CN113690632A

CN113690632A - Broadband polarization insensitive metamaterial wave absorber

Info

Publication number: CN113690632A
Application number: CN202111000888.5A
Authority: CN
Inventors: 王云姬; 邱亚涛; 倪波
Original assignee: Jinling Institute of Technology
Current assignee: Jinling Institute of Technology
Priority date: 2021-08-30
Filing date: 2021-08-30
Publication date: 2021-11-23

Abstract

The invention provides a broadband polarization insensitive metamaterial wave absorber which is characterized in that the wave absorber is of a periodic structure, each wave absorber is composed of M multiplied by N periodic units, the periodic unit structure is square, the unit side length is 500nm, and the wave absorber of each periodic unit comprises: the resonant structure, the metal tungsten, the dielectric layer and the metal bottom layer are sequentially arranged from top to bottom; the resonant structure includes: a symmetrical cross structure and a cylinder; the cross structure is symmetrical and is positioned in the middle of the metal tungsten; the four cylinders are positioned in the center of the blank area of the cross structure. The invention aims to provide a metamaterial wave absorber insensitive to broadband polarization, and the metamaterial structure is constructed by selecting conventional materials Ni (nickel) and W (tungsten) to realize broadband absorption of optical wave bands.

Description

Broadband polarization insensitive metamaterial wave absorber

Technical Field

The invention belongs to the technical field of optical broadband metamaterial wave absorbers, and particularly relates to a metamaterial wave absorber insensitive to broadband polarization.

Background

The metamaterial is an artificial composite material which is formed by periodically arranging metal and dielectric and has electromagnetic properties which are not usually existed in natural materials.

Since the concept of metamaterial absorbers proposed by land (see documents n.i. land, s.sajuyigbe, j.j.mock, d.r.smith, w.j.padilla, s.sajuyigbe, and d.j.mock, Perfect metallic absorber, phys.rev.lett.100(20),207402(2008)), the metamaterial absorbers have led to extensive research due to their application prospects in the fields of electromagnetic protection, microwave darkrooms, mobile communication and solar cells.

The metal Ni (nickel) is adopted as the surface metal of the metamaterial wave absorber, the wave absorbing range of the metamaterial wave absorber can cover visible light (400nm-760nm), and the metamaterial wave absorber is researched by many people. This is due to the intrinsic properties of metallic Ni. Further broadening of the absorption band of nickel-based metamaterial absorbers requires further optimization of the metamaterial structure.

Disclosure of Invention

Aiming at the problems, the invention aims to provide a metamaterial wave absorber insensitive to broadband polarization, and the metamaterial structure is constructed by selecting conventional materials Ni (nickel) and W (tungsten) to realize broadband absorption of optical wave bands.

The invention provides a broadband polarization insensitive metamaterial wave absorber which is of a periodic structure, each wave absorber is composed of M multiplied by N periodic units, the shape of the periodic unit structure is square, the unit side length is 500nm, and the wave absorber of each periodic unit comprises: the resonant structure, the metal tungsten, the dielectric layer and the metal bottom layer are sequentially arranged from top to bottom;

the resonant structure includes: a symmetrical cross structure and a cylinder;

the cross structure is symmetrical and is positioned in the middle of the metal tungsten;

the four cylinders are positioned in the center of the blank area of the cross structure.

As a further improvement of the invention, the resonance structure is made of metallic nickel Ni, and the thickness of the resonance structure is 170 nm.

As a further improvement of the invention, the thickness of the metal tungsten is 20nm, the dielectric layer is formed by SiO2, the thickness of the dielectric layer is 80nm, the metal bottom layer is formed by metal nickel Ni, the thickness of the metal bottom layer is 120nm, the thickness of the Ni metal layer at the bottom layer is larger than the skin depth of infrared band electromagnetic waves in the metal layer at the bottom layer, and the length of the metal tungsten, the dielectric layer and the metal bottom layer is 400nm, and the width of the metal tungsten, the dielectric layer and the metal bottom layer is 100 nm.

As a further improvement of the invention, the cylinder radius is 50 nm.

As a further improvement of the invention, the periodic unit of the wave absorbing body of the metamaterial comprises a four-layer structure: a metal layer composed of Ni (nickel) at the bottom layer, a dielectric layer composed of SiO2 and positioned right above the metal layer at the bottom layer, a metal thin layer composed of W (tungsten) and positioned above the dielectric layer, and a surface metal pattern layer composed of Ni at the top;

as a further improvement of the invention, the wave absorber of the metamaterial is scanned in a wave band of 400nm to 1500nm to obtain the transmissivity and reflectivity of the material, so that the absorption rate of the wave absorber to electromagnetic waves is calculated;

as a further improvement of the invention, the structural parameters of the metamaterial wave absorber are changed, so that the absorption frequency of the structure can be changed.

Has the advantages that:

according to the invention, the wave absorbing material and the artificial microstructure are utilized to form the three-dimensional metamaterial wave absorber, so that the absorption rate of a broadband of more than 90% can be realized at 560 nm-1430 nm, and the average wave absorbing effect of more than 96.07% can be realized in the wave band. In addition, the three-dimensional metamaterial wave absorber is insensitive to polarization.

Drawings

FIG. 1 is a top view of a three-dimensional metamaterial absorber, wherein coordinate axes represent directions of x, y and z axes in a structure;

FIG. 2 is a front view of a three-dimensional metamaterial wave absorber;

FIG. 3 shows the reflectance R and the absorbance A of a horizontal polarized wave with a wave band of 400nm to 1500nm by the metamaterial wave absorber of the invention, and the structure respectively achieves 99.16% and 98.30% of absorbance at 654nm and 961 nm;

FIG. 4 shows the absorption of the metamaterial absorber when incident vertically polarized waves.

Detailed Description

The invention is described in further detail below with reference to the following detailed description and accompanying drawings:

the invention provides a metamaterial wave absorber insensitive to broadband polarization, which can realize a good broadband absorption effect and has the polarization insensitivity.

As shown in fig. 1 and fig. 2, the metamaterial wave absorber is a periodic structure, each periodic unit structure of the wave absorber is square, and the unit side length is 500 nm; each wave absorber periodic unit comprises four layers of structures: the bottom metal layer 5 is 120nm thick and larger than the skin depth of the infrared band electromagnetic wave in the bottom metal layer; the dielectric layer 4 is positioned right above the bottom metal layer, and the thickness of the dielectric layer is 80 nm; the metal thin layer is positioned right above the dielectric layer 2, and the thickness of the metal thin layer is 20 nm; and the resonant structure is positioned right above the metal thin layer and has the thickness of 170 nm.

As shown in the figure, the surface layer of the metamaterial wave absorber is a resonance structure and consists of a cross structure 1 and four cylinders 2; the cross is of a symmetrical structure, is positioned in the center of the thin metal layer, and is 400nm long and 100nm wide; the four cylinders are positioned in the center of the blank of the cross structure and have the radius of 50 nm.

In practical application, the metamaterial wave absorber is of a four-layer structure, and the metal layer 5 and the

resonant structures

1 and 2 are made of metal nickel. In practical application, the metal thin layer 3 is metal tungsten.

In practical applications, the dielectric layer 4 is silicon dioxide.

The absorption of electromagnetic waves by the absorber can be expressed by the following formula: a ω ═ 1-T ω -R ω.

Where a ω represents absorption, R ω represents reflection, and T ω represents transmission. When the bottom layer of the wave absorber is metallic nickel, T omega can be ignored. The above formula can thus be expressed as: a ω 1-R ω.

According to the above formula, the absorption rate of the absorber can be obtained.

The transmittance and the reflectivity of the material are obtained by scanning the metamaterial wave absorber in a wave band of 400nm to 1500nm, and the absorption spectrum line is obtained by calculation.

The simulation result of the structure irradiated by the horizontal polarized wave is shown in fig. 3. Absorptance and Reflectance in the figure represent absorbance and Reflectance, respectively. The wave absorber reaches 99.16% at 654nm, 98.30% at 961nm, more than 90% absorption rate at 560 nm-1430 nm, and 96.07% average absorption rate in the band; in this case, the designed three-dimensional metamaterial wave absorber has a dual-band perfect absorption effect.

The simulation result of the structure irradiated by the vertical polarized wave is shown in fig. 4. The absorptance in fig. 4 is the same as that in fig. 3, indicating that the three-dimensional metamaterial absorber has polarization insensitivity.

In summary, by means of the technical scheme of the invention, the three-dimensional metamaterial wave absorber composed of the wave absorbing material and the artificial microstructure is utilized, so that a good broadband absorption effect and polarization insensitivity are realized.

The above description is only one of the preferred embodiments of the present invention, and is not intended to limit the present invention in any way, but any modifications or equivalent variations made in accordance with the technical spirit of the present invention are within the scope of the present invention as claimed.

Claims

1. The broadband polarization insensitive metamaterial wave absorber is characterized in that the wave absorber is of a periodic structure, each wave absorber is composed of M multiplied by N periodic units, the periodic unit structure is square, and the wave absorber of each periodic unit comprises: the resonant structure, the metal tungsten (3), the dielectric layer (4) and the metal bottom layer (5) are sequentially arranged from top to bottom;

the resonant structure includes: a symmetrical cross structure (1) and a cylinder (2);

the cross structure (1) is symmetrical and is positioned in the middle of the metal tungsten (3);

four columns (2) are positioned at the center of the blank area of the cross structure.

2. The broadband polarization insensitive metamaterial wave absorber of claim 1, wherein: the resonant structure is composed of metallic nickel Ni.

3. The broadband polarization insensitive metamaterial wave absorber of claim 1, wherein: the thickness of the resonant structure is 170 nm.

4. The broadband polarization insensitive metamaterial wave absorber of claim 1, wherein: the thickness of the metal tungsten (3) is 20 nm.

5. The broadband polarization insensitive metamaterial wave absorber of claim 1, wherein: the dielectric layer (4) is made of SiO₂And (4) forming.

6. The broadband polarization insensitive metamaterial wave absorber of claim 1, wherein: the thickness of the dielectric layer (4) is 80 nm.

7. The broadband polarization insensitive metamaterial wave absorber of claim 1, wherein: the metal bottom layer (5) is made of metal nickel Ni.

8. The broadband polarization insensitive metamaterial wave absorber of claim 1, wherein: the thickness of the metal bottom layer (5) is 120 nm.

9. The broadband polarization insensitive metamaterial wave absorber of claim 1, wherein: the metal tungsten (3), the dielectric layer (4) and the metal bottom layer (5) are 400nm long and 100nm wide.

10. The broadband polarization insensitive metamaterial wave absorber of claim 1, wherein: the radius of the cylinder (2) is 50 nm.