Abstract-Dynamically tunable polarization-independent terahertz absorber based on bulk Dirac semimetals

Ming Chen, Chen Chen, Shijie Deng, Houquan Liu, Chuanxin Teng, Yu Cheng, Hongyan Yang, Ronghui Xu, Hongchang Deng, and Libo Yuan

Fig. 1. Schematic of the 3×$\times$3 unit structure of the proposed absorber which is composed of a patterned Dirac semimetal film, the dielectric layer and a metal reflector. The incident electric field is along the 𝑥$x$-axis and the magnetic field is along the 𝑦$y$-axis.

https://www.osapublishing.org/osac/abstract.cfm?uri=osac-2-8-2477

In this paper, we propose a tunable and polarization-independent absorber based on a bulk Dirac semimetal (BDS) metasurface at terahertz frequencies with a high absorption. The numerical results show that the full width at half maximum is △𝑓=9.1×10−2$△f=9.1\times {10}^{-2}$ THz. The absorption is maintained at above 95% when the Fermi level is in the range from 65 meV to 85 meV and the resonance frequency is in the range from 2.46 THz to 3.16 THz. For both polarizations, the absorption peak is maintained at above 80% for incident angles up to 60∘${60}^{\circ }$. Based on our method, various BDS-based tunable absorbers can be designed for terahertz, infrared, and visible frequencies. This significantly enhances the usefulness of these absorbers in a wide range of applications such as sensing systems and optoelectronic devices.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Wideband circular polarization converter based on graphene metasurface at terahertz frequencies

Chongyun Wang,  Ming Chen,  Houquan Liu,  Chuanxin Teng, Hongchang Deng,  Libo Yuan

https://www.spiedigitallibrary.org/journals/Optical-Engineering/volume-58/issue-4/043106/Wideband-circular-polarization-converter-based-on-graphene-metasurface-at-terahertz/10.1117/1.OE.58.4.043106.short?SSO=1

Linear-to-circular polarization converters are widely used in optical and microwave systems, but the polarization devices of traditional materials are untunable, and devices made of graphene materials can overcome this disadvantage. A circular polarization converter based on graphene metasurface is designed, whose properties are tunable over a broad range at terahertz frequencies. With appropriate structural parameters, simulations show that the axial ratio of reflected electromagnetic wave of the proposed device is lower than 3 dB in the frequency band of 2.25 to 2.475 THz, which means the linearly incident polarization can be converted to the circular polarization wave. The proposed design can also work when the electromagnetic wave is oblique incidence up to 40 deg with a high polarization conversion ratio. Moreover, the operating frequency band can be arbitrarily adjusted by applying a bias voltage.

© 2019 Society of Photo-Optical Instrumentation Engineers (SPIE) 0091-3286/2019/$25.00 © 2019 SPIE