Abstract-Dual-regulated broadband terahertz absorber based on vanadium dioxide and graphene

 

Chunyu Zhang, Heng Zhang, Fang Ling, and Bin Zhang

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-60-16-4835

A tunable broadband terahertz (THz) absorber based on vanadium dioxide (VO2${\mathrm{V}\mathrm{O}}_2$) and graphene is proposed. The absorber, consisting of the VO2${\mathrm{V}\mathrm{O}}_2$ square loop, polymethacrylimide (PMI) dielectric layer, and a layer of unpatterned graphene, can achieve absorption over 90% from 1.04 THz to 5.51 THz and relative bandwidth of up to 136.5% under normal incidence. Its absorption bandwidth and absorption peak can be adjusted by changing the conductivity of VO2${\mathrm{V}\mathrm{O}}_2$ or the chemical potential of graphene. The physical mechanism of the absorber is analyzed in detail by the use of the impedance matching theory and the electric field distributions of the VO2${\mathrm{V}\mathrm{O}}_2$ layer and graphene layer. The proposed absorber, with polarization insensitivity and incidence angle of 30° for both TE and TM polarizations, may have potential applications in tunable sensors, modulators, and imaging.

© 2021 Optical Society of America

Abstract-A broadband tunable terahertz negative refractive index metamaterial

Fang Ling, Zheqiang Zhong, Renshuai Huang,  Bin Zhang

https://www.nature.com/articles/s41598-018-28221-3

A strategy to greatly broaden negative refractive index (NRI) band, reduce loss and ease bi-anisotropy of NRI metamaterials (MMs) has been proposed at terahertz frequencies. Due to the symmetric structure of the MM, the transmission and refractive index are independent to polarizations of incident radiations, and a broadband NRI is obtainable for the range of the incident angle from 0° to 26°. In addition, THz MMs’ properties such as transmission, phase and negative refraction exhibit a real-time response by controlling the temperature. The results indicate that the maximum bands of the negative and double-negative refraction are 1.66 THz and 1.37 THz for the temperature of 40 °C and 63 °C, respectively. The figure of merit of the MMs exceeds 10 (that is, low loss) as the frequency increases from 2.44 THz to 2.56 THz in the working temperature range, and the maximum figure of merit is 83.77 at 2.01 THz where the refractive index is −2.81 for a given temperature of 40 °C. Furthermore, the negative refraction of the MMs at the low loss band is verified by the classical method of the wedge, and the symmetric slab waveguide based on the proposed MM has many unique properties.

Abstract-Study on thermally control terahertz narrow bandpass filter

Fang Ling; Renshuai Huang; Qinglong Meng; Weili Li; Bin Zhang;

In general, the terahertz metamaterial filter based on the complementary structure mainly has the fixed resonant frequency and asymmetric resonant frequency edges. In this paper, a thermally control terahertz narrow bandpass filter consisting of a periodic array of complementary wires embedded with thermosensitive semiconductor indium antimonide (InSb) has been proposed. Due to the structure of the filter is relatively simple, it can be more easily fabricated by lithograph technology compared with traditional terahertz metamaterial filter structure. Furthermore, its performance has also been analyzed based on the effective medium theory and the Drude model. The results show that the resonant frequency shifts from 1.16THz to 2.11THz with the increasing of the temperature from 160K to 360K, and the blueshift of resonance frequency as large as 81% can be implemented. Meanwhile, the reflectivity at the resonant frequency almost tends to be zero and the transmissivity spectrum at the resonant frequency exhibits sharp and symmetric edges. The filter can be applied to THz imaging system, and can effectively improve the imaging quality as a result of well characteristics of dynamic tuned filer and relatively simple structure.

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