A metasurface-based self-driven polarization detector and application

Abstract

The application discloses a kind of self-driven polarization detectors based on metasurface, belongs to polarization detection technical field.Self-driven polarization detector based on metasurface, including substrate, the upper surface of substrate is provided with several metasurface structure units, metasurface structure unit includes metal patch and bottom patch, metal patch is located above bottom patch, metal patch has non-centrosymmetric structure.Metal patch is Y type metal patch, the material of Y type metal patch is gold, the material of bottom patch is graphene.The self-driven polarization detector based on metasurface and application described in the application, when polarized light is irradiated to the surface of detector, gold-graphene metasurface will produce similar vector photoelectric current with displacement current, according to the difference of photoelectric current size and direction, realize the detection to polarized light, with the advantages of small volume, high degree of integration.

Description

Technical Field

[0001] This invention relates to the field of polarization detection technology, and in particular to a self-driven polarization detector based on metasurfaces and its applications. Background Technology

[0002] The wavelength range of mid-infrared electromagnetic waves is 2.5-25 μm. With the development of mid-infrared science, mid-infrared technology has shown broad application prospects in fields such as solar energy collection, guidance systems, and security monitoring. Self-driven polarization photodetector is a typical example of multi-dimensional optical field information application, and polarization detection in the mid-infrared band is a hot topic in mid-infrared science and technology research. Traditional polarization photodetector devices suffer from problems such as large size, difficulty in integration, and unremarkable performance.

[0003] The bulk photovoltaic effect (BPVE) is a nonlinear optical phenomenon prevalent in non-centrosymmetric materials. It spontaneously leads to the separation of photogenerated electrons and holes, generating a directional photocurrent, without the need for an external electric field. Due to the spontaneous polarization of non-centrosymmetric materials, BPVEs typically exhibit dependence on the polarization state of light, thus they are frequently used in polarization photodetector research. However, the self-driven photocurrent generated by BPVEs in conventional materials is usually small. Recent theoretical studies indicate that the high electronic state density and band Berry-related displacement current in low-dimensional material systems, combined with the strong absorption capacity of metallic metamaterials for incident electromagnetic waves, will be key to enhancing BPVEs.

[0004] Metamaterials are artificial composite materials. By controlling parameters such as the geometry and arrangement of metamaterial structural units, the polarization state and wavelength of incident electromagnetic waves can be detected. The combination of low-dimensional semiconductors and artificial metamaterials can simplify the integrated manufacturing process of polarization detectors, improve the photon coupling and quantum conversion efficiency of detectors, and bring new development opportunities to polarization detection technology. Summary of the Invention

[0005] The purpose of this invention is to provide a self-driven polarization detector based on a metasurface and its application. When polarized light is irradiated onto the detector surface, the gold-graphene metasurface generates a vector photocurrent similar to a displacement current. Based on the difference in the magnitude and direction of the photocurrent, the polarized light can be detected. It has the advantages of small size and high degree of integration.

[0006] To achieve the above objectives, the present invention provides a self-driven polarization detector based on metasurfaces, including a substrate, wherein a plurality of metasurface structural units are disposed on the upper surface of the substrate, the metasurface structural units including a metal patch and a bottom patch, the metal patch being located above the bottom patch, and the metal patch having a non-centrosymmetric structure.

[0007] Preferably, the metasurface structural units are distributed in a rectangular array on the upper surface of the substrate.

[0008] Preferably, the metal patch is a Y-shaped metal patch symmetrically placed along the Y-axis, and the Y-shaped metal patch is located at the center of the upper surface of the bottom patch.

[0009] Preferably, the Y-shaped metal patch has a width w of 0.1 μm, a length L1 of 0.5 μm, a length L2 of 0.6 μm, and a thickness of 60 nm.

[0010] Preferably, the opening angle φ of the Y-shaped metal patch is 0.1°-180°.

[0011] Preferably, the Y-shaped metal patch is made of gold with a purity of not less than 99.99%.

[0012] Preferably, the material of the bottom patch is graphene, which consists of a single layer of tightly packed carbon atoms.

[0013] Preferably, the bottom patch has a rectangular structure, with a width Px of 1.6 μm and a length Py of 1.8 μm.

[0014] Preferably, the substrate is made of silicon dioxide with a mid-infrared refractive index of 1.5 and a thickness of 300 nm.

[0015] The aforementioned metasurface-based self-driven polarization detector is applied in mid-infrared polarization light detection.

[0016] The advantages and positive effects of the self-driven polarization detector based on metasurface described in this invention and its applications are as follows:

[0017] 1. The detector of this invention is equipped with a "Y"-shaped metal patch antenna and a graphene underlayer patch. When polarized light shines on the detector, the non-centrosymmetric structure of the "Y"-shaped metal patch antenna can break the symmetry of the local electromagnetic field. Simultaneously, due to the difference in Seebeck coefficients between the metal and graphene materials, photogenerated carriers can be directionally transported under the drive of the asymmetric electromagnetic field, thereby forming a vector photocurrent. The direction and magnitude of this current are related to the polarization state of the incident light. Based on the difference in the magnitude and direction of the vector photocurrent, the electric field strength and polarization state of the polarized light can be deduced, enabling the detection of polarized light.

[0018] 2. The detector substrate of this invention has a thickness of 300 nm, the graphene patch has a width Px of 1.6 μm and a length Py of 1.8 μm. The detector is integrated at the micrometer scale, which has the advantages of high integration and small size. The detector described in this invention can simultaneously detect the intensity of mid-infrared incident electromagnetic waves and the polarization stage, and has the characteristics of compact structure, high flexibility, and adjustableness.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the detector structure according to an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of a metasurface structure unit according to an embodiment of the present invention;

[0022] Figure 3 The absorption spectrum of the "Y"-shaped metal patch antenna under x- and y-direction polarized light illumination is shown in the present invention when the aperture angle φ is 60°.

[0023] Figure 4 This invention describes the variation of the x-direction photocurrent Jx and y-direction photocurrent Jy (scalar projection values ​​of vector currents in the x and y directions) with the polarization angle θ (angle with the x-direction) of a "Y"-type metal patch antenna under x-direction polarized light illumination at a wavelength of 3.3 μm and an opening angle φ of 60°.

[0024] Figure 5 This is a top view of the normalized near-field profile and photocurrent distribution of the metasurface structure unit of the present invention under illumination of x-polarized light with a wavelength of 3.3 μm; when the aperture angle φ of the "Y"-shaped metal patch antenna is 60°.

[0025] Figure 6 This is a top view of the normalized near-field profile and photocurrent distribution of the metasurface structure unit of the present invention under illumination with 3.3 μm wavelength, y-direction polarized light, and with an aperture angle φ of 60° for the "Y"-shaped metal patch antenna.

[0026] Figure 7 The figure shows the elliptic curves of Jx and Jy of the "Y"-shaped metal patch antenna under x-direction polarized light illumination at a wavelength of 3.3 μm, with an opening angle φ of 60°, a length L2 of 0.6 μm, and lengths L1 of 0.1 μm, 0.3 μm, 0.5 μm, and 0.7 μm respectively.

[0027] Figure 8 The figure shows the elliptic curves of Jx and Jy of the "Y"-shaped metal patch antenna with length L1 of 0.5 μm, length L2 of 0.6 μm, and opening / closing angles φ of 0°, 60°, 120°, and 180° under x-direction polarized light illumination at a wavelength of 3.3 μm.

[0028] Figure 9The figure shows the elliptic curves of Jx and Jy of the "Y"-shaped metal patch antenna under x-direction polarized light illumination with wavelength of 3.3 μm and power of 1 W, 2 W and 5 W respectively, when the aperture angle φ is 60°.

[0029] Figure Labels

[0030] 1. Substrate; 2. Bottom layer patch; 3. Metal patch. Detailed Implementation

[0031] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] like Figure 1 As shown. A self-driven polarization detector based on metasurfaces includes a substrate 1, on the upper surface of which a plurality of metasurface structural units are disposed. The metasurface structural units are distributed in a rectangular array on the upper surface of the substrate 1, and the metasurface structural units are arranged closely without overlapping on the substrate 1.

[0034] like Figure 2 As shown. The metasurface structural unit includes a metal patch 3 and a bottom patch 2, with the metal patch 3 located above the bottom patch 2. The metal patch 3 has a non-centrosymmetric structure.

[0035] The metal patch 3 is a Y-shaped metal patch 3 placed symmetrically along the Y-axis direction, and the Y-shaped metal patch 3 is located at the center of the upper surface of the bottom patch 2.

[0036] The Y-shaped metal patch 3 has a width w of 0.1 μm, a length L1 of 0.5 μm, a length L2 of 0.6 μm, and a thickness of 60 nm.

[0037] The opening angle φ of the Y-type metal patch 3 is 0.1°-180°.

[0038] The Y-shaped metal patch 3 is made of gold with a purity of not less than 99.99%.

[0039] The Y-shaped metal patch antenna uses the relative permittivity defined by the Drud-Lorentz model within its operating band, with the equation being: The collision frequency plasma frequency 1.37×10 16 .

[0040] The material of the bottom patch 2 is graphene, which consists of a single layer of tightly packed carbon atoms.

[0041] The bottom patch 2 has a rectangular structure with a width Px of 1.6 μm and a length Py of 1.8 μm.

[0042] The refractive index of graphene in the operating wavelength range is referenced from the COMSOL Multiphysics 6.0 material library. The collective behavior of charge carriers in graphene is described using hydrodynamic equations, namely: ， The dynamic viscosity of the graphene electron flow is The density of electron flow in graphene .

[0043] The non-centrosymmetric structure of the "Y"-shaped metal patch 3-antenna can break the symmetry of the local electromagnetic field, allowing excited charge carriers to gain momentum. The difference in Seebeck coefficient between the "Y"-shaped metal patch 3-antenna and the graphene material creates a Seebeck coefficient gradient in space. Due to the local plasmon resonance effect near the metal structure under illumination, the electric field intensity is high at the edge of the "Y"-shaped metal patch 3-antenna, and photogenerated charge carriers form a local photocurrent driven by the Seebeck coefficient gradient. The local photocurrent establishes an electric field throughout the metasurface, driving charge carriers to form a directional photocurrent. By detecting the magnitude and direction of the photocurrent, the intensity and polarization state of polarized light can be detected in the mid-infrared band.

[0044] The substrate 1 is made of silicon dioxide with a refractive index of 1.5 in the mid-infrared band and a thickness of 300 nm.

[0045] This invention uses the multiphysics simulation software COMSOL Multiphysics 6.0 for simulation.

[0046] Figure 3 This is the absorption spectrum of the "Y"-shaped metal patch 3-antenna with an aperture angle φ of 60° under x- and y-direction polarized light illumination, according to the present invention. Figure 3As shown, the resonant absorption peak is at 3.3 μm. The model with these parameters is best suited for detecting linearly polarized light with a wavelength of 3.3 μm. Therefore, in subsequent simulations, light with a wavelength of 3.3 μm was used to illuminate the model. For linearly polarized light of other wavelengths, the detection of the incident light wavelength can be achieved by adjusting the parameters.

[0047] Figure 4 This invention relates to the variation of the x-direction photocurrent Jx and y-direction photocurrent Jy (the scalar projection values ​​of the vector currents in the x and y directions) with the polarization angle θ (the angle with the x-direction) of a "Y"-shaped metal patch 3-antenna under x-direction polarized light illumination at a wavelength of 3.3 μm and an aperture angle φ of 60°. Jx is symmetric about θ=90°, and Jy is antisymmetric about θ=90°, which conforms to the symmetry of the above model about the y-direction.

[0048] Figure 5 This is a top view of the normalized near-field profile and photocurrent distribution of the metasurface structure unit of the present invention under x-axis polarized light illumination at a wavelength of 3.3 μm. The aperture angle φ of the "Y"-shaped metal patch 3-antenna is 60°. From... Figure 5 As can be seen from this, after normalization, J x J is 0 y The value is 0.57. The difference between Jy and Jx is 0.57.

[0049] Figure 6 This is a top view of the normalized near-field profile and photocurrent distribution of the metasurface structure unit of the present invention under illumination with 3.3 μm wavelength, y-direction polarized light, with an aperture angle φ of 60° for the "Y"-shaped metal patch 3-antenna. From Figure 6 As can be seen from this, after normalization, J x =0, J y The value is 0.12. The difference between Jy and Jx is 0.12. The flow direction of the near-field photocurrent indicates that the flow of charge carriers in the bottom patch 2 is viscous, and the current exhibits fluid properties. Based on the difference between Jy and Jx under different polarized light incident directions, the polarization direction of the incident light can be detected.

[0050] Figure 7 The figure shows the elliptic curves of Jx and Jy of the "Y"-shaped metal patch 3-antenna with an opening angle φ of 60°, a length L2 of 0.6 μm, and lengths L1 of 0.1 μm, 0.3 μm, 0.5 μm, and 0.7 μm, respectively, under the illumination of x-direction polarized light with a wavelength of 3.3 μm. Figure 8This is an elliptic curve diagram of Jx and Jy for the "Y"-shaped metal patch 3-antenna with lengths L1 (0.5 μm), L2 (0.6 μm), and opening / closing angles φ (0°, 60°, 120°, and 180°) under x-axis polarized light illumination at a wavelength of 3.3 μm. The detector's J... x and J y The corresponding ellipse equation can be established. ,in a arrive e These are constants related to the sine equation. For polarized light with a wavelength of 3.3 μm and polarization in the x-direction, the optimal detection parameters are a length L1 of 0.5 μm, a length L2 of 0.6 μm, and an opening angle φ of 60°. For incident light of different wavelengths, polarization states, and polarization angles, the purpose of polarized light detection can be achieved by adjusting parameters such as the opening angle φ.

[0051] Figure 9 This is an elliptic curve of Jx and Jy for the "Y"-shaped metal patch 3-antenna with an aperture angle φ of 60°, under x-direction polarized light illumination at wavelengths of 3.3 μm and powers of 1 W, 2 W, and 5 W respectively. The detector's J... x and J y The elliptic curve is magnified proportionally with the increase of incident light power.

[0052] Therefore, by employing the self-driven polarization detector based on metasurface described in this invention, when polarized light irradiates the detector surface, the gold-graphene metasurface will generate a vector photocurrent similar to the displacement current. Based on the difference in the magnitude and direction of the photocurrent, the polarized light can be detected, which has the advantages of small size and high degree of integration.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A metasurface-based self-driven polarization detector, characterized in that: The substrate is provided with a plurality of metasurface structure units on the upper surface, the metasurface structure unit comprises a metal patch and a bottom patch, the metal patch is located above the bottom patch, and the metal patch has a non-centrosymmetric structure; The metal patch is a Y-shaped metal patch symmetrically arranged along the Y-axis direction, and the Y-shaped metal patch is located at the center of the upper surface of the bottom patch; The width w of the Y-shaped metal patch is 0.1 μm, the length L1 is 0.5 μm, the length L2 is 0.6 μm, and the thickness is 60 nm; The opening angle of the Y-shaped metal patch is 60°; The material of the bottom patch is graphene formed by closely arranging single-layer carbon atoms; The material of the Y-shaped metal patch is gold, and the purity of the gold is not less than 99.99%; The material of the substrate is silicon dioxide, the refractive index of the medium infrared wave band is 1.5, and the thickness of the substrate is 300 nm.

2. The metasurface-based self-driven polarization detector of claim 1, wherein: The metasurface structure units are distributed in a rectangular array on the upper surface of the substrate.

3. The metasurface-based self-driven polarization detector of claim 1, wherein: The bottom patch is a rectangular structure, the width Px of the bottom patch is 1.6 μm, and the length Py is 1.8 μm.

4. Application of the self-driven polarization detector based on the metasurface according to any one of claims 1-3 in the detection of polarized light in the medium infrared wave band.

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