Intermediate infrared absorber based on annular array metasurface

Abstract

The invention provides an intermediate infrared absorber based on an annular array metasurface, the intermediate infrared absorber is composed of a plurality of basic unit arrays with the same structure, and each basic unit comprises a bottom metal layer, a dielectric layer and a top metal layer; the dielectric layer is tightly attached to the bottom metal layer, the top metal layer on the upper portion of the dielectric layer is provided with annular titanium arrays of two sizes in a combined arrangement mode, and a row of large annular titanium and a row of small annular titanium are arranged at intervals in a staggered mode. And the circle center of each small annular titanium and the circle centers of the two nearest large annular titanium in the same adjacent row are respectively distributed on three corners of an equilateral triangle. Symmetrical design is adopted, so that the stability of the function of the super-surface absorber is ensured. The combination of the circular ring titanium metal layers with different sizes at the top reduces the number of design layers of a traditional metasurface, and simplifies the processing difficulty.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic detection technologies, and particularly to a mid-infrared absorber based on a ring-array metasurface. Background Art

[0002] The mid-infrared band is widely used in fields such as thermal imaging, environmental monitoring, gas detection, medical diagnosis, and military equipment. Highly sensitive detection in this band is crucial for identifying temperature distributions, gas compositions, and the thermal radiation characteristics of objects. A metasurface absorber is an artificial material that achieves efficient absorption of electromagnetic waves in a specific band through nanostructure design. By precisely designing the nanostructure, selective absorption of light or other electromagnetic waves of a specific wavelength can be achieved, thereby significantly improving the sensitivity of the detector and playing an important role in weak signal detection. Based on nanoscale design, the metasurface absorber can achieve an extremely thin structure, significantly reducing the volume and weight of the detector, which is particularly important for the development of portable and miniaturized mid-infrared detection devices. At the same time, it can achieve a higher level of conversion efficiency between the absorbed mid-infrared energy and other forms of energy (such as electrical and thermal signals), helping to improve the response speed and overall performance of the detector.

[0003] Currently, mid-infrared metasurface absorbers in the prior art usually only achieve efficient absorption within a specific band and it is difficult to cover the entire range of the 8 - 12 μm band. Most absorbers can only exhibit good absorption performance within a relatively narrow frequency band and cannot meet the demand for efficient absorption over a wide frequency band. Therefore, how to achieve efficient absorption over the entire range in the 8 - 12 μm band has become a key technical problem in improving the sensitivity, response speed, and overall performance of the detector. Summary of the Invention

[0004] To achieve the above object, the present invention provides a mid-infrared absorber based on a ring-array metasurface, which has a simple structure, high absorption efficiency, and is also convenient for micro-nano processing under high integration. This metasurface has excellent spectral selectivity and can achieve nearly perfect absorption under wide-angle incidence in the 8 - 12 μm range.

[0005] The implementation process of the present invention is as follows:

[0006] The mid-infrared absorber based on a ring-array metasurface is composed of an array of multiple identical basic units. Each basic unit includes a bottom metal layer, a dielectric layer, and a top metal layer;

[0007] The material of the bottom metal layer is titanium; the material of the dielectric layer is silicon, and the top metal layer is multiple annular titaniums;

[0008] The dielectric layer is close to the bottom metal layer, and the top metal layer above the dielectric layer has a combination of two sizes of annular titanium arrays, a row of large annular titanium and a row of small annular titanium are arranged at intervals, and the center of each small annular titanium and the center of the two nearest large annular titanium in the same row are respectively distributed at the three corners of an equilateral triangle.

[0009] The top metal layer of the present invention adopts a symmetrical design to ensure the stability of the super surface absorber function. The combination of the top titanium metal layer with different sizes of circular rings reduces the number of design layers of the traditional super surface and simplifies the processing difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a top view of the mid-infrared absorber based on the ring array metasurface;

[0011] Figure 2 It is a cross-sectional schematic diagram of a mid-infrared absorber based on a ring array metasurface;

[0012] Figure 3 The absorption spectrum of the metasurface absorber at normal incidence of 3-12 μm obtained by simulation calculation;

[0013] Figure 4 The absorption spectrum of the absorber at different incident angles obtained by simulation calculation;

[0014] Figure 5 The absorption spectrum of the absorber under different ambient refractive indices obtained by simulation calculation. DETAILED DESCRIPTION

[0015] like Figure 1 and Figure 2 As shown, a mid-infrared absorber based on a ring array metasurface, a bottom metal layer, a dielectric layer, and a top metal layer;

[0016] The material of the bottom metal layer is titanium; the material of the dielectric layer is silicon, and the top metal layer is a plurality of annular titanium; the dielectric layer is close to the bottom metal layer, and the top metal layer above the dielectric layer has an annular titanium array combination arrangement of two sizes, a row of large annular titanium and a row of small annular titanium are arranged at intervals and staggered, and the center of each small annular titanium is distributed at the three corners of an equilateral triangle with the center of the two nearest large annular titanium in the same adjacent row.

[0017] The dimensions of the basic unit structure after optimization by electromagnetic simulation software Ansys Lumerical FDTD are as follows (taking the minimum period as an example): the bottom layer is titanium metal, the unit size is 2.0*3.46μm, and the thickness is H1=0.3μm. The dielectric material is silicon layer, the unit size is 2.0*3.46μm, and the thickness is H2=0.62μm. The top layer is made of titanium rings of different sizes arranged in an alternating pattern, with the inner and outer diameters of the larger titanium rings being D1 = 0.3 μm, D 2 = 0.9 μm, thickness H 3 is 0.02 μm; the inner and outer radii of the smaller-sized titanium ring are r 1 = 0.2 μm, r 2 = 0.8 μm, and the thickness is 0.02 μm. The material parameters are from the palik material library in the FDTD software. The simulation is carried out with the minimum periodic structure, setting periodic boundary conditions along the X and Y directions, and then simulating the absorption spectra at different angles and different environmental refractive indices.

[0018] In this embodiment, the absorption spectrum obtained by FDTD simulation is as Figure 3 shown. The simulation results show that when the incident light with a wavelength of 3 - 14 μm is incident vertically, the absorption efficiency is generally high in the infrared window of 8 - 12 μm, and the absorption rate is even nearly 100% in some bands. The average absorption rate over the entire band exceeds 90%, approaching perfect absorption.

[0019] In this embodiment, through FDTD simulation calculation, the software simulations of the large-angle absorption performance of this absorber and the change of the application environment refractive index are also carried out respectively, as Figure 4 shown. The software simulates the basic influence of the oblique incidence of the incident light on the metasurface absorber. The simulation results show that this absorber can meet the situation of relatively large-angle incidence. The basic absorption curve is maintained in the range of 0° - 30° incident angle, and the absorption peak does not decrease significantly. When the incident light is at 70°, the absorption rate is still above 80% in some bands. As Figure 5 shown, when the background environmental refractive index increases from 1.0 to 1.5, the performance of this absorber remains basically unchanged, and the average absorption rate can be maintained above 90%. It shows that this absorber can be applied to the atmospheric environment in most cases.

Claims

1. The mid-infrared absorber based on the ring array metasurface is composed of multiple basic unit arrays with the same structure. It is characterized in that Each basic unit includes a bottom metal layer, a dielectric layer, and a top metal layer; The dielectric layer is close to the bottom metal layer, and the top metal layer above the dielectric layer has a combination of two sizes of annular titanium arrays, a row of large annular titanium and a row of small annular titanium are arranged at intervals, and the center of each small annular titanium and the center of the two nearest large annular titanium in the same row are respectively distributed at the three corners of an equilateral triangle.

2. The mid-infrared absorber based on the annular array metasurface according to claim 1, It is characterized in that The material of the bottom metal layer is titanium.

3. The mid-infrared absorber based on the annular array metasurface according to claim 1, It is characterized in that The material of the dielectric layer is silicon.

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