Chiral metasurface design based on dirac dynamic tunable materials

Abstract

The application discloses a chiral metasurface design based on Dirac dynamic adjustable material, and the upper layer of the metasurface is composed of silver and an electric phase change material Dirac, the middle medium layer is BCB, and the substrate material is silver. The circular dichroism chiral metasurface realizes the regulation of transmittance and reflectance in the 5.5~6.0 THz wave band, thereby regulating the circular dichroism of reflection. The maximum of the reflected circular dichroism can reach 0.91, the minimum of the circular dichroism can be close to-0.91, and the circular dichroism is 0 in the closed state. The regulation in three modes is realized. The structure is a multi-mode circular dichroism chiral metasurface based on adjustable material, and can be applied to holographic imaging, vortex generation, beam splitting and the like. The application realizes the dynamic regulation of three circular dichroism states by changing the electric conductivity of the electric phase change material Dirac, independently controlling the Fermi energy level of the double-side BDS to break the spatial mirror symmetry, and causing the surface electromagnetic field to be strongly asymmetric localized coupling, thereby realizing the dynamic regulation of three circular dichroism states.

Description

Technical Field

[0001] This invention relates to the field of micro-nano integrated optoelectronics technology, specifically to a Dirac-based switchable chiral metasurface. Background Technology

[0002] Metamaterials, as a novel material that has gradually developed in the 21st century, have received extensive research and attention in the field of stealth materials due to their unique properties and excellent tunability, and have become a key direction in stealth research. They are a new type of material that does not exist in nature, is artificially designed, and possesses a periodic structure. Metamaterials possess special properties not found in natural materials, such as negative magnetic permeability and dielectric constant, and anomalous Doppler effect.

[0003] Chiral metasurfaces are an innovative technology that employs special designs and materials to produce different responses to different circularly polarized waves. Highly efficient chiral metasurfaces can strongly absorb one type of circularly polarized wave while transmitting (reflecting) the opposite wave, achieving independent modulation of LCP or RCP waves, thereby producing phenomena such as circular dichroism and asymmetric transmission.

[0004] In 2006, Fedotov et al. discovered polarization-selective asymmetric propagation of CPL in planar chiral "fish-scale" metasurfaces, originating from spatial symmetry breaking. Driven by application needs, researchers have proposed various barrier-breaking structures to achieve asymmetric propagation, continuously improving efficiency. The polarization selectivity of forward-incident light differs from that of backward-incident light. This effect can be used as optical isolators, polarization converters, chiral absorbers, etc. However, previous studies have mainly focused on polarization selectivity in a single transmission or reflection mode. Recently, in the near-infrared and terahertz regions, some metasurfaces have exhibited circular polarization selectivity in both transmission and reflection. Summary of the Invention

[0005] The purpose of this invention is to provide a chiral metasurface design based on Dirac dynamically tunable materials, which can achieve switching of circular dichroism in electromagnetic response at different frequencies.

[0006] To achieve the above objectives, this invention provides a chiral metasurface design based on Dirac dynamically tunable materials, which is realized through the following technical solution:

[0007] A chiral metasurface design based on Dirac dynamically tunable material is proposed, which utilizes the electrical phase transition properties of Dirac and the electromagnetic response of the metasurface at different frequencies to switch the already arranged phase distribution, while simultaneously switching the circular dichroism.

[0008] The above technical solution can be preferably adopted in the following ways:

[0009] The structure described above. Figure 1As shown in (a), the cell structure consists of three layers, from bottom to top: a silver substrate, BCB, and a top layer composed of a metal rectangular split ring consisting of Dirac and Ag.

[0010] Compared with other technologies, the present invention has the following advantages:

[0011] It exhibits circular dichroism. Due to the symmetrical broken structure of this invention, it produces different responses to different circularly polarized waves, thereby generating phenomena such as circular dichroism and asymmetric transmission.

[0012] This structure is based on a multimodal circular dichroic chiral metasurface made of tunable material. It switches the pre-arranged phase distribution and the circular dichroism by changing the electromagnetic response at different frequencies, and can be applied to multiple fields.

[0013] This structure, based on a multimodal circular dichromatic chiral metasurface made of tunable materials, can be applied to holographic imaging, vortex beam generation, beam splitting, and other applications. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a chiral metasurface design structure based on Dirac dynamically tunable materials.

[0015] Figure 2 This is the circular dichroism spectrum curve for Mode I.

[0016] Figure 3 This is the circular dichroism spectrum curve for Mode II.

[0017] Figure 4 This is the circular dichroism spectrum of Mode III.

[0018] Figure 5 The graphs show the circular dichroism spectra of the three modes. Detailed Implementation

[0019] To better understand the present invention, the following description and explanation are provided in conjunction with the embodiments and accompanying drawings. The embodiments described below are for illustrative purposes only and are not intended to limit the present invention.

[0020] like Figure 1 As shown in (a), a chiral metasurface design based on Dirac dynamically tunable material is presented. The unit cell consists of a three-layer structure, from bottom to top: a silver substrate, BCB, and a top layer composed of a metal rectangular split ring made of Dirac and Ag.

[0021] like Figure 1As shown in (b), the bottom layer is a silver substrate with a fixed thickness of 0.6 µm. The middle layer is a BCB dielectric material with a fixed thickness of 9 µm. The top rectangular layer is made of silver material with a fixed thickness of 0.25 µm, and the bottom of the rectangle is made of Dirac material with a fixed thickness of 0.25 µm. Other materials include P... x and P y L1 is fixed at 28µm, L2 at 40µm, L3 at 44µm, and L3 at 7.8µm. W1, W2, and W3 are fixed at 2µm, 6.6µm, and 1.2µm, respectively.

[0022] like Figure 2 As shown, in the 5.5~6.0THz band, the response of circularly polarized light is shown when the left Dirac is in a metallic state and the right Dirac is in an insulating state. This is Mode I.

[0023] like Figure 3 As shown, in the 5.5~6.0THz band, the response of circularly polarized light is shown when the left Dirac is in an insulating state and the right Dirac is in a metallic state. This is Mode II.

[0024] like Figure 4 As shown, in the 5.5~6.0THz band, the response of different circularly polarized light when the left Dirac is in an insulating state and the right Dirac is in an insulating state is shown. This is Mode III.

[0025] like Figure 5 As shown, in the 5.5~6.0THz band, when the left Dirac is in a metallic state and the right Dirac is in an insulating state, it is Mode I, where the CD value reaches a maximum of 0.91. When the left Dirac is in an insulating state and the right Dirac is in a metallic state, it is Mode II, where the CD value reaches a maximum of -0.91. When both the left and right Diracs are in an insulating state, it is Mode III, which is the off state.

[0026] The above-described embodiments are merely illustrative of the present invention and are not intended to limit the scope of the present invention. Any equivalent modifications or improvements made by those skilled in the art to the technical solutions of the present invention without departing from the principles of the present invention shall be deemed to be within the protection scope of the present invention.

Claims

1. A chiral metasurface design based on Dirac dynamically tunable materials, characterized in that: The metasurface unit structure consists of three layers, from bottom to top: a silver substrate (3), BCB (2), and a top layer composed of a metal matrix ring split ring. The upper layer is Ag (3), and the lower layer is Dirac (1). The bottom layer is an Ag substrate with a fixed thickness of 0.6µm. The middle layer is a BCB dielectric material with a fixed thickness of 9µm. The outer ring of the top layer is made of Dirac material with a fixed thickness of 0.25µm. Other materials include P x and P y L1 is fixed at 28µm, L2 at 40µm, L3 at 44µm, and L3 at 7.8µm. W1, W2, and W3 are fixed at 2µm, 6.6µm, and 1.2µm, respectively.

2. The chiral metasurface design based on Dirac dynamically tunable materials according to claim 1, characterized in that: The substrate structure (3) in the structure is made of silver material with a fixed height of 0.6 μm.

3. The chiral metasurface design based on Dirac dynamically tunable materials according to claim 1, characterized in that: The intermediate layer in the structure is a BCB (2) dielectric material with a fixed height of 9 μm.

4. The chiral metasurface design based on Dirac dynamically tunable materials according to claim 1, characterized in that: The top rectangle is made of Dirac (1) material and has a fixed height of 0.25 μm.

5. The chiral metasurface design based on Dirac dynamically tunable materials according to claim 1, characterized in that: The top layer Ag(2) material has a fixed height of 0.25um.

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