阅读说明：本技术 一种宽频超材料吸波器的设计 (Design of broadband metamaterial wave absorber ) 是由 王红燕 胡丹 马永康 于 2020-06-30 设计创作，主要内容包括：本发明公开了一种宽频超材料吸波器的设计,属于太赫兹技术领域的吸波器件。该吸波器件为三维周期性结构,其结构组成从下至上依次为：金属层(1)、介质层(2)和结构化石墨烯层(3)。本发明通过有限频域差分方法计算模拟出石墨烯对太赫兹波的吸收频谱,对吸波器件结构进行优化,得到理想的宽带吸收效果。本发明结构简单、易于加工；仅通过单层结构化石墨烯材料便可实现吸收率在90％以上,带宽为0.63THz的吸波器件。(The invention discloses a design of a broadband metamaterial wave absorber, and belongs to wave absorbing devices in the technical field of terahertz. The wave absorbing device is of a three-dimensional periodic structure, and the structure composition of the wave absorbing device is from bottom to top in sequence: the graphene layer structure comprises a metal layer (1), a dielectric layer (2) and a structured graphene layer (3). According to the invention, the absorption spectrum of the graphene to the terahertz waves is calculated and simulated by a finite frequency domain difference method, and the structure of the wave absorption device is optimized to obtain an ideal broadband absorption effect. The invention has simple structure and easy processing; the wave absorbing device with the absorption rate of over 90 percent and the bandwidth of 0.63THz can be realized only by using the single-layer structured graphene material.)

1. The design of a broadband metamaterial wave absorber is characterized in that: the wave absorbing device is of a three-dimensional periodic structure, and the structure composition of the wave absorbing device is from bottom to top in sequence: the graphene layer structure comprises a metal layer (1), a dielectric layer (2) and a structured graphene layer (3).

2. The design of the broadband metamaterial wave absorber of claim 1, wherein: the metal layer (1) is made of gold, silver, copper or aluminum, and the thickness of the metal layer is 0.5 micrometer.

3. The design of the broadband metamaterial wave absorber of claim 1, wherein: the dielectric layer (2) is made of silicon dioxide and has the thickness of 31 microns.

4. The design of the broadband metamaterial wave absorber of claim 1, wherein: the structured graphene layer (3) is composed of four graphene shuttle-shaped sheets with the same shape.

5. The design of the broadband metamaterial wave absorber of claim 4, wherein: the four graphene shuttle-shaped sheets with the same shape are connected end to form a circular structure.

6. The design of the broadband metamaterial wave absorber of claim 1, wherein: the structured graphene layer (3) is of a single-layer atomic arrangement structure.

7. The design of the broadband metamaterial wave absorber of claim 1, wherein: the structured graphene layer (3) has a fermi level of 0.5eV and a relaxation time of 0.3 ps.

8. The design of the broadband metamaterial wave absorber of claim 1, wherein: the metal layer (1) is used as a mirror.

Technical Field

The invention relates to the technical field of terahertz, in particular to a design of a broadband metamaterial wave absorber. The wave absorber structure can realize the characteristics of broadband absorption, large-angle broadband absorption and insensitive polarization, and can be used in the fields of terahertz detection of terahertz wave bands, terahertz imaging, terahertz stealth and the like.

Background

The terahertz wave is generally an electromagnetic wave with a frequency within the range of 0.1-10 THz and is located between infrared wave and microwave. Due to the fact that the terahertz wave has many unique properties such as transient property, broadband property, low energy property, coherence and the like, the terahertz wave has important application prospects in the fields of basic research, industrial application, medicine, military, biology and communication. At present, a terahertz wave generation source and terahertz wave detection are recognized as two key problems restricting the development of terahertz technology. The absorption and energy capture of the terahertz wave are the basis for realizing terahertz detection and are the core problems of terahertz wave calibration, regulation, conversion and application. Therefore, the terahertz broadband absorption technology becomes one of the hot spots in the current terahertz technical field.

In recent years, the terahertz wave absorber based on the metamaterial has attracted attention because of having important application prospects in the fields of miniature bolometers, terahertz imaging, terahertz stealth technology, terahertz communication, food safety and the like. In many applications, terahertz broadband absorption is often required to prepare broadband terahertz functional devices such as sensors, modulators, microbolometers, broadband antireflection films and the like.

The invention constructs a broadband metamaterial terahertz wave absorber on the basis of graphene. The wave absorber prepared by the structure has the characteristics of high broadband wave absorption rate, large incident angle, insensitive polarization, thin thickness and the like.

Disclosure of Invention

In order to overcome the technical problems, the invention provides a design of a broadband metamaterial wave absorber, which achieves the aim of high absorption in a wider frequency range.

In order to achieve the purpose, the invention can be realized by the following technical scheme: the design of a broadband metamaterial wave absorber is characterized in that: the wave-absorbing device is a three-dimensional periodic structure, and the structure composition of the wave-absorbing device is from bottom to top in sequence: the graphene layer structure comprises a metal layer (1), a dielectric layer (2) and a structured graphene layer (3).

The metal layer (1) is made of gold, silver, copper or aluminum and has a thickness of 0.5 micron.

The dielectric layer (2) is made of silicon dioxide and has the thickness of 31 microns.

The structured graphene layer (3) is composed of four graphene shuttle-shaped sheets with the same shape.

The four graphene shuttle-shaped sheets with the same shape are connected end to form a circular structure.

The structured graphene layer (3) is of a single-layer atomic arrangement structure.

The structured graphene layer (3) has a fermi level of 0.5eV and a relaxation time of 0.3 ps.

The metal layer (1) is used as a mirror.

The invention has the beneficial effects that:

(1) the invention can realize the absorption of broadband terahertz waves, the absorption bandwidth is 0.63THz, and the absorption efficiency is higher than 90%.

(2) The invention has simple structure and generality, and can be used for absorbing electromagnetic waves of mid-infrared, far-infrared, microwave or other wave bands through scale conversion.

(3) The wave absorber has the advantages of simple and compact structure, perfect symmetry and easy realization, and can also enable the wave absorber to have polarization insensitivity.

Drawings

FIG. 1: the unit structure of the embodiment of the invention is schematically shown.

FIG. 2: the top view of the unit structure of the embodiment of the invention.

FIG. 3: the absorption spectrum of the wave absorber when different polarized waves are normally incident.

FIG. 4: and the absorption spectrum of the wave absorber when the horizontally polarized wave is obliquely incident.

FIG. 5: and the absorption spectrum of the wave absorber when the vertically polarized wave is obliquely incident.

The above pictures contain: p is 40 microns; t is t_m0.5 microns; t is t_d31 microns.

1: a metal; 2: silicon dioxide; 3: structured graphene.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

FIG. 1 and FIG. 2 are a schematic diagram and a top view, respectively, of a cell structure of an embodiment of the present invention, using a length and a width of p and a thickness of t_mAs the metal layer (1) of copper, with a thickness t_dThe silicon dioxide is used as a medium layer (2), the structured graphene layer (3) is composed of four graphene spindle-shaped sheets with completely the same shape, and the four graphene spindle-shaped sheets with completely the same shape are connected end to form a circular structure.

The working principle of the wave absorber structure can be explained by the following contents: in the present invention, copper with a depth greater than the skin depth is used as the metal layer, so that the incident light cannot be transmitted but can be reflected back, and therefore the formula of the absorption rate is a (ω) 1-R (ω). Due to the metallicity of graphene, the graphene layer can generate surface plasma like metal under the action of electromagnetic waves, and the structured graphene layer can generate electric resonance under the action of incident electromagnetic waves; the structured graphene layer is close enough (only 31 microns) to the metal layer that it couples strongly to the metal layer, creating an anti-parallel current that creates magnetic resonance. When the electric and magnetic resonance makes the dielectric constant and the magnetic conductivity equal, the impedance of the structure is matched with the impedance in the free space, and the reflectivity can be made to be zero. At the moment, a proper amount of loss is introduced into the structure, so that the radiation loss of the structure is equal to the intrinsic absorption rate, and the maximum electromagnetic wave absorption can be realized.

FIG. 3 is an absorption spectrum of a wave absorber at normal incidence of waves of different polarizations. Here, the chemical potential of graphene is set to 0.5eV and the relaxation time is set to 0.3 ps. The wave absorber structure has strong absorption property on incident terahertz waves, the bandwidth with the absorption rate of more than 90% reaches 0.63THz, the relative bandwidth is about 50%, the wave absorber is insensitive to the polarization mode, and the absorption spectra under horizontal polarization and vertical polarization are completely the same.

Fig. 4 and 5 are absorption spectra of the wave absorber when horizontally polarized waves and vertically polarized waves are obliquely incident, respectively, and the wave absorber can still achieve a bandwidth of 0.6THz with an absorption rate of more than 80% at an incident angle of 50 °.

In conclusion, the wave absorbing device structure has obvious design characteristics of absorption frequency band, absorption rate and different polarization oblique incidence wave absorbing performance, and can adapt to different application environments and performance requirements through the adjustment of the thickness of the medium layer and the parameters of the structured graphene layer; the wave absorber structure adopts three raw materials of graphene, copper and silicon dioxide, which are low in cost and easy to obtain, has good economic affordability, and can be widely applied to the fields of broadband stealth materials, wave-absorbing skins, wave-absorbing devices and the like of terahertz wave bands.