Abstract-Tunable terahertz band-stop filter based on self-gated graphene monolayers with antidot arrays

Wei Wang, Dongxiao Yang, Zhenhai Qian, Chuanshan Xu, Chang Wang,

https://www.sciencedirect.com/science/article/pii/S0030401818305066

An electrically tunable terahertz band-stop filter, which is composed of self-gated graphene monolayers with antidot arrays, is proposed and numerically investigated in this letter. Simulation results show that a pronounced resonance trough caused by graphene surface plasmons (0, 1) mode is obtained, which can be used to realize terahertz band-stop filtering efficiently. Center frequency of the resonance trough can be dynamically controlled over a broad frequency range from 6.6 to 8.6 terahertz through changing the voltage from 8.5 to 24.9 volt. Besides, the proposed filter is independent on the polarization state of incident terahertz wave as a result of its high azimuthal symmetry. The influences of structural parameters, substrate properties and misalignment of the two perforated graphene monolayers are also taken into account in further investigations for better understanding characteristics of the terahertz filter. Specifically, the proposed filter can be applied for refractive index sensing as well with a high sensitivity larger than 8.2 μ$\mathrm{}$m/RIU, which is potentially valuable for gas detection and so on.

Abstract-Surface plasmons based terahertz modulator consisting of silicon–air–metal–dielectric–metal layers

Wei Wang, Dongxiao Yang, Zhenhai Qian

https://www.sciencedirect.com/science/article/pii/S0030401817310192

An optically controlled modulator of the terahertz wave, which is composed of a metal–dielectric–metal structure etched with circular loop arrays on both the metal layers and a photoexcited silicon wafer separated by an air layer, is proposed. Simulation results based on experimentally measured complex permittivities predict that modification of complex permittivity of the silicon wafer through excitation laser leads to a significant tuning of transmission characteristics of the modulator, forming the modulation depths of 59.62% and 96.64% based on localized surface plasmon peak and propagating surface plasmon peak, respectively. The influences of the complex permittivity of the silicon wafer and the thicknesses of both the air layer and the silicon wafer are numerically studied for better understanding the modulation mechanism. This study proposes a feasible methodology to design an optically controlled terahertz modulator with large modulation depth, high speed and suitable insertion loss, which is useful for terahertz applications in the future.

Abstract-Terahertz modulation based on surface plasmon resonance by self-gated graphene

Zhenhai Qian, Dongxiao Yang, Wei Wang

https://www.sciencedirect.com/science/article/pii/S0030401817311604

We theoretically and numerically investigate the extraordinary optical transmission through a terahertz metamaterial composed of metallic ring aperture arrays. The physical mechanism of different transmission peaks is elucidated to be magnetic polaritons or propagation surface plasmons with the help of surface current and electromagnetic field distributions at respective resonance frequencies. Then, we propose a high performance terahertz modulator based on the unique PSP resonance and combined with the metallic ring aperture arrays and a self-gated parallel-plate graphene capacitor. Because, to date, few researches have exhibited gate-controlled graphene modulation in terahertz region with low insertion losses, high modulation depth and low control voltage at room temperature. Here, we propose a 96% amplitude modulation with 0.7 dB insertion losses and ∼$$5.5 V gate voltage. Besides, we further study the absorption spectra of the modulator. When the transmission of modulator is very low, a 91% absorption can be achieved for avoiding damaging the source devices.