Self-driven polarization detector based on metasurface and application

Abstract

The invention discloses a self-driven polarization detector based on a metasurface, and belongs to the technical field of polarization detection. The self-driven polarization detector based on the metasurface comprises a substrate, a plurality of metasurface structure units are arranged on the upper surface of the substrate, each metasurface structure unit comprises a metal patch and a bottom patch, the metal patch is located above the bottom patch, and the metal patch is of a non-centrosymmetric structure. The metal patch is a Y-shaped metal patch, the Y-shaped metal patch is made of gold, and the bottom patch is made of graphene. According to the self-driven polarization detector based on the metasurface and the application, when polarized light irradiates the surface of the detector, the gold-graphene metasurface can generate vector light current similar to displacement current, detection of the polarized light is achieved according to the difference of the size and the direction of the light current, and the self-driven polarization detector has the advantages of being small in size and high in integration degree.

Description

Technical Field

[0001] The present invention relates to the field of polarization detection technology, and in particular to a self-driven polarization detector based on a metasurface and its application. Background Art

[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 the fields of solar energy collection, guidance systems, security monitoring, etc. Self-driven polarization photoelectric detection is a typical case of multi-dimensional light field information application, and polarization detection in the mid-infrared band is a hot topic in mid-infrared science and technology research. Traditional polarization photoelectric detection devices have problems such as large size, difficulty in integration, and poor performance.

[0003] Bulk photovoltaic effect (BPVE) is a nonlinear optical phenomenon that is common in non-centrosymmetric materials. It can spontaneously cause the separation of photogenerated electrons and holes without an external electric field, thereby generating a directional photocurrent. Since non-centrosymmetric materials have the characteristics of spontaneous polarization, BPVE usually shows dependence on the polarization state of light, so BPVE is often used in the study of polarization photodetection. However, the self-driven photocurrent generated by conventional materials based on BPVE is usually small. Recent theoretical studies have pointed out that the high electronic state density and band Berry-related displacement current in low-dimensional material systems, combined with the strong absorption ability of metal metamaterials for incident electromagnetic waves, will be the key to enhancing BPVE.

[0004] Metamaterials are artificial composite materials. By adjusting the geometric configuration 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 polarized light detectors, improve the photon coupling and quantum conversion efficiency of light detectors, and bring new development opportunities for polarized light detection technology. Summary of the invention

[0005] The purpose of the present 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 will generate a vector photocurrent similar to the displacement current. According to the difference in the size and direction of the photocurrent, the detection of polarized light is realized. It has the advantages of small size and high degree of integration.

[0006] To achieve the above-mentioned purpose, the present invention provides a self-driven polarization detector based on a metasurface, comprising a substrate, wherein a plurality of metasurface structure units are arranged on the upper surface of the substrate, the metasurface structure units include a metal patch and a bottom layer patch, the metal patch is located above the bottom layer patch, and the metal patch has a non-centrally symmetrical structure.

[0007] Preferably, the supersurface structure 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 direction, 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 material of the Y-shaped metal patch is gold, and the purity of the gold is not less than 99.99%.

[0012] Preferably, the material of the bottom patch is graphene composed of a single layer of closely arranged carbon atoms.

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

[0014] Preferably, the material of the substrate is silicon dioxide, the refractive index in the mid-infrared band is 1.5, and the thickness of the substrate is 300 nm.

[0015] The above-mentioned metasurface-based self-driven polarization detector is used in the detection of polarized light in the mid-infrared band.

[0016] The advantages and positive effects of the self-driven polarization detector based on the metasurface and its application described in the present invention are: 1. The detector of the present invention is provided with a "Y"-shaped metal patch antenna and a graphene bottom patch. When polarized light is irradiated to the detector, the non-centrosymmetric structure of the "Y"-shaped metal patch antenna can break the symmetry of the local electromagnetic field. At the same time, due to the difference in Seebeck coefficients of metal and graphene materials, photogenerated carriers can be transmitted in a direction driven by the asymmetric electromagnetic field, thereby forming a vector photocurrent. The direction and magnitude of the current are related to the polarization state of the incident light. According to the difference in magnitude and direction of the vector photocurrent, the electric field intensity and polarization state of the polarized light can be reversely deduced to achieve the detection of polarized light.

[0017] 2. The thickness of the detector substrate of the present invention is 300nm, the width Px of the graphene patch is 1.6 μm, and the length Py is 1.8 μm. The detector is integrated at a micron size, which has the advantages of high integration and small size. The detector of the present invention can realize the simultaneous detection of the intensity of the incident mid-infrared electromagnetic wave and the polarization table, and has the characteristics of compact structure, strong flexibility, and controllability.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the detector structure of an embodiment of the present invention; Figure 2 Schematic diagram of a super surface structure unit according to an embodiment of the present invention; Figure 3 The absorption spectrum of the "Y"-shaped metal patch antenna of the present invention when the opening angle φ is 60° under the irradiation of polarized light in the x-direction and the y-direction; Figure 4 The present invention shows the changes of the x-direction photocurrent Jx and the y-direction photocurrent Jy (the scalar projection values ​​of the vector current in the x-direction and the y-direction) with the polarization angle θ (the angle with the x-direction) when the opening angle φ of the "Y"-shaped metal patch antenna is 60° under the irradiation of the x-direction polarized light with a wavelength of 3.3 μm; Figure 5 It is a top view of the normalized near-field profile and photocurrent distribution of the metasurface structure unit of the present invention when the opening angle φ of the "Y"-shaped metal patch antenna is 60° under the irradiation of polarized light in the x direction with a wavelength of 3.3 μm; Figure 6 It is a top view of the normalized near-field profile and photocurrent distribution of the metasurface structure unit of the present invention when the opening angle φ of the "Y"-shaped metal patch antenna is 60° under the irradiation of polarized light in the y direction with a wavelength of 3.3 μm; Figure 7 The elliptic curve diagram of Jx and Jy when the opening angle φ of the "Y"-shaped metal patch antenna is 60°, the length L2 is 0.6 μm, and the length L1 is 0.1 μm, 0.3 μm, 0.5 μm, and 0.7 μm respectively under the irradiation of polarized light in the x direction at a wavelength of 3.3 μm of the present invention; Figure 8 The elliptical curve diagram of Jx and Jy when the length L1 of the "Y"-shaped metal patch antenna is 0.5 μm, the length L2 is 0.6 μm, and the opening and closing angles φ are 0°, 60°, 120°, and 180°, respectively, under the irradiation of polarized light in the x direction at a wavelength of 3.3 μm of the present invention; Fig. 9 This is the elliptical curve diagram of Jx and Jy when the opening angle φ of the "Y"-shaped metal patch antenna is 60° under the irradiation of x-direction polarized light with a wavelength of 3.3 μm and powers of 1 W, 2 W, and 5 W respectively.

[0020] Reference numerals 1. Substrate; 2. Bottom patch; 3. Metal patch. DETAILED DESCRIPTION

[0021] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the invented product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, the terms "setting", "installation", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0023] like Figure 1 A self-driven polarization detector based on a metasurface includes a substrate 1, and a plurality of metasurface structural units are arranged on the upper surface of the substrate 1. 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 on the substrate 1 in a tight and non-overlapping manner.

[0024] like Figure 2 The metasurface structural unit includes a metal patch 3 and a bottom patch 2, wherein the metal patch 3 is located above the bottom patch 2. The metal patch 3 has a non-centrosymmetric structure.

[0025] The metal patch 3 is a Y-shaped metal patch 3 symmetrically placed 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 .

[0026] 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.

[0027] The opening angle φ of the Y-shaped metal patch 3 is 0.1°-180°.

[0028] The material of the Y-shaped metal patch 3 is gold, and the purity of gold is not less than 99.99%.

[0029] The relative dielectric constant of the Y-shaped metal patch 3 antenna is defined by the Drude-Lorentz model within the working band, and the equation is: , where the collision frequency , plasma frequency 1.37×1016 .

[0030] The material of the bottom patch 2 is graphene composed of a single layer of carbon atoms tightly arranged.

[0031] The bottom patch 2 is a rectangular structure, and the width Px of the bottom patch 2 is 1.6 μm and the length Py is 1.8 μm.

[0032] The refractive index of graphene in the working band is referenced from the COMSOL Multiphysics 6.0 material library. The fluid mechanics equation is used to describe the collective behavior of carriers in graphene. The equation is: ， The dynamic viscosity of graphene electron flow is , the density of electron flow in graphene .

[0033] The non-centrosymmetric structure of the "Y"-shaped metal patch 3 antenna can break the symmetry of the local electromagnetic field, allowing the excited carriers to gain momentum. The difference in Seebeck coefficients between the "Y"-shaped metal patch 3 antenna and the graphene material will form a Seebeck coefficient gradient in space. Due to the local plasmon effect near the metal structure under illumination, the electric field intensity at the edge of the "Y"-shaped metal patch 3 antenna is high, and the photogenerated carriers form a local photocurrent driven by the Seebeck coefficient gradient. The local photocurrent will establish an electric field in the entire metasurface, driving the carriers to form a directional photocurrent. By detecting the size and direction of the photocurrent, the purpose of detecting the intensity and polarization state of polarized light can be achieved in the mid-infrared band.

[0034] The material of the substrate 1 is silicon dioxide, the refractive index in the mid-infrared band is 1.5, and the thickness of the substrate 1 is 300 nm.

[0035] The present invention uses multi-physics field simulation software COMSOL Multiphysics 6.0 for simulation.

[0036] Figure 3 The absorption spectrum of the present invention when the opening angle φ of the "Y"-shaped metal patch 3 antenna is 60° under the irradiation of polarized light in the x-direction and y-direction. Figure 3 As shown in the figure, the resonance absorption peak is at 3.3μm. The model under this parameter is most suitable for detecting linearly polarized light with a wavelength of 3.3μm. Therefore, in the subsequent simulations, the above models are all irradiated with light with a wavelength of 3.3μm. For linearly polarized light of other wavelengths, the wavelength of the incident light can be detected by adjusting the parameters.

[0037] Figure 4The present invention shows that when the opening angle φ of the "Y"-shaped metal patch 3 antenna is 60° under the irradiation of polarized light in the x direction with a wavelength of 3.3 μm, the photocurrent Jx in the x direction and the photocurrent Jy in the y direction (the scalar projection value of the vector current in the x direction and the y direction) change with the polarization angle θ (the angle with the x direction). Jx is symmetric about θ=90°, and Jy is antisymmetric about θ=90°, which is consistent with the symmetry of the above model about the Y direction.

[0038] 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 when the opening angle φ of the "Y"-shaped metal patch 3 antenna is 60° under the irradiation of polarized light in the x direction with a wavelength of 3.3 μm. Figure 5 It can be seen that after normalization, J x is 0, J y The difference between Jy and Jx is 0.57.

[0039] 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 when the opening angle φ of the "Y"-shaped metal patch 3 antenna is 60° under the irradiation of polarized light in the y direction with a wavelength of 3.3 μm. Figure 6 It can be seen that after normalization, J x is 0, J y 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 carriers in the bottom patch 2 is viscous, and the current has the properties of a fluid. According to the difference between Jy and Jx under different directions of polarized light incident, the polarization direction of the incident light can be detected.

[0040] Figure 7 The elliptic curve diagram of Jx and Jy when the opening angle φ of the "Y"-shaped metal patch 3 antenna is 60°, the length L2 is 0.6 μm, and the length L1 is 0.1 μm, 0.3 μm, 0.5 μm, and 0.7 μm respectively under the irradiation of polarized light in the x direction at a wavelength of 3.3 μm of the present invention; Figure 8 The elliptic curves of Jx and Jy are shown in the figure below when the wavelength is 3.3 μm and the polarized light in the x direction is irradiated, and the length L1 of the “Y”-shaped metal patch 3 antenna is 0.5 μm, the length L2 is 0.6 μm, and the opening and closing angles φ are 0°, 60°, 120°, and 180°, respectively. x and J y The corresponding ellipse equation can be established, ,in a arrive eis a constant related to the sine equation. For the wavelength of 3.3 μm, polarized light in the x direction, the length L1 is 0.5 μm, the length L2 is 0.6 μm, and the opening and closing angle φ is 60°, which is the optimal detection parameter. 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 and closing angle φ.

[0041] Fig. 9 The elliptic curves of Jx and Jy are shown in the figure below when the opening angle φ of the Y-shaped metal patch 3 antenna is 60° under the irradiation of x-direction polarized light with a wavelength of 3.3 μm and powers of 1 W, 2 W, and 5 W, respectively. x and J y The elliptic curve graph is enlarged proportionally with the increase of incident light power.

[0042] Therefore, by using the metasurface-based self-driven polarization detector and application described in the present invention, when polarized light is irradiated onto the detector surface, the gold-graphene metasurface will generate a vector photocurrent similar to the displacement current, and the detection of polarized light can be achieved based on the difference in the size and direction of the photocurrent, which has the advantages of small size and high degree of integration.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A self-driven polarization detector based on metasurface, Features: It includes a substrate, and a plurality of super surface structure units are arranged on the upper surface of the substrate. The super surface structure units include a metal patch and a bottom patch. The metal patch is located above the bottom patch, and the metal patch has a non-centrally symmetrical structure.

2. A self-driven polarization detector based on a metasurface according to claim 1, Features: The super surface structural units are distributed in a rectangular array on the upper surface of the substrate.

3. The self-driven polarization detector based on a metasurface according to claim 1, Features: The metal patch is a Y-shaped metal patch symmetrically placed along the Y-axis direction, and the Y-shaped metal patch is located at the center of the upper surface of the bottom patch.

4. The self-driven polarization detector based on a metasurface according to claim 3, Features: 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.

5. The self-driven polarization detector based on a metasurface according to claim 3, Features: The opening angle φ of the Y-shaped metal patch is 0.1°-180°.

6. The self-driven polarization detector based on a metasurface according to claim 3, Features: The material of the Y-shaped metal patch is gold, and the purity of the gold is not less than 99.99%.

7. The self-driven polarization detector based on a metasurface according to claim 1, Features: The material of the bottom patch is graphene composed of a single layer of carbon atoms tightly arranged.

8. The self-driven polarization detector based on a metasurface according to claim 7, Features: The bottom patch is a rectangular structure, and the width Px of the bottom patch is 1.6 μm and the length Py is 1.8 μm.

9. The self-driven polarization detector based on a metasurface according to claim 1, Features: The material of the substrate is silicon dioxide, the refractive index in the mid-infrared band is 1.5, and the thickness of the substrate is 300nm.

10. Application of a self-driven polarization detector based on a metasurface according to any one of claims 1 to 9 in the detection of polarized light in the mid-infrared band.

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