A metamaterial selective absorber with high reflectivity in visible light and high absorption in mid-infrared

Abstract

The application discloses a selective metamaterial wave absorber with high reflection characteristics in a visible light band and high absorption characteristics in a middle infrared band, and relates to the technical field of functional optical metamaterials. The wave absorber is divided into three layers, the upper layer is a silicon dioxide pyramid body (1), the middle layer is a silicon dioxide film (2), and the lower layer is a metal film substrate (3). The upper layer silicon dioxide pyramid body (1), the middle layer silicon dioxide film (2) and the lower layer metal film substrate (3) form a basic unit, and the basic unit is periodically distributed in an x-y horizontal plane in an array. The reflectivity of the metamaterial wave absorber in the visible light band of 0.6-4.5 microns is greater than 0.9, and the absorption rate in the middle infrared band of 8-30 microns is greater than 0.9. The application has the advantages of simple structure, easy preparation, wide absorption bandwidth, excellent absorption effect and economic preparation, and can be applied to the fields of infrared detection, radiation refrigeration and the like.

Description

Technical Field

[0001] This invention relates to the field of functional optical metamaterials technology and applications, specifically a metamaterial selective absorber with high reflectivity in the visible light band and high absorption in the mid-infrared band. Background Technology

[0002] Metamaterials are artificial composite structures and materials possessing extraordinary physical properties not found in natural materials. They can overcome the limitations of natural materials, forming artificial structural materials with special electromagnetic characteristics. By controlling the microstructure of materials, selective metamaterial structures with high absorption or high reflection in specific wavelength bands can be created. Currently, metamaterials can be applied in electromagnetic, optical, acoustic, and thermal fields, in industries including communications, medical, aerospace, military, and integrated circuit (IC) industries, such as infrared radar, microwave absorbing materials, and textile coatings. In recent years, radiative cooling, as a passive, efficient, and renewable method for reducing energy consumption, has attracted widespread attention in the field of energy conservation. The principle of radiative cooling can be simplified to high reflection of electromagnetic waves in the visible light band and high absorption of electromagnetic waves in the mid-infrared band. Therefore, designing a metamaterial absorber with high reflection of visible light and high absorption of electromagnetic waves in the mid-infrared band is of great significance to the development of radiative cooling technology. Simultaneously, this metamaterial structure can also be used in sensor detection, nonlinear optics, and electromagnetic stealth technology.

[0003] Currently, researchers have proposed many metamaterial absorbing structures, but these structures have some drawbacks: they cannot achieve tunable broadband absorption, or the absorption bandwidth is narrow and difficult to adjust, or the proposed structures are composed of multiple layers of different materials, making fabrication cumbersome and costly. To address these problems, this invention designs a simple metamaterial broadband absorber that only requires etching of one material, making fabrication simple and economical. It achieves ultra-wideband absorption with a reflectivity greater than 90% in the visible light band and an absorptivity greater than 90% in the mid-infrared band, enabling radiative cooling under direct solar irradiation. Furthermore, this structure is robust; changes in structural dimensions within a certain range (increasing or decreasing) have little impact on the emission and absorption performance of the metamaterial absorber, reducing the requirements for fabrication processes.

[0004] The metamaterial absorber structure proposed in this invention overcomes the problems of complex structure, narrow absorption bandwidth, poor absorption effect and difficult preparation of previous technologies, and has broad application prospects. Summary of the Invention

[0005] To achieve high reflectivity in the visible light band and high absorption in the mid-infrared band, the present invention is as follows:

[0006] A three-dimensional metamaterial selective absorber exhibiting high reflectivity in the visible light band and high absorption in the mid-infrared band comprises a three-layer structure: an upper layer of silica pyramids (1), a middle layer of silica thin film (2), and a lower layer of metal thin film substrate (3). The upper silica pyramids (1), the middle silica thin film (2), and the lower metal thin film substrate (3) form the basic unit, which is periodically arrayed in the xy-plane. Figure 1 The diagram shows a top view of its three-dimensional structure and a schematic diagram of its basic units. The thickness of the silica pyramid (1) is shown. Its top x-direction width w ux =1μm~4μm, width w in the y direction uy =1μm~4μm, bottom x-direction width w lx =5μm~20μm, width w in the y direction ly =5μm~20μm, the spacing between the silicon dioxide pyramids is i=0μm~5μm, the thickness of the silicon dioxide film (2) is h s =0μm~40μm, metal thin film substrate (3) film thickness h Au =0.05μm~5μm, in Figure 1 , Figure 2 The corresponding positions in the diagram indicate the aforementioned structural parameters. Within the range described above, the height of the silica pyramid (1) is varied. Top width w ux and w uy Bottom width w lx and w ly 1. Change the spacing i between the silica pyramids (1) 2. Change the thickness h of the silica film (2) s 1. Change the film thickness h of the metal thin film substrate (3) Au These parameters can also achieve high reflectivity in the visible light band and high absorption in the mid-infrared band.

[0007] The material of the metal thin film substrate (3) can be gold, silver, copper, tungsten or aluminum, and the materials of the silicon dioxide pyramid (1) and the silicon dioxide thin film (2) can be replaced with aluminum oxide or glass.

[0008] The structural dimensions of different silica pyramid bodies (1) can vary slightly, which has little impact on the reflection, transmission and absorption performance of metamaterial absorbers.

[0009] The metamaterial structure designed in this invention has the following spectral absorption range: a reflectance greater than 0.9 in the visible light wavelength range of 0.6 micrometers to 4.5 micrometers, and an absorptivity greater than 0.9 in the mid-infrared band of 8 micrometers to 30 micrometers.

[0010] Compared with the prior art, the significant advantages of this invention are:

[0011] 1. The metamaterial absorber proposed in this invention uses only one material for the upper and middle layers. Compared with the previous multi-layered complex structures, this invention greatly reduces the complexity of the structure, which makes the preparation process relatively simple, while maintaining good absorption and reflection effects.

[0012] 2. Compared with previously proposed structures, the metamaterial absorber proposed in this invention effectively suppresses the absorption of electromagnetic waves in the 0.6-micrometer to 4.5-micrometer band, while achieving near-perfect broadband absorption of electromagnetic waves in the 8-micrometer to 30-micrometer band.

[0013] 3. The metamaterial absorber proposed in this invention uses conventional and readily available materials, which are inexpensive, easy to implement, and economically viable.

[0014] 4. The metamaterial absorber proposed in this invention has structural robustness, which means that changes in the size of the structure within a certain range (increase or decrease) have little impact on the emission and absorption performance of the metamaterial absorber. Attached Figure Description

[0015] Figure 1 This is a top view of the three-dimensional structure of the metamaterial absorber of the present invention on the xy horizontal plane.

[0016] Figure 2 This is a side view of the metamaterial absorber structure of the present invention in the xz plane.

[0017] Figure 3 This is a schematic diagram of the absorption spectrum of the metamaterial absorber structure of the present invention in Example 1.

[0018] Figure 4 This is a schematic diagram of the absorption spectrum of the metamaterial absorber structure of the present invention in Example 2.

[0019] Figure 5 This is a schematic diagram of the absorption spectrum of the metamaterial absorber structure of the present invention in Example 3.

[0020] Figure 6 This is a schematic diagram of the absorption spectrum of the metamaterial absorber structure of the present invention in Example 4.

[0021] Figure 7 This is a schematic diagram of the absorption spectrum of the metamaterial absorber structure of the present invention in Example 5. Detailed Implementation

[0022] The present invention will be further described in conjunction with the following specific embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to the following embodiments. Those skilled in the art can readily modify the following examples and apply the general principles to other examples without inventive effort. Therefore, all modifications and improvements made to the present invention by those skilled in the art based on the description provided are within the scope of protection of the present invention, and are protected by the appended claims.

[0023] Example 1

[0024] The thickness of the silica pyramid (1) under parallel wave incident conditions. Its top width w ux =w uy = 1 micrometer, bottom width w lx =w ly =8 micrometers, spacing i =0 micrometers, thickness h of silicon dioxide thin film (2) s =1 micrometer, the material used for the metal thin film substrate (3) is gold, and its thickness h Au = 1 micrometer. The absorption spectrum of the proposed metamaterial absorber is as follows: Figure 3 As shown, the reflectivity is greater than 0.9 in the range of 0.6 micrometers to 4.5 micrometers, and the absorptivity is greater than 0.9 in the range of 8 micrometers to 30 micrometers.

[0025] Example 2

[0026] The thickness of the silica pyramid (1) under parallel wave incident conditions. Its top width w ux =w uy = 1 micrometer, bottom width w lx =w ly = 7.5 micrometers, spacing i = 0.5 micrometers, thickness h of silicon dioxide film (2) s =8 micrometers, the metal thin film substrate (3) is made of gold, and its thickness h Au =2 micrometers. The absorption spectrum of the proposed metamaterial absorber is as follows: Figure 4 As shown, it can be seen that the reflectivity in the range of 0.6 micrometers to 4.5 micrometers is also greater than 0.9, and the absorptivity in the range of 8 micrometers to 30 micrometers is also greater than 0.9. Therefore, by changing the structural dimensions and other parameters of the metamaterial absorber, as long as the basic unit composed of the upper silicon dioxide pyramid (1), the middle silicon dioxide film (2) and the lower metal film substrate (3) is arranged in an array periodic distribution on the xy horizontal plane, it is possible to achieve high reflectivity for electromagnetic waves with an incident range of 0.6 micrometers to 4.5 micrometers and high absorption for electromagnetic waves with an incident range of 8 micrometers to 30 micrometers.

[0027] Example 3

[0028] The thickness of the silica pyramid (1) under parallel wave incident conditions. Its top width w ux =w uy = 1.2 micrometers, bottom width w lx =w ly =8 micrometers, spacing i =0 micrometers, thickness h of silicon dioxide film (2) s =1 micrometer, the material used for the metal thin film substrate (3) is gold, and its thickness h Au = 1 micrometer. The absorption spectrum of the proposed metamaterial absorber is as follows: Figure 5 As shown, reducing the structural size of the invented metamaterial absorber to a certain range will have some impact on the absorption of electromagnetic wavelengths. The absorption rate decreases slightly near 15 micrometers, but it is still greater than 0.8. The impact on short-wavelength reflection is very small. Therefore, this example illustrates that changing the structural size of the proposed metamaterial absorber can still achieve the goal of high reflectivity in the visible light band and high absorption in the mid-infrared band.

[0029] Example 4

[0030] The thickness of the silica pyramid (1) under parallel wave incident conditions. Its top width w ux = 1.2 micrometers, w uy = 1 micrometer, bottom width w lx = 7.5 micrometers, w ly =7 micrometers, spacing i = 0.5 micrometers, thickness h of silicon dioxide film (2) s =2 micrometers, the material used for the metal thin film substrate (3) is gold, and its thickness h Au = 1 micrometer. The absorption spectrum of the proposed metamaterial absorber is as follows: Figure 6 As shown, the reflectivity is greater than 0.9 in the range of 0.6 micrometers to 4.5 micrometers, and the absorptivity is greater than 0.9 in the range of 8 micrometers to 30 micrometers. This example illustrates that when the top width and bottom width of the silica pyramid (1) are not equal, the effect on the absorption performance of the metamaterial absorber structure is also small, and the purpose of high reflectivity in the visible light band and high absorption in the mid-infrared band can still be achieved.

[0031] Example 5

[0032] Under parallel wave incidence, the silicon dioxide material is replaced with aluminum oxide (Al2O3). The aluminum oxide pyramid has a thickness of 54 micrometers and a top width of w. ux =w uy = 1 micrometer, bottom width w lx =w ly =7.5 micrometers, spacing i = 0.5 micrometers, thickness h of aluminum oxide film (2) s=5 micrometers, the gold material used in the metal thin film substrate (3) is replaced with silver material, and its thickness is 2 micrometers. The absorption spectrum of the proposed metamaterial absorber is as follows. Figure 7 As shown, the absorptivity is less than 0.1 in the range of 0.6 micrometers to 5 micrometers, and greater than 0.9 in the range of 9.2 micrometers to 26.5 micrometers. This example illustrates that when the materials constituting the metamaterial absorber are changed within the above material range, its high reflectivity in the visible light band and high absorption in the mid-infrared band remain essentially unchanged.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A metamaterial selective absorber exhibiting high reflectivity in the visible light and high absorption in the mid-infrared, comprising: The structure consists of three layers: the upper layer is a silicon dioxide pyramid (1), the middle layer is a silicon dioxide thin film (2), and the lower layer is a metal thin film substrate (3). Its features are as follows: the upper silicon dioxide pyramid body (1), the middle silicon dioxide thin film (2) and the lower metal thin film substrate (3) form a basic unit, which is arranged in an array periodically on the xy horizontal plane; Silica pyramid body (1) Thickness h SiO2 =57μm~100μm, its top x-direction width w ux =1μm~4μm, width w in the y direction uy =1μm~4μm, bottom x-direction width w lx =5μm~20μm, width w in the y direction ly =5μm~20μm, the spacing between the silicon dioxide pyramids is i=0μm~5μm, the thickness of the silicon dioxide film (2) is h s =0μm~40μm, metal thin film substrate (3) film thickness h Au =0.05μm~5μm.

2. The metamaterial selective absorber with high reflectivity in visible light and high absorption in mid-infrared light according to claim 1, characterized in that... The material of the metal thin film substrate (3) is gold, silver, copper, tungsten or aluminum, and the materials of the silicon dioxide pyramid (1) and the silicon dioxide thin film (2) can be replaced with aluminum oxide or glass.

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