open-ring resonant ring; the germanium dielectric open-ring resonant ring has a second opening along the y-axis, the length of which is not less than the width of the germanium dielectric open-ring resonant ring; the opening directions of the first opening and the second opening are orthogonal; the resonant wavelengths of the silicon dielectric open-ring resonant ring and the germanium dielectric open-ring resonant ring are close to the degenerate region.

[0006] The tunable dielectric metasurface for near-infrared non-Hermitian singularities provided by this invention utilizes coupled-mode theory and the equivalent "virtual gain" method. It constructs a PT-symmetric system by building silicon and germanium dielectric open-circuit resonators to achieve the PT symmetry conditions required for non-Hermitian singularities, thereby establishing a PT symmetric system. Tunable non-Hermitian singularities are achieved by controlling the incident wavelength and the parameter space of the graphene Fermi level. This tunable dielectric metasurface for near-infrared non-Hermitian singularities, operating in the near-infrared band, not only achieves dynamic control of non-Hermitian singularities but also systematically exhibits singularity characteristics such as state transitions, topological phase protection, strong chirality, and phase abrupt changes.

[0007] Furthermore, the thickness t of both the silicon dielectric open-circuit resonator and the germanium dielectric open-circuit resonator is 110 nm; the center positions of the silicon dielectric open-circuit resonator and the germanium dielectric open-circuit resonator are 361 nm apart in the x-axis direction and 124 nm apart in the y-axis direction; the outer diameter L1 of the silicon dielectric open-circuit resonator is 363 nm, the width L2 of the silicon dielectric open-circuit resonator is 111.5 nm, and the width L3 of the first opening is 110 nm; the outer diameter L5 of the germanium dielectric open-circuit resonator is 300 nm, the width L6 of the germanium dielectric open-circuit resonator is 80 nm, and the width L7 of the second opening is 100 nm.

[0008] Furthermore, the non-Hermitian singularity unit is embedded in the base unit.

[0009] Furthermore, the substrate unit corresponds to a side length Px of 750 nm along the x-axis for the silicon dielectric open-circuit resonator; the substrate unit corresponds to a side length Py of 750 nm along the y-axis for the germanium dielectric open-circuit resonator.

[0010] Furthermore, the Fermi level of the graphene layer can be tuned from 0 to 0.6 eV.

[0011] The present invention also provides the application of the above-mentioned tunable dielectric metasurface with near-infrared non-Hermitian singularity in the field of sensing.

[0012] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the tunable dielectric metasurface of the near-infrared non-Hermitian singularity in Example 1.

[0014] Figure 2 This is a schematic diagram of the structure of the non-Hermitian singularity unit in Example 1.

[0015] Figure 3 This is a schematic diagram showing the position of the graphene layer in Example 1.

[0016] Figure 4 The intrinsic transmittance and amplitude phase spectra of graphene in Example 1 at different Fermi levels are shown.

[0017] Figure 5 The amplitude and phase of the eigenvalues ​​in Example 1 are Riemann surfaces in the parameter space (λ,Ge(y)).

[0018] Figure 6 This is a schematic diagram of the evolution of the polarization state in Example 1.

[0019] Figure 7 This is the transmission spectrum of the metasurface in Example 1. Detailed Implementation

[0020] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit the scope of the invention. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the embodiments of the present invention, and not all structures.

[0021] Furthermore, the terms "first," "second," "third," etc., used in the specification and claims are only for the purpose of distinguishing the description of the same technical features and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated, nor necessarily the order of description or chronological sequence. Where appropriate, the terms are interchangeable. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature.

[0022] Similarly, the terms "fixed" and "connected" are used in the specification and claims and should not be construed as limited to a direct connection. Therefore, the expression "device A is connected to device B" should not be limited to device A being directly connected to device B in a device or system; it means that there is a path between device A and device B, which can be a path that includes other devices or tools.

[0023] Example 1 This embodiment provides a tunable dielectric metasurface with a near-infrared non-Hermitian singularity. Figure 1 This is a schematic diagram of a tunable dielectric metasurface at a near-infrared non-Hermitian singularity. Figure 2 This is a schematic diagram of the structure of a non-Hermitian singularity unit, in which, Figure 2 (a) is a schematic diagram of the structure of silicon dielectric open-circuit resonator 21 and germanium dielectric open-circuit resonator 22. Figure 2 (b) is a top view of non-Hermitian singularity unit 2. Figure 3 This is a schematic diagram showing the location of the graphene layers. Please refer to it. Figures 1-3The near-infrared non-Hermitian singularity tunable dielectric metasurface includes a silicon dioxide substrate 1 and a plurality of non-Hermitian singularity units 2; the silicon dioxide substrate 1 includes a plurality of substrate units 11; the plurality of non-Hermitian singularity units 2 are periodically arranged on the silicon dioxide substrate 1; each non-Hermitian singularity unit 2 includes a silicon dielectric open-circuit resonant ring 21 and a germanium dielectric open-circuit resonant ring 22 disposed on a single substrate unit 11; the silicon dielectric open-circuit resonant ring 21 and the germanium dielectric open-circuit resonant ring 22 are located in the same plane; the silicon dielectric open-circuit resonant ring 21 and the germanium dielectric open-circuit resonant ring 22 are arranged perpendicularly to each other; the silicon dielectric open-circuit resonant ring 21 is arranged along the x-axis direction, and the silicon dielectric open-circuit resonant ring 21 is provided with a first [missing information] along the x-axis direction. The first opening 23 has a length not less than the width of the silicon dielectric open-ended resonant ring 21; the first opening 23 is positioned away from the open-ended germanium dielectric resonant ring 22; a graphene layer 25 is disposed on one side of the silicon dielectric open-ended resonant ring 21, covering the first opening 23; the germanium dielectric open-ended resonant ring 22 is positioned along the y-axis and is located to the right of the silicon dielectric open-ended resonant ring 21; the germanium dielectric resonant ring 22 has a second opening 24 along the y-axis, the length of the second opening 24 being not less than the width of the germanium dielectric resonant ring 22; the opening directions of the first opening 23 and the second opening 24 are orthogonal; the resonant wavelengths of the silicon dielectric open-ended resonant ring 21 and the germanium dielectric open-ended resonant ring 22 are close to the degenerate region.

[0024] This embodiment demonstrates the observation of non-Hermitian topological effects such as eigenstate exchange, phase abrupt change, and strong chirality in the neighborhood of a singular point. Specifically, the π-phase abrupt change in cross-polarized transmission is generated by the accumulation of geometric phases around the singular point, exhibiting topological robustness and dynamic control through graphene Fermi levels. This characteristic can be applied to near-infrared polarization control, biosensing, optical storage, and secure communication.

[0025] This embodiment provides a tunable dielectric metasurface for near-infrared non-Hermitian singularities. Based on coupled-mode theory and the equivalent "virtual gain" method, the PT symmetry conditions required for non-Hermitian singularities are achieved by constructing a silicon dielectric open-circuit resonator 21 and a germanium dielectric open-circuit resonator 22, thereby constructing a PT symmetric system. Tunable non-Hermitian singularities are realized by adjusting the incident wavelength and the parameter space of the graphene Fermi level. This embodiment's tunable dielectric metasurface for near-infrared non-Hermitian singularities operates as a dielectric metasurface device in the near-infrared band. It not only achieves dynamic control of non-Hermitian singularities but also systematically exhibits singularity characteristics such as state transitions, topological phase protection, strong chirality, and phase abrupt changes.

[0026] Please see Figures 1-2In this embodiment, the thickness t of both the silicon dielectric resonant ring 21 and the germanium dielectric resonant ring 22 is 110 nm; the center positions of the silicon dielectric resonant ring and the germanium dielectric resonant ring are 361 nm apart in the x-axis direction and 124 nm apart in the y-axis direction; the outer diameter L1 of the silicon dielectric resonant ring 21 is 363 nm, the width L2 of the silicon dielectric resonant ring 21 is 111.5 nm, and the width L3 of the first opening 23 is 110 nm; the outer diameter L5 of the germanium dielectric resonant ring 22 is 300 nm, the width L6 of the germanium dielectric resonant ring 22 is 80 nm, and the width L7 of the second opening 24 is 100 nm.

[0027] In this embodiment, the length of the first opening 23 is not less than the width of the silicon dielectric open-loop resonator 21, and the central axis of the first opening 23 passes through the center of the silicon dielectric open-loop resonator 21. In one embodiment, the length L4 of the first opening 23 is 170 nm. The length of the second opening 24 is not less than the width of the germanium dielectric open-loop resonator 22, and the central axis of the second opening 24 passes through the center of the silicon dielectric open-loop resonator 21. In one embodiment, the length L8 of the second opening 24 is 140 nm.

[0028] Please see Figures 1-2 In this embodiment, the non-Hermitian singularity unit 2 is embedded in the base unit 11.

[0029] Please see Figures 1-2 In this embodiment, the substrate unit 11 corresponds to the side length Px of the silicon dielectric open-ended resonant ring 21 along the x-axis, which is 750 nm; the substrate unit 11 corresponds to the side length Py of the germanium dielectric open-ended resonant ring 22 along the y-axis, which is 750 nm.

[0030] In this embodiment, the Fermi level of graphene layer 25 is tunable from 0 to 0.6 eV. In this embodiment, graphene layer 25 is a single-layer graphene structure.

[0031] In this embodiment, a silicon dielectric resonant ring 21 and a germanium dielectric open resonant ring 22 are embedded in the substrate unit 11 of a silicon dioxide substrate 1. The refractive index of silicon dioxide is 1.414. By constructing silicon dielectric resonant rings 21 and germanium dielectric open resonant rings 22 of different materials and sizes, the PT symmetry condition to be satisfied by the non-Hermitian singularity is achieved. By adjusting the spacing between the two open rings, a suitable distance (center position) between the two open rings is found. Then, by adjusting the Fermi level of the graphene covering the opening of the silicon open ring, the non-Hermitian singularity (EP) is found through dynamic control.

[0032] In the tunable dielectric metasurface provided in this embodiment, the existence of non-Hermitian singularities needs to be determined based on the intrinsic amplitude and phase angle. The transmission matrix is ​​a complex matrix, and its transmission is not the transmittance obtained in the usual way, but rather the transmission coefficient. To obtain the transmission coefficient, FDTD simulation software is first used to set boundary conditions for a specific structure, and then a plane wave of the corresponding band is input. Next, the electric field needs to be integrated, and then combined with the unstructured (background) electric field for data processing to obtain the four matrix elements of the transmission matrix corresponding to the four transmission coefficients. Finally, the characteristic amplitude spectrum and the phase spectrum are plotted for observation. Based on the state transition characteristics at EP, the position of the corresponding state is plotted on a Poincaré sphere, and the state transition is observed by tracing the evolution process of one of the states, thereby verifying that the tunable dielectric metasurface provided in this embodiment has non-Hermitian singularities.

[0033] In the tunable dielectric metasurface with near-infrared non-Hermitian singularities provided in this embodiment, the operating wavelength of the non-Hermitian singularities is extended to the near-infrared band, and a singularity is successfully realized at λ=1.1599μm, achieving dynamic tunability of the singularity and overcoming the limitations of static structures. This invention breaks through the control limitations of traditional static metasurfaces by changing the Fermi level of the graphene layer 25 covering the opening of the silicon open ring, thereby achieving dynamic tunability of the singularity. The control paradigm shifts from the traditional "structural parameter space" to a "tunable parameter space," allowing the system to be driven along any path in the parameter space without changing the device geometry, thus achieving active search, dynamic locking, and closed-loop control of non-Hermitian singularities. This tunable mechanism also provides tolerance for structural processing errors—performance deviations caused by dimensional deviations can be compensated and optimized by appropriately adjusting the graphene Fermi level.

[0034] Furthermore, the absorption coefficient of liquid water in the near-infrared band is approximately 10 cm⁻¹. -1 The absorption coefficient of water increases sharply by 1-2 orders of magnitude in the terahertz band. The tunable dielectric metasurface with near-infrared non-Hermitian singularities provided in this embodiment can extend the working band of non-Hermitian singularities to the near-infrared band, giving it significant advantages in the detection of water-containing samples: on the one hand, near-infrared light can penetrate water-containing biological tissues, making it suitable for deep in vivo imaging; on the other hand, near-infrared technology does not require complex drying pretreatment and is compatible with high-throughput screening in liquid environments, greatly reducing the complexity and operating cost of the detection system. Therefore, the tunable dielectric metasurface with near-infrared non-Hermitian singularities provided in this embodiment offers a feasible technical solution for practical applications in fields such as chiral molecule detection and biochemical sensing.

[0035] The tunable dielectric metasurface of the near-infrared non-Hermitian singularity in this embodiment is based on coupled-mode theory and equivalent "virtual gain" to construct a PT-symmetric system. Tunable non-Hermitian singularities are achieved by controlling the incident wavelength and the parameter space of the graphene Fermi level.

[0036] In one implementation, according to coupled-mode theory, the dual optical cavity coupling established in the optical system can be expressed as:

[0037] The system's equivalent Hamiltonian operator:

[0038] The equivalent "virtual gain" method verifies that the system can still satisfy the PT symmetry conditions required to realize non-Hermitian singularities even without gain. The non-Hermitian Hamiltonian can be written as:

[0039] in , , It is a PT-symmetric Hamiltonian. To avoid affecting the system attenuation during phase transition.

[0040] Considering both the ease of inter-ring adjustment and the need to satisfy the degeneracy characteristics of the silicon dielectric open-circuit resonator 21 and the germanium dielectric open-circuit resonator 22, the structural parameters were determined as follows: With the center of the sub-unit as the origin (x, y) → (0, 0), the center coordinates of the silicon dielectric open-circuit resonator are (-180nm, -60nm), and the center coordinates of the germanium dielectric open-circuit resonator are (181nm, 64nm), that is, The center positions of the silicon dielectric open-circuit resonator and the germanium dielectric open-circuit resonator are 361 nm apart in the x-axis direction and 124 nm apart in the y-axis direction. The thickness t of both the silicon dielectric open-ring resonator 21 and the germanium dielectric open-ring resonator 22 is 110 nm; the outer diameter L1 of the silicon dielectric open-ring resonator 21 is 363 nm, the width L2 of the silicon dielectric open-ring resonator 21 is 111.5 nm, and the width L3 of the first opening 23 is 110 nm; the outer diameter L5 of the germanium dielectric open-ring resonator 22 is 300 nm, the width L6 of the germanium dielectric open-ring resonator 22 is 80 nm, and the width L7 of the second opening 24 is 100 nm; the substrate unit 11 corresponds to a side length Px of 750 nm along the x-axis of the silicon dielectric open-ring resonator 21; the substrate unit 11 corresponds to a side length Py of 750 nm along the y-axis of the germanium dielectric open-ring resonator 22.

[0041] To establish a tunable structure, a graphene layer 25 is disposed on one side of the silicon dielectric open resonant ring 21, covering the first opening 23. By changing the Fermi level of the graphene layer 25 and controlling the tunable range of the Fermi level of the graphene layer 25 to 0.6 eV, a tunable EP is achieved in the (incident wavelength, Fermi level) parameter space.

[0042] Since the silicon dielectric open-circuit resonator 21 and the germanium dielectric open-circuit resonator 22 are resonator rings with two orthogonal directions, the Hamiltonian can be expressed as:

[0043] in

[0044] The transmission matrix can be written as

[0045] The obtained eigenvalues ​​and phase angles are expressed as follows:

[0046]

[0047] Non-Hermitian singularities are special points where eigenvalues ​​and eigenstates are degenerate. The existence of an EP can be determined by examining the eigenvalue spectrum and phase spectrum.

[0048] Figure 4 These are the intrinsic transmittance and amplitude-phase spectra of graphene at different Fermi levels, among which... Figure 4 (ae) represents the intrinsic transmittance of graphene at the non-Fermi level. Figure 4 Figure (fj) shows the amplitude-phase spectrum of graphene at different Fermi levels, and Figure (ko) corresponds to the intrinsic polarization states at different inter-ring distances at 1.1599 μm. Please refer to [link to relevant documentation]. Figure 4 , Figure 4 (ae) illustrates the evolution of two intrinsic magnitudes from anti-crossing behavior to crossing behavior, however Figure 4 (fj) shows a change in the two intrinsic phase angles from crossover behavior to anti-crossover behavior. The two exhibit an "exchange" phenomenon in their crossover and anti-crossover behaviors, which is consistent with the typical behavior of the characteristic mode near the singular point. Therefore, it can be preliminarily determined that there is an EP point on the tunable dielectric metasurface provided in this embodiment.

[0049] Figure 5 It is the Riemann surface of the magnitude and phase of the eigenvalues ​​in the parameter space (λ,Ge(y)), where Figure 5 (a) is the magnitude of the eigenvalue in the parameter space (λ, Ge(y)). Figure 5 (b) is the phase Riemann surface of the eigenvalues ​​in the parameter space (λ, Ge(y)). Please refer to [link to relevant documentation].Figure 5 Based on the intrinsic amplitude and phase Riemann surface, the position of the yellow dot represents EP, which is approximately represented in this parameter space as (λ). EP ,Ge(y) EP (1.1599μm, 0.5eV) → (1.1599μm, 0.5eV), thus confirming the presence of non-Hermitian singularities on the tunable dielectric metasurface provided in this embodiment.

[0050] The following are a series of properties that non-Hermitian singularities can induce in tunable dielectric metasurfaces: (1) Robust topology protection of state transitions and phases When a parameter loop is completed around the singular point (EP) in parameter space, the two eigenstates of the system will exchange and accumulate a geometric phase of π. Only after two complete parameter loops are completed, i.e., a closed loop, can the eigenstates return to their initial state and accumulate a phase of 2π.

[0051] Figure 6 This is a schematic diagram of the evolution of polarization states, where, Figure 6 (a) represents nine wavelength points (λ). EP A schematic diagram illustrating the evolution of the near polarization state on the Poincaré sphere (from an Antarctic perspective); Figure 6 (b) is a schematic diagram showing the evolution of polarization states in a loop surrounding EP. Please refer to [link / reference]. Figure 6 , Figure 6 (b) shows a loop around EP in the parameter space [λ(μm), EF(eV)], with the loop order (1.1585,0) → (1.1595,0) → (1.1599,0) → (1.1605,0) → (1.1615,0) → (1.1615,0.6) → (1.1605,0.6) → (1.1599,0.6) → (1.1595,0.6) → (1.1585,0.6). The evolution of the polarization ellipse in the figure clearly shows that after one revolution around EP, the two intrinsic polarization states are interchanged. The polarization states are tracked... Figure 6 (b) The specific path is Figure 6 (a) Individual points on the route where EF = 0 eV in the fourth quadrant and EF = 0.6 eV in the first quadrant. In this route, Figure 5 (a) The evolution process from solid line to dashed line, from solid to hollow shows the change of polarization state, and it can be seen that a parameter is achieved by surrounding EP, and state 1 will be transformed into state 2; Figure 6(b) The evolution trajectory of the polarization ellipse is clearly shown: after one revolution around the EP, the two intrinsic polarization states interchange. This eigenstate exchange process is accompanied by the accumulation of π phase, which has topological protection properties. By combining the 2π topological phase accumulated in the closed loop around the EP (any closed loop that surrounds but does not pass through the EP) with ordinary geometric phase, it can be further applied to phase manipulation fields such as holographic imaging.

[0052] (2) Strong chirality Throughout the process of tuning the Fermi level of graphene from 0 to 0.6 eV, at λ EP A distinct depression was observed at each location. Figure 7 It is the transmission spectrum of the metasurface, in which, Figure 7 (a) shows the transmission spectra of the metasurface corresponding to different Fermi levels of graphene under linear polarization. Figure 7 (b) shows the transmission spectra of the metasurface corresponding to different Fermi levels of graphene under circular polarization. Figure 7 (c) represents T near EP based on circular polarization. rl Amplitude spectrum Figure 7 (d) represents the T value near EP based on circular polarization. rl Phase spectrum.

[0053] Please see Figure 7 To analyze the data at the depression in more detail, Figure 7 (c) is Figure 7 (b) shows a magnified view of the transmission concave region, which allows for a clearer observation of the incident wavelength λ. EP Graphene Fermi level E F EP At that time, the right-hand circularly polarized transmission coefficient T rl The value is approximately zero, indicating that the channel for converting from a left-handed circularly polarized state (LCP) to a right-handed circularly polarized state (RCP) is completely blocked, and the conversion efficiency from LCP to RCP is 0. This phenomenon is the most direct and typical manifestation of strong chirality or perfect chirality, indicating that the tunable dielectric metasurface of the near-infrared non-Hermitian singularity provided in this embodiment has absolute, unidirectional non-reciprocity in response to the two circularly polarized states.

[0054] (3) Phase change Figure 7 (d) shows that when E F When the transmittance increases from 0.46 eV to 0.5 eV, the phase of the transmittance coefficient is at λ. EP A sudden change occurs at this point, and this characteristic can be applied to the field of high-sensitivity sensing.

[0055] Example 2 This embodiment provides the application of the tunable dielectric metasurface of near-infrared non-Hermitian singularity in the field of sensing.

[0056] In Example 1, the tunable dielectric metasurface of the near-infrared non-Hermitian singularity is surrounded by air. When the refractive index of the environment changes, the position of the non-Hermitian singularity in parameter space will shift. At a fixed incident wavelength, this shift is manifested in the transmission coefficient T. rl Abrupt changes in amplitude and transmission phase. Based on the high sensitivity of non-Hermitian singularities to perturbations, this embodiment proposes an application for concentration detection.

[0057] The change in the concentration C of the analyte causes a change in the local equivalent refractive index n of the metasurface. This refractive index change is the effective Hamiltonian of the perturbation term Δn entering the system. Near the non-Hermitian singularity, the system's response to the perturbation is amplified to an extreme degree, specifically manifested as the following three observable changes: (1) Wavelength shift at the non-Hermitian singularity: the incident wavelength λ corresponding to the non-Hermitian singularity. EP (2) Change in transmission amplitude: T rl (3) The indentation at the singular point; T rl A sudden change in phase occurs.

[0058] By pre-calibrating the quantitative relationship between the above-mentioned observable changes and the concentration of the analyte (e.g., Δλ), EP ~C), the tunable dielectric metasurface is immersed in the analyte, and the change in the observable quantity mentioned above is detected. The concentration C of the analyte can then be deduced from the measured change in the physical quantity.

[0059] When metasurfaces are applied to biochemical sensing, changes in the concentration of the analyte will cause it to form adsorption layers with different equivalent refractive indices on the tunable dielectric metasurface, thus perturbing the near-field optical environment of the device. This perturbation is significantly amplified near non-Hermitian singularities, ultimately manifesting as wavelength shifts or amplitude changes in singularity features (such as chiral depressions and phase abrupt changes) in the transmission spectrum. By calibrating the functional relationship between this shift or change and the concentration, highly sensitive and quantitative detection of the analyte can be achieved.

[0060] This embodiment proposes to combine the physical properties of tunable dielectric metasurfaces at near-infrared non-Hermitian singularities with the application requirements of the near-infrared band. By establishing the relationship between the changes in physical quantities at the singularity and the parameters of the analyte, the basic physical effects of non-Hermitian singularities are applied to practical detection applications. The working band of non-Hermitian singularities is extended to the near-infrared, and active and reversible control over their position and state is achieved.

[0061] This invention is not limited to the above-described embodiments. If any modifications or variations to this invention do not depart from the spirit and scope of this invention, and if such modifications and variations fall within the scope of the claims and equivalent technologies of this invention, then this invention also intends to include such modifications and variations.

Claims

1. A tunable dielectric metasurface with near-infrared non-Hermitian singularities, characterized in that: Includes a silicon dioxide substrate and several non-Hermitian singularity units; The silicon dioxide substrate includes a plurality of substrate units; A number of the aforementioned non-Hermitian singularity units are periodically arranged on the silicon dioxide substrate; Each of the aforementioned non-Hermitian singularity units includes a silicon dielectric open-circuit resonator and a germanium dielectric open-circuit resonator disposed on a single substrate unit; The silicon dielectric open-ended resonant ring and the germanium dielectric open-ended resonant ring are located in the same plane; The silicon dielectric open-ended resonant ring and the germanium dielectric open-ended resonant ring are arranged perpendicularly to each other. The silicon dielectric open-loop resonator is arranged along the x-axis direction, and the silicon dielectric open-loop resonator has a first opening along the x-axis direction, the length of the first opening being not less than the width of the silicon dielectric open-loop resonator. The first opening is positioned away from the germanium dielectric open resonant ring. A graphene layer is disposed on one side of the silicon dielectric open resonant ring, and the graphene layer covers the first opening. The germanium dielectric open-ended resonant ring is arranged along the y-axis and is located to the right of the silicon dielectric open-ended resonant ring; The silicon dielectric open resonant ring is provided with a second opening along the y-axis direction, and the length of the second opening is not less than the width of the silicon dielectric resonant ring. The opening directions of the first opening and the second opening are orthogonal; The resonant wavelengths of the silicon dielectric open-ended resonant ring and the germanium dielectric open-ended resonant ring are close to the degenerate region.

2. The tunable dielectric metasurface with near-infrared non-Hermitian singularities according to claim 1, characterized in that: The thickness t of both the silicon dielectric resonant ring and the germanium dielectric resonant ring is 110 nm; the center positions of the silicon dielectric resonant ring and the germanium dielectric resonant ring are 361 nm apart in the x-axis direction and 124 nm apart in the y-axis direction. The outer diameter L1 of the silicon dielectric resonant ring is 363 nm, the width L2 of the silicon dielectric resonant ring is 111.5 nm, and the width L3 of the first opening is 110 nm. The outer diameter L5 of the germanium dielectric resonant ring is 300 nm, the width L6 of the germanium dielectric resonant ring is 80 nm, and the width L7 of the second opening is 100 nm.

3. The tunable dielectric metasurface with near-infrared non-Hermitian singularities according to claim 1, characterized in that: The non-Hermitian singularity unit is embedded in the base unit.

4. The tunable dielectric metasurface with near-infrared non-Hermitian singularities according to any one of claims 1-3, characterized in that: The substrate unit corresponds to a side length Px of 750 nm along the x-axis of the silicon dielectric resonant ring; The substrate unit corresponds to a germanium dielectric resonant ring with a side length Py of 750 nm along the y-axis.

5. The tunable dielectric metasurface with near-infrared non-Hermitian singularities according to claim 1, characterized in that: The Fermi level of the graphene layer is tunable in the range of 0 to 0.6 eV.

6. The application of the tunable dielectric metasurface with near-infrared non-Hermitian singularities as described in any one of claims 1-5 in the field of sensing.

7. The application of the tunable dielectric metasurface according to claim 6 in the field of sensing, characterized in that, Includes the following steps: Quantitative relationship between the observable change at pre-calibrated non-Hermitian singularities and the concentration of the analyte; Immerse a tunable dielectric metasurface into the test object to detect observable changes; Based on the quantitative relationship, the concentration C of the analyte is obtained.

Images