Metasurface absorber based on metal-dielectric material and disc array structure

Abstract

The invention discloses a metasurface absorber based on a metal-dielectric material and a disc array structure, and the metasurface absorber consists of a substrate, a metal and dielectric layer plated on the substrate, and a double-disc array etched on the metal dielectric layer. Wherein the metal dielectric layer is composed of a silver reflecting layer with the thickness being 150 nm and a germanium layer with the thickness being 300 nm, the silver reflecting layer and the germanium layer are sequentially plated on the substrate, a single structural unit in the double-disc array is composed of two germanium discs with the heights being 150 nm and the radiuses being 2 microns and 2.5 microns respectively, the distance between the two germanium discs is 1.7 microns, the transverse period of the double-disc array is 12.4 microns, and the thickness of the double-disc array is 1.5 microns. And the longitudinal period of the double-disc array is 7 microns. The invention designs a selective wave band metasurface absorber which is irrelevant to a substrate and has good adaptability to an application environment. The metasurface absorber can still keep the designed spectral absorption performance under the conditions of a wide incident angle and different polarization.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical metasurfaces, and in particular relates to a metasurface absorber based on metal-dielectric materials and a disk array structure. Background Art

[0002] With the development of detection technology, more and more infrared detection equipment is used in the battlefield, posing a greater threat to the safety of personnel and weapons and equipment. The use of anti-detection devices on the battlefield has become an important means of protecting personnel and facilities. The research on efficient infrared stealth technology has become a hot field of research. To achieve efficient stealth performance, it is necessary to consider the emissivity of the surface of the object and the actual temperature of the object at the same time. On the one hand, the infrared radiation characteristics can be reduced by reducing the emissivity of the surface of the object; on the other hand, if the actual temperature of the object needs to be reduced, the emissivity of the surface of the object needs to be increased. In the early days, people covered the object with a metal film to reduce the emissivity, but due to the low overall emissivity, the actual temperature of the object would rise sharply, thereby enhancing the radiation energy and reducing the camouflage efficiency. According to Kirchhoff's law, for an object in thermal equilibrium, its emissivity is equal to the absorptivity. Adjusting the emissivity of the surface of the object is to adjust its surface absorptivity.

[0003] In order to achieve infrared stealth and have a certain heat dissipation capacity, in addition to achieving low emission in the atmospheric window, high emission should be achieved in the non-atmospheric window band to dissipate heat for the object, that is, low emission should be achieved in the 3~5μm and 8~14μm bands for infrared stealth, and high emission should be achieved in the 5~8μm band for heat dissipation. In addition, the infrared selective emitter should have good stability, angle and polarization insensitivity, etc., which are necessary conditions to ensure the efficient working performance of the infrared emitter. The substrate-independent performance can make the absorber have more flexible and varied practical applications. Summary of the invention

[0004] The purpose of the present invention is to provide a metasurface absorber based on metal-dielectric material and disk array structure with selective band thermal emission performance. Since the metasurface absorber selects metal material as the reflective layer and the reflective layer has only a flattened thin film structure, the metasurface absorber has no dependence on the substrate. Whether it is on a silicon substrate or a glass substrate (even a flexible material substrate), it can achieve an average thermal emissivity of up to 74.17% in the entire non-atmospheric window wavelength range of 5≤λ≤8, and the highest thermal emissivity exceeds 99%. It can achieve an average absorption rate of 20.86% in the wavelength range of 3≤λ<5μm, and an average absorption rate of 0.5% in the wavelength range of 8<λ≤14μm. In addition, the metasurface absorber designed by the present invention has good selective thermal emission performance under wide incident angles and different polarized light.

[0005] The present invention adopts the following technical scheme to achieve the above-mentioned purpose, which is a metasurface absorber based on metal-dielectric material and disk array structure, characterized in that: the metasurface absorber is composed of a substrate, a metal and dielectric layer plated on the substrate, and a double disk array etched on the dielectric layer, wherein the metal and dielectric layers are composed of a silver reflection layer with a thickness of 150nm and a germanium layer with a thickness of 300nm plated on the substrate in sequence, a single structural unit in the double disk array is composed of two germanium material disks with a height of 150nm and a radius of 2μm and 2.5μm respectively, the spacing between the two germanium material disks is 1.7μm, the lateral period of the double disk array is 12.4μm, and the longitudinal period of the double disk array is 7μm. The metasurface absorber achieves an average emissivity of up to 74.17% in the wavelength range of 5≤λ≤8μm, an average absorptivity of 20.86% in the wavelength range of 3≤λ<5μm, and an average absorptivity of 0.5% in the wavelength range of 8<λ≤14μm.

[0006] It is further defined that the substrate is a silicon substrate or a glass substrate.

[0007] Compared with the prior art, the present invention has the following advantages: the present invention proposes a metasurface absorber with a band-selective thermal emitter that is independent of the substrate and has good heat dissipation performance. The metasurface absorber can still maintain selective thermal emission performance and low emissivity performance in non-atmospheric windows under wide incident angles and different polarization conditions. An average thermal emissivity of up to 74.17% can be achieved in the wavelength range of 5≤λ≤8μm, and the highest thermal emissivity exceeds 99.5%. An average low emissivity of about 0.5% can be achieved in the wavelength range of 8<λ≤14μm in the atmospheric window, and an average emissivity of 20.86% can be achieved in the wavelength range of 3≤λ<5μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Schematic diagram of the three-dimensional structure of the metasurface absorber Figure 2 It is a schematic diagram of the two-dimensional structure of the metasurface absorber.

[0009] Figure 3 It is the absorption spectrum of the metasurface absorber.

[0010] Figure 4 It is the absorption spectrum of the metasurface absorber (here taking the glass substrate as an example) under incident light of different angles (0°, 15° and 30°) and different polarizations (S polarization and P polarization).

[0011] Figure 5 This is a comparison chart of the heat dissipation effect of the metasurface absorber (here taking the glass substrate as an example) and different surfaces at the same temperature. DETAILED DESCRIPTION

[0012] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0013] The metasurface absorber designed in the present invention has a selective band absorption range, achieving an average emissivity of up to 74.17% in the wavelength range of 5≤λ≤8μm, an average absorption rate of 20.86% in the wavelength range of 3≤λ<5μm, and an average absorption rate of 0.5% in the wavelength range of 8<λ≤14μm.

[0014] At the beginning of the design, we first selected a suitable thin film structure within the required spectral range. Considering that the commonly used metal-dielectric material-metal structure will produce additional absorption peaks in the long-wave infrared, this design finally chose a metal-dielectric structure, in which Ag is the metal reflective layer and Ge is the dielectric layer. Both Ag and Ge materials were evaporated by electron beam thermal evaporation, with evaporation rates of 2.5Å / S and 3Å / S, respectively.

[0015] The metasurface absorber based on metal-dielectric material and disk array structure of the present invention is composed of a substrate, a metal and dielectric layer plated on the substrate, and a double disk array etched on the dielectric layer, wherein the reflective layer is a metal silver film layer, and the germanium layer and the double disk array together constitute a germanium film layer. During the film coating process, quartz crystal monitoring is used to control the film thickness deposition error, thereby obtaining a result closer to the design. The surface structure is etched using an ion beam etcher, and the overall metasurface structure is optimized by simulation software design, and the film system structure is obtained as follows: Substrate / Ag / Ge / Air Among them, Ag is a silver (Ag) film with a thickness of 150nm, Ge is a germanium (Ge) film with a thickness of 300nm, and a germanium (Ge) double disk array with radii of 2μm and 2.5μm respectively, and the height of the two disks is 150nm; the substrate is a one-inch round substrate made of silicon substrate or glass substrate.

[0016] The obtained supersurface structure is: The double disk array has a lateral period of 12.4μm and a longitudinal period of 7μm. The radii of the two disks are 2μm and 2.5μm respectively, and the spacing between the two disks is 1.7μm.

[0017] Because the structure includes a 150nm silver reflective layer, the choice of substrate has no effect on the absorption spectrum. The metasurface absorber designed by the present invention has a high absorption rate, that is, a high emissivity effect in the wavelength spectrum range of 5≤λ≤8μm. In this wavelength range, an average absorption rate of 74.17% is achieved, and the highest absorption rate exceeds 99.5%. In the wavelength range of 3≤λ<5μm, an average absorption rate of 20.86% is achieved, and in the wavelength range of 8<λ≤14μm, an average absorption rate of 0.5% is achieved. Therefore, the metasurface absorber designed by the present invention obviously has selective thermal emission performance. Figure 4 It can be seen from the figure that the metasurface absorber designed by the present invention can maintain good absorption performance in the 5-8 μm band under different incident angles and different polarizations. Figure 5 It can be seen that the absorber designed by the present invention has good heat dissipation performance at different temperatures.

[0018] The basic principles, main features and advantages of the present invention are shown and described above. Without departing from the spirit and scope of the present invention, the present invention may also be subject to various changes and improvements, which all fall within the scope of the present invention to be protected.

Claims

1. A metasurface absorber based on metal-dielectric material and disk array structure, characterized in that: The metasurface absorber consists of a substrate, metal and dielectric layers plated on the substrate, and a double disk array etched on the dielectric layer, wherein the metal and dielectric layers consist of a silver reflective layer with a thickness of 150 nm and a germanium dielectric layer with a thickness of 300 nm plated on the substrate in sequence. A single structural unit in the double disk array consists of two germanium disks with a height of 150 nm and a radius of 2 μm and 2.5 μm respectively. The spacing between the two germanium disks is 1.7 μm, the lateral period of the double disk array is 12.4 μm, and the longitudinal period of the double disk array is 7 μm. The metasurface absorber achieves an average emissivity of up to 74.17% in the wavelength range of 5≤λ≤8μm, an average absorption rate of 20.86% in the wavelength range of 3≤λ<5μm, and an average absorption rate of 0.5% in the wavelength range of 8<λ≤14μm.

2. The metasurface absorber based on metal-dielectric material and disk array structure according to claim 1, characterized in that: The substrate is a silicon substrate or a glass substrate.

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