Xiaoxia Zheng

Broadband and polarization-insensitive metamaterial absorber based on hybrid structures in the infrared region

Abstract In this work, a new type of metamaterial absorber is proposed in the infrared region. This structure consists of metal-dielectric-metal. But the difference is that a square groove in the dielectric has been dug, and replaced by a metal. The simulated results show that this structure can achieve a broadband absorption. And the absorption bandwidth can be realized from 60.5 to 115.5 THz when the absorption efficiency is larger than 90%. And this structure is polarization-insensitive for incident electromagnetic waves. In addition, the structure can also achieve better absorption effect for a large incident angle, especially for TM polarized wave. What is more, a remarkably enhanced bandwidth can be realized by using a metal to fill the square groove which is dug in the dielectric. To further explain the mechanism of high absorption, the distribution of the electromagnetic field and power loss density at the resonance frequencies are analysed. And these novel properties make the absorbers have many applications including sensor, cloaking, etc.

Ultra-broadband metamaterial absorber based on the structure of resistive films

Abstract This paper presents a three-dimensional structure of metamaterial absorber, and the unit of the absorber is composed of six different size resistive films which are placed on the metal plane ground. The simulated results show that the absorber can realize ultra-broadband absorption, which is from 38 to 142 GHz when the absorption is larger than 90%. And the relative absorption bandwidth can achieve 115.5%. In addition, the proposed metamaterial absorber is polarization-insensitive, which has the same absorption spectra for TE and TM polarization waves. And the absorber has large incident and polarization angles. In the end, the power loss density is analyzed. Through observing the distribution of power loss density, a polarization-controlled metamaterial absorber can be implemented if subtract the resistance film of the horizontal direction or the vertical direction subtracted. And the polarization-controlled metamaterial absorber also has ultra-broadband absorption effect. We believe that the absorber will have many potential applications.

Design of a broadband, wide-angle metamaterial absorber base on hybrid structure

Abstract In this paper, we presented and investigated a special metamaterial absorber to achieve broadband absorption. Firstly, we proposed a two-dimensional (2D) structure, which include a hybrid layer on the top, a dielectric layer in the middle, and a metal ground on the bottom. By the hybrid design on the top layer of the absorber, we achieved broadband absorption. The relative bandwidth is 22.57%. Furthermore, in order to improve the absorption bandwidth, we changed the absorber as a three-dimensional (3D) structure. The simulated results show that the absorber can be obtained a broadband absorption, the relative bandwidth up to 82.93%. Compared to the two-dimensional structure, it is clear that the three-dimensional structure has a better absorption. According to the effective medium theory, the relative impedance is calculated to explain the absorption mechanism. Finally, we believe it will have many potential applications in sensing, energy harvest and so on.

Broadband visible metamaterial absorber based on a three-dimensional structure

ABSTRACT In this paper, a broadband metamaterial absorber is successfully designed by a three-dimensional structure. And the three-dimensional absorber is just obtained by a two-dimensional structure which rotates 90°along x-axis. The simulated results show that the absorption of the three-dimensional metamaterial absorber is much better than the two-dimensional absorber. Moreover, the absorber is polarization-sensitive for the incident electromagnetic waves due to the asymmetry of the structure. Compared with the Y-polarization wave, the proposed absorber can realize broadband absorption with greater than 90% from 355.6 to 737.7 THz for X-polarized wave. Finally, based on the analysis of the electric field and surface current distributions, it can demonstrate that the localized surface plasmons and dipoles resonances will play an important role in the broadband absorption. And we believe that the metamaterial absorber will have many potential applications in emitter and energy harvesting.

Ultra-broadband reflective polarization converter using ring-chain metamaterial

In this work, a novel bi-layered metamaterial structure composed of a ring-chain structure and metal sheet-backed is proposed, which can realize ultra-broadband reflected polarization conversion in the near-infrared spectral region. Numerical results reveal that the structure possesses the ability to convert x-polarized and y-polarized waves to their orthogonal direction in frequency range from 109.5 to 338.8 THz, and the polarization conversion ratio can reach 99%. Based oncurrent density, the physical mechanism of polarization conversion is investigated at the resonant frequency. What is more, the resonant frequencies can be tunable with the change of the structure parameters. In addition, the polarization conversion of this structure is sensitive to the incident angle.

A broadband and polarization-insensitive metamaterial absorber

In this work, a broadband and polarization-insensitive absorber with split-ring resonator in the infrared region is proposed. The structure is composed of three layers, in which material of first layer is low-conductivity alloy. The simulated result reveals that the structure can realize a broadband absorption above 90% from 15 THz to 27 THz, which is better than other structures in the previous works. Based on the simulated results we can demonstrate that the magnitude of absorption is closely with that of material of the first layer. A remarkable enhance bandwidth can be realized by using the low-conductivity alloy, because the alloy can make more electromagnetic energy dissipated in it. Meanwhile, the overlapping of the high absorption rate in near frequency also contributes to increase the bandwidth. In order to explain the mechanism of high absorption, the surface current distribution and power loss at the resonance frequencies are investigated. Due to the symmetry of this structure, it is insensitive for the polarization. These novel properties can lead to a new possibilities and solution in many applications, such as communication system, polarization-insensitive devices and so on.

Ultrathin and broadband metamaterial absorber based on new four L structure in infrared and visible region

In this paper, we proposed a broadband and polarization-insensitive metamaterial absorber in infrared and visible region. Our structure composed of three layers, and the remarkable difference is that two materials (InSb and Tin) are used in the top layer simultaneously. The numerical results show that a broadband absorption above 90% from 88.4 to 110.9 THz can be achieved for either transverse electric or magnetic polarization waves due to the effect of using hybrid materials. Moreover, the metamaterial is ultra-thin, having total of 0.3 μm, i.e., λ/10 with respect to the center frequency of the high absorption bands. In addition, the mechanism of high absorption at resonances is discussed based on the surface current and power loss distributions. The power loss distributions between high and low frequency resonant point are distinct. Importantly, the proposed absorber also have a broadband absorption from 639.7 THz to 796.7 THz by adjusting the parameter of the structure and the idea of broadening absorption bandwidth supplies a useful way in THz, infrared, even in optical region. The new “four L” structure absorber has potential application in sensing, energy harvest, integrated photodetectors and so on.

Asymmetric transmission of both linearly and circularly polarized waves in multi-layered meta-surface

In this paper, we propose and demonstrate a multi-layered chiral structure consisting of a y-shape, a half-gammadion and an S-shape which possesses the property of asymmetric transmission for both linearly and circularly polarized waves in microwave frequency band. Numerical simulated results indicate that the chiral structure realizes a maximum asymmetric transmission of 0.88 and 0.31 for circularly and linearly polarized waves, respectively, which exhibit magnitude improvement over previous chiral metamaterials. Specifically, the maximum asymmetric transmitted coefficient of the designed structure is insensitivity to the incident angles at the resonance frequency. Additionally, we also study the influence of dielectric substrate thickness on the asymmetric transmission effect in detail.