A non-hermitian metasurface and a method for constructing the same
By combining composite and complementary layer structures with dielectric layers and hollow cylinders, the conductivity of vanadium dioxide is adjusted to construct a non-Hermitian metasurface. This solves the problem of insufficient control flexibility in existing technologies, realizes singularity characteristics at multiple frequency points, broadens the application range, and is suitable for fields such as optical devices and sensors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV OF TECH
- Filing Date
- 2023-06-25
- Publication Date
- 2026-06-26
AI Technical Summary
Existing strategies for constructing non-Hermitian metasurfaces are limited by passive structural design, making it difficult to achieve flexible control and multifunctionality, especially for single singularity applications at fixed frequencies, and it is difficult to realize singularity characteristics at multiple frequency points.
By employing a composite and complementary layer structure, combined with a dielectric layer, and hollow cylinders are hollowed out, and by adjusting the conductivity of vanadium dioxide to produce singularities at different frequencies, tunability is achieved using phase change materials, thus constructing a non-Hermitian metasurface.
It enables flexible control of non-Hermitian metasurfaces, broadens the application range, and can realize chiral EP effect and unidirectional non-reflection phenomenon at two frequency points, making it suitable for optical devices, sensors and antenna design and other fields.
Smart Images
Figure CN116565572B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electromagnetic wave manipulation technology, and more specifically relates to a non-Hermitian metasurface and its construction method. Background Technology
[0002] Metasurfaces are artificially layered materials with a thickness less than the wavelength. Because metasurfaces can be artificially modified in terms of material, shape, and size, clever structural parameter design can enable metasurfaces to exhibit special properties not found in their intrinsic materials, such as negative refractive index and negative permittivity. Materials with these properties do not exist in nature. Therefore, metasurface research has greatly broadened the research content and scope in fields such as electromagnetics, optics, and materials science, and has a wider range of application prospects.
[0003] In recent years, researchers have been studying non-Hermitian optical systems on metasurface platforms. The combination of non-Hermitian singularity effects has further enriched the research content and application scenarios in the metasurface field. Compared with traditional Hermitian systems, non-Hermitian systems break parity-time (PT) symmetry and possess a special point—the singularity (EP point). At the non-Hermitian singularity, the system's eigenvalues and eigenstates are reduced from two or more to one, accompanied by many interesting phenomena, such as unidirectional non-reflection, coherent perfect absorption, enhanced sensing, and topological changes. The unique effects at the singularity make it of significant research value and application prospects in many optical fields.
[0004] Currently, research on metasurfaces is largely limited to exploring their electromagnetic control functions under fixed structural designs. Although the designed metasurfaces can achieve non-Hermitian transitions and possess corresponding singularity properties, the passive structural design restricts the realization, tuning, and application flexibility of non-Hermitian metasurfaces. With further research, existing technologies introduce phase change materials into passive metasurface structures to achieve tunability and multifunctionality. However, most studies are limited to single singularities at fixed frequencies, or require changing different conditions to achieve double singularities, thus limiting the controllability and application range of non-Hermitian metasurfaces.
[0005] This shows that existing strategies for constructing non-Hermitian metasurfaces still need to be optimized. Summary of the Invention
[0006] Based on the aforementioned shortcomings and deficiencies in the prior art, one of the objectives of this invention is to at least solve one or more of the aforementioned problems in the prior art. In other words, one of the objectives of this invention is to provide a non-Hermitian metasurface and a method for constructing it that meets one or more of the aforementioned requirements.
[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:
[0008] In a first aspect, the present invention provides a non-Hermitian metasurface, comprising a composite layer and a complementary layer coupled to the composite layer, wherein a dielectric layer is disposed between the composite layer and the complementary layer; the composite layer is perforated with a plurality of hollow cylinders; the complementary layer and the positions corresponding to the solid portions of the plurality of hollow cylinders are all perforated.
[0009] Through the above technical solution, the composite layer is made of a mixture of different materials. By adjusting the structural parameters and selecting the types of materials, the composite layer and the complementary layer are coupled, thereby realizing the device's influence on the reflection of incident electromagnetic waves in the microwave band. Furthermore, by changing the conductivity of vanadium dioxide, a material used in the composite layer, singularities appear at two different frequency points on the non-Hermitian metasurface, achieving the control of the non-Hermitian metasurface. This effectively broadens the application range of non-Hermitian metasurfaces and is more conducive to their functionalization and device integration. This non-Hermitian metasurface has a simple structure, consisting of only three layers from top to bottom: the composite layer, the dielectric layer, and the complementary layer. The structure is distinct and clearly defined, and its realization only requires adjusting the dimensions and materials of the composite layer, the dielectric layer, and the complementary layer.
[0010] In a preferred embodiment of the present invention, the hollow cylinder comprises an aluminum segment and a vanadium dioxide segment; the central angle of the aluminum segment corresponding to the hollow cylinder ranges from [180°, 220°], and the central angle of the vanadium dioxide segment corresponding to the hollow cylinder ranges from [140°, 180°]; the ratio of the aluminum segment to the vanadium dioxide segment is 29:7.
[0011] Through the above technical solution, the composite layer is made of aluminum and vanadium dioxide. In the construction of non-Hermitian supersurface, phase change materials are introduced to achieve tunability. Phase change materials are a class of materials that can undergo physical or chemical phase changes under temperature, pressure or other external stimuli. Phase change materials can change atomic arrangement, microstructure and stress state during the phase change process to achieve tunable electromagnetic response characteristics.
[0012] As a preferred embodiment of the present invention, the conductivity of the vanadium dioxide segment is adjustable within the range of [200s / m, 250000s / m].
[0013] Through the above technical solution, vanadium dioxide, a semiconductor material, exhibits electrical properties closely related to temperature. At low temperatures, vanadium dioxide possesses low resistivity, but this resistivity increases rapidly with rising temperature. When the temperature rises and exceeds a threshold temperature, vanadium dioxide undergoes a phase transition from an insulating state to a metallic state. By adjusting the conductivity of the vanadium dioxide segment, the transition from an insulating to a metallic state can be achieved, enabling the system to transition from a Hermitian state to a non-Hermitian state, thus constructing a non-Hermitian metasurface. This non-Hermitian metasurface can simultaneously achieve chiral EP effect and unidirectional non-reflection at two frequency points. These characteristics provide broader possibilities for the application of metasurfaces, including optical devices, sensors, and antenna design.
[0014] As a preferred embodiment of the present invention, the inner radius of the hollow cylinder is set in the range of [3.5nm, 4.5nm]; the outer radius of the hollow cylinder is set in the range of [5.6nm, 6.5nm].
[0015] In a preferred embodiment of the present invention, the thickness of the composite layer and the complementary layer are equal; the thickness of the composite layer and the complementary layer is set within the range of [250nm, 350nm].
[0016] In a preferred embodiment of the present invention, the hollow cylinders are arranged periodically.
[0017] In a preferred embodiment of the present invention, the complementary layer is made of aluminum; and the dielectric layer is made of sapphire.
[0018] Secondly, the present invention provides a method for constructing a non-Hermitian metasurface, based on a non-Hermitian metasurface from any of the above-mentioned schemes, comprising the steps of:
[0019] S1. Construct a composite layer, a dielectric layer, and a complementary layer that are connected sequentially from top to bottom;
[0020] S2. Several hollow cylinders are cut out on the composite layer;
[0021] S3. Hollowing out the complementary layer at the positions corresponding to the solid portions of the plurality of hollow cylinders.
[0022] S4. Adjust the electrical conductivity of vanadium dioxide in the composite layer so that vanadium dioxide changes from an insulating state to a metallic state, in order to construct a dual-band non-Hermitian metasurface.
[0023] The above technical solution simplifies the construction process of the non-Hermitian metasurface, requiring only the setting of the dimensions and materials of the composite layer, the dielectric layer, and the complementary layer. By adjusting the conductivity of vanadium dioxide in the composite layer, the vanadium dioxide is transformed from an insulating state to a metallic state, enabling the system to transition from a Hermitian state to a non-Hermitian state, thus completing the construction of the non-Hermitian metasurface. This non-Hermitian metasurface can simultaneously achieve chiral EP effect and unidirectional non-reflection at two frequency points. These characteristics provide broader possibilities for the application fields of metasurfaces, including optical devices, sensors, and antenna design.
[0024] As a preferred embodiment of the present invention, the conductivity of vanadium dioxide is adjusted by adjusting the temperature of vanadium dioxide; the temperature adjustment range of vanadium dioxide is [60℃, 70℃].
[0025] As a preferred embodiment of the present invention, the temperature of vanadium dioxide is adjusted by heating or laser.
[0026] Compared with the prior art, the present invention has the following beneficial effects:
[0027] Firstly, by adjusting structural parameters and selecting material types, the composite layer and the complementary layer are coupled, thereby enabling the device to influence the reflection of incident electromagnetic waves in the microwave band. Furthermore, by changing the conductivity of vanadium dioxide, a material used in the composite layer, singularities appear at two different frequency points on the non-Hermitian metasurface, realizing the control of the non-Hermitian metasurface. This effectively broadens the application range of non-Hermitian metasurfaces and is more conducive to realizing the functionalization and device integration of non-Hermitian metasurfaces.
[0028] Secondly, the construction process of the non-Hermitian metasurface is simple, requiring only the setting of the size and material of the composite layer, the dielectric layer, and the complementary layer. By adjusting the conductivity of vanadium dioxide in the composite layer, vanadium dioxide can be transformed from an insulating state to a metallic state, enabling the system to transform from a Hermitian state to a non-Hermitian state, thus completing the construction of the non-Hermitian metasurface. The non-Hermitian metasurface can simultaneously achieve chiral EP effect and unidirectional non-reflection at two frequency points. These characteristics provide broader possibilities for the application fields of metasurfaces, including optical devices, sensors, and antenna design.
[0029] Further or more detailed beneficial effects will be described in conjunction with specific embodiments in the detailed implementation. Attached Figure Description
[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0031] Figure 1 This is a schematic diagram of the structure of a non-Hermitian metasurface described in this invention.
[0032] Figure 2 This is a schematic diagram of the unit structure of a non-Hermitian metasurface described in this invention.
[0033] Figure 3 This is a top view of a non-Hermitian metasurface described in this invention.
[0034] Figure 4 This is a side view of a non-Hermitian metasurface described in this invention.
[0035] Figure 5 This is a graph showing the relationship between the reflectivity of a non-Hermitian metasurface described in this invention when vanadium dioxide is in a metallic state (i.e., with a conductivity of 200,000 S / m) and incident from the front and back sides.
[0036] Figure 6 This is a graph showing the relationship between the reflectivity of a non-Hermitian metasurface described in this invention when vanadium dioxide is in an insulating state (i.e., the conductivity is 200 S / m) and the reflectivity is incident from the front and back sides.
[0037] Figure 7 This is a graph showing the relationship between the reflectivity of a non-Hermitian metasurface described in this invention and the electrical conductivity of vanadium dioxide at a frequency of 2.522 GHz, when incident from the front and back sides.
[0038] Figure 8 This is a graph showing the relationship between the reflectivity of a non-Hermitian metasurface described in this invention and the electrical conductivity of vanadium dioxide at a frequency of 5.498 GHz, when the reflectivity is measured by both front and back incident light.
[0039] Figure 9 This is a graph showing the relationship between the real and imaginary eigenvalues of a non-Hermitian metasurface described in this invention and the conductivity of vanadium dioxide at a frequency of 2.522 GHz.
[0040] Figure 10 This is a graph showing the relationship between the real and imaginary eigenvalues of a non-Hermitian metasurface as described in this invention at a frequency of 5.498 GHz and the conductivity of vanadium dioxide.
[0041] Figure 11This is a diagram showing the eigenstate switching relationship of a non-Hermitian metasurface as described in this invention when it surrounds the first EP point.
[0042] Figure 12 This is a diagram showing the relationship between the eigenstate switching of a non-Hermitian metasurface as described in this invention when it surrounds the second EP point.
[0043] Figure 13 This is a flowchart of a method for constructing a non-Hermitian metasurface as described in this invention.
[0044] Icon labels:
[0045] 1. Vanadium dioxide segment; 2. Aluminum segment; 3. Dielectric layer; 4. Hollowed-out area of complementary layer; 5. Complementary layer. Detailed Implementation
[0046] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.
[0047] In the following description, several embodiments of this application are provided. Different embodiments can be substituted or combined. Therefore, this application can also be considered to include all possible combinations of the same and / or different embodiments described. Thus, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then this application should also be considered to include embodiments containing one or more other possible combinations of A, B, C, and D, even if such embodiments are not explicitly described in the following text.
[0048] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the described elements without departing from the scope of this application. Various processes or components may be appropriately omitted, substituted, or added to the examples. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.
[0049] To facilitate a better understanding of the embodiments of this application, the application scenarios will be explained before providing a detailed explanation of the specific implementation methods.
[0050] Example 1:
[0051] like Figure 1-4As shown, this embodiment provides a non-Hermitian metasurface, including a composite layer and a complementary layer coupled to the composite layer, wherein the complementary layer is made of aluminum. The composite layer and the complementary layer have the same thickness, and the thickness h of the composite layer and the complementary layer is set in the range of [250nm, 350nm], preferably 250nm, 260nm, 270nm, 280nm, 290nm, 300nm, 310nm, 320nm, 330nm, 340nm, and 350nm.
[0052] The composite layer is perforated with several hollow cylinders, such as... Figure 4 The hollow cylinders are arranged periodically, where p represents the period of the hollow cylinders along the X or Y direction in the XY plane. The inner radius r2 of the hollow cylinders is set in the range of [3.5nm, 4.5nm], preferably 3.5nm, 3.6nm, 3.7nm, 3.8nm, 3.9nm, 4nm, 4.1nm, 4.2nm, 4.3nm, 4.4nm, 4.5nm. The outer radius r1 of the hollow cylinders is set in the range of [5.6nm, 6.5nm], preferably 5.6nm, 5.7nm, 5.8nm, 5.9nm, 6nm, 6.1nm, 6.2nm, 6.3nm, 6.4nm, 6.5nm.
[0053] The hollow cylinder comprises aluminum segments and vanadium dioxide segments. The central angle of the aluminum segments corresponding to the hollow cylinder ranges from [180°, 220°], and the central angle θ of the vanadium dioxide segments corresponding to the hollow cylinder ranges from [140°, 180°]. The ratio of the aluminum segments to the vanadium dioxide segments is 29:7. The composite layer is made of aluminum and vanadium dioxide, wherein the dielectric constant of vanadium dioxide is 10. Introducing phase change materials to achieve tunability in the construction of non-Hermitian metasurfaces is a technique. Phase change materials are materials capable of undergoing physical or chemical phase transitions under temperature, pressure, or other external stimuli. During phase transitions, phase change materials can alter atomic arrangement, microstructure, and stress state, thereby achieving tunable electromagnetic response characteristics.
[0054] The conductivity of the vanadium dioxide segment is adjustable within the range of [200 S / m, 250,000 S / m]. The composite layer is made of aluminum and vanadium dioxide. Phase change materials are introduced into the construction of the non-Hermitian metasurface to achieve tunability. Phase change materials are materials that can undergo physical or chemical phase changes under temperature, pressure, or other external stimuli. During the phase change process, phase change materials can alter atomic arrangement, microstructure, and stress state, thereby achieving tunable electromagnetic response characteristics. For example... Figure 5-8 As shown, the non-Hermitian metasurface can be controlled by changing the conductivity of the vanadium dioxide segment. Figure 5As shown, vanadium dioxide is in a metallic state, and a unidirectional non-reflection phenomenon can be clearly observed at two frequency points, namely 2.522 GHz and 5.498 GHz, such as... Figure 6 As shown, vanadium dioxide is in an insulating state, and no special phenomenon occurs during reflection. Through... Figure 5 and Figure 6 The comparison shows that this embodiment, by adjusting the conductivity of the vanadium dioxide segment, enables the active control of the non-Hermitian metasurface by allowing vanadium dioxide to transition from an insulating state to a metallic state. The effect of vanadium dioxide conductivity on the reflectivity of incident electromagnetic waves differs depending on the frequency. For example... Figure 7 As shown, at 2.522 GHz, as the conductivity of vanadium dioxide increases, the front reflectivity of the implemented scheme decreases rapidly during the transition from the insulating state to the metallic state, while the back reflectivity remains greater than 0.5. For example... Figure 8 As shown, at 5.498 GHz, with the increase of vanadium dioxide conductivity, the reflectivity of the reverse side of the implemented scheme decreases rapidly during the transition from the insulating state to the metallic state, while the reflectivity of the front side remains relatively stable, hovering around 0.6. Under EP conditions, when the vanadium dioxide conductivity is 200,000 S / m, the reflections of the front and reverse sides at both frequency points exhibit chiral response characteristics, indicating that a chiral non-Hermitian metasurface has been achieved in this embodiment.
[0055] The complementary layer is hollowed out at the positions corresponding to the solid parts of the hollow cylinders.
[0056] A dielectric layer is disposed between the composite layer and the complementary layer. The dielectric layer is made of sapphire material with a dielectric constant of 9.4. The thickness H of the dielectric layer is set in the range of [2mm, 2.5mm], preferably 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, or 2.5mm.
[0057] This non-Hermitian metasurface has a simple structure consisting of only three layers from top to bottom: the composite layer, the dielectric layer, and the complementary layer. The structure is distinct and clearly defined, and its realization only requires adjusting the size and material of the composite layer, the dielectric layer, and the complementary layer.
[0058] The composite layer is made of a mixture of different materials. By adjusting the structural parameters and selecting the types of materials, the composite layer is coupled with the complementary layer, thereby realizing the device's influence on the reflection of incident electromagnetic waves in the microwave band. By changing the conductivity of vanadium dioxide, a material used in the composite layer, singularities appear at two different frequency points on the non-Hermitian metasurface, realizing the control of the non-Hermitian metasurface, effectively broadening the application range of non-Hermitian metasurfaces, and making it more conducive to the functionalization and device integration of non-Hermitian metasurfaces.
[0059] To further demonstrate that this embodiment is a non-Hermitian metasurface, evolution simulations were performed on the eigenvalues of this embodiment. The theoretical basis for verification is that at non-Hermitian singularities, the system's eigenvalues and eigenstates are reduced from two or more to one. In exploring the intrinsic principles of non-Hermitian metasurfaces, the Hamiltonian from physics is introduced into the optical system, allowing the Hamiltonian to be equivalently represented using the scattering matrix. Typically, the scattering matrix of a dual-channel optical system can be expressed as:
[0060]
[0061] Where t represents the transmission coefficient of electromagnetic waves, represents the forward reflection coefficient of electromagnetic waves, and represents the backward reflection coefficient of electromagnetic waves.
[0062] Therefore, the eigenvalues corresponding to the scattering matrix of the system can be obtained as follows:
[0063]
[0064] The eigenstate is:
[0065]
[0066] If and only at that time When λ1 = λ2, the eigenvalues and eigenstates of the system become degenerate. This also means that the system changes from a Hermitian system to a non-Hermitian system, and the EP point appears.
[0067] like Figure 9 As shown, at 2.522 GHz, the real and imaginary parts of the eigenvalues in this embodiment exhibit a splitting and merging evolution process with the change in the conductivity of vanadium dioxide. When the conductivity of vanadium dioxide is 200,000 S / m, both the real and imaginary parts of the eigenvalues degenerate simultaneously, proving the occurrence of the EP point. Figure 10 As shown, at 5.498 GHz, the real and imaginary parts of the eigenvalues in this embodiment exhibit a splitting and merging evolution process with changes in the conductivity of vanadium dioxide. When the conductivity of vanadium dioxide is 200,000 S / m, both the real and imaginary parts of the eigenvalues degenerate simultaneously, proving the appearance of the EP point. Its chiral response characteristics are also reflected in the switching process of the eigenstates during dynamic orbit around the EP. For example... Figure 11 and Figure 12 As shown, the eigenstate switching around the EP point dynamically in parameter space at 2.522 GHz and 5.498 GHz is illustrated. Taking clockwise rotation as an example, at 2.522 GHz, the eigenstate transitions from a "circular" state to a "star" state and back to a "circular" state; while at 5.498 GHz, the eigenstate transitions from a "star" state to a "circular" state and back to a "star" state. The eigenstate switching around the two EP points exhibits a chiral relationship, further demonstrating that this embodiment is a non-Hermitian metasurface with chiral response characteristics.
[0068] Example 2:
[0069] like Figure 13 As shown, this embodiment provides a method for constructing a non-Hermitian metasurface, based on a non-Hermitian metasurface from any of the above schemes, including the following steps:
[0070] S1. Construct a composite layer, a dielectric layer, and a complementary layer that are connected sequentially from top to bottom;
[0071] S2. Several hollow cylinders are cut out on the composite layer;
[0072] S3. Hollowing out the complementary layer at the positions corresponding to the solid portions of the hollow cylinders;
[0073] S4. Adjust the electrical conductivity of vanadium dioxide in the composite layer so that vanadium dioxide changes from an insulating state to a metallic state, in order to construct a dual-band non-Hermitian metasurface.
[0074] Specifically, this embodiment provides a preferred implementation method in step S2, in which the conductivity of vanadium dioxide is adjusted by adjusting the temperature of vanadium dioxide, and the temperature adjustment range of vanadium dioxide is [60℃, 70℃].
[0075] Specifically, this embodiment provides a preferred implementation method, which uses heating or laser to adjust the temperature of vanadium dioxide.
[0076] The construction process of the non-Hermitian metasurface is simple, requiring only the setting of the dimensions and materials of the composite layer, the dielectric layer, and the complementary layer. By adjusting the conductivity of vanadium dioxide in the composite layer, the vanadium dioxide is transformed from an insulating state to a metallic state, enabling the system to transition from a Hermitian state to a non-Hermitian state, thus completing the construction of the non-Hermitian metasurface. The non-Hermitian metasurface can simultaneously achieve chiral EP effect and unidirectional non-reflection at two frequency points. These characteristics provide broader possibilities for the application fields of metasurfaces, including optical devices, sensors, and antenna design.
[0077] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.
[0078] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.
[0079] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of embodiments of this disclosure upon considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.
Claims
1. A non-Hermitian metasurface, characterized in that: It includes a composite layer and a complementary layer coupled to the composite layer, wherein a dielectric layer is disposed between the composite layer and the complementary layer; The composite layer is perforated with several hollow cylinders; The complementary layer is hollowed out at the positions corresponding to the solid parts of the plurality of hollow cylinders. The complementary layer is made of aluminum, and the composite layer has the same thickness as the complementary layer. The thickness of the composite layer and the complementary layer is set within the range of [250nm, 350nm]. The hollow cylinders are arranged periodically, and the inner radius of the hollow cylinders is set in the range of [3.5nm, 4.5nm], and the outer radius of the hollow cylinders is set in the range of [5.6nm, 6.5nm]. The composite layer is made of aluminum and vanadium dioxide. The hollow cylinder comprises an aluminum segment and a vanadium dioxide segment, wherein the ratio of the aluminum segment to the vanadium dioxide segment is 29:7, and the conductivity of the vanadium dioxide segment is adjustable within the range of [200s / m, 250000s / m]. The dielectric layer is made of sapphire material, and the thickness of the dielectric layer is set in the range of [2mm, 2.5mm]. By adjusting the electrical conductivity of vanadium dioxide in the composite layer, singularities appeared on the non-Hermitian metasurface at two different frequency points.
2. A method for constructing a non-Hermitian metasurface, based on the non-Hermitian metasurface described in claim 1, characterized in that, Including the following steps: S1. Construct a composite layer, a dielectric layer, and a complementary layer that are connected sequentially from top to bottom; S2. Several hollow cylinders are cut out on the composite layer; S3. Hollowing out the complementary layer at the positions corresponding to the solid portions of the hollow cylinders; S4. Adjust the electrical conductivity of vanadium dioxide in the composite layer so that vanadium dioxide changes from an insulating state to a metallic state, in order to construct a dual-band non-Hermitian metasurface.
3. The method for constructing a non-Hermitian metasurface according to claim 2, characterized in that, In step S2: The conductivity of vanadium dioxide can be adjusted by regulating its temperature. The temperature range for vanadium dioxide is [60℃, 70℃].
4. The method for constructing a non-Hermitian metasurface according to claim 3, characterized in that: The temperature of vanadium dioxide can be adjusted by heating or laser.