Abstract-Dual-band ultrasensitive terahertz sensor based on tunable graphene metamaterial absorber

 

Tao Chen, Weijie Jiang, Xianhua Yin, 

https://www.sciencedirect.com/science/article/abs/pii/S0749603621000963

In this paper, we propose a dual-band tunable absorber with a graphene-dielectric-metal structure as a sensor in the terahertz (THz) region. The finite element method (FEM) based on the CST microwave studio software is used in modeling and numerical analysis. Strong interaction between graphene surface plasmon resonance (SPR) and the absorber gives rise to two ultra-narrow perfect absorption peaks, and the position of the resonance frequencies can be adjusted by tuning the chemical potential of graphene in a wide range. In addition, the high symmetry of the absorber brings polarization and angle insensitivity, in which an absorption rate of over 90% can be obtained when the oblique incident angle is close to 80° in the transverse magnetic (TM) mode. For refractive index sensing, the simulation results show that the proposed structure achieves the maximum sensitivity, Q factor, and figure-of-merit (FOM) of 2.475 THz per refractive index unit (THz/RIU), 216.29, and 76.89 RIU−1, respectively. Therefore, we believe that the proposed sensor with such high performance has a promising application for biomedical diagnosis and environmental monitoring.

Abstract-Experimental and theoretical investigations of tartaric acid isomers by terahertz spectroscopy and density functional theory

Tao Chen, Qin Zhang, Zhi Li, Xianhua Yin, Fangrong Hu,

https://www.sciencedirect.com/science/article/pii/S1386142518306334

The terahertz (THz) absorption spectra of l-, d-, and dl-tartaric acid have been measured in the frequency range from 0.2 to 2.0 THz by terahertz time-domain spectroscopy (THz-TDS). The characteristic absorption peaks of these three tartaric acid isomers were obtained, which showed remarkable difference between enantiomers (l- and d-tartaric acid) and the racemic compound (dl-tartaric acid) in their peak frequencies. In parallel with the experimental study, theoretical calculations on isolated-molecule and unit cell of tartaric acids using density functional theory (DFT) were also performed for simulating the experimental THz spectrum features, which were in good agreement with the experimental data. Results demonstrate that THz-TDS can distinguish the tiny diversity between tartaric acid chiral isomers and its racemic compound, and provided an effective method for molecular identification in biological and biomedical engineering.

Abstract-Intensity modulation of a terahertz bandpass filter: utilizing image currents induced on MEMS reconfigurable metamaterials

Fangrong Hu, Yixing Fan, Xiaowen Zhang, Wenying Jiang, Yuanzhi Chen, Peng Li, Xianhua Yin, and Wentao Zhang

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-43-1-17&origin=search

We experimentally demonstrated a tunable terahertz bandpass filter based on microelectromechanical systems (MEMS) reconfigurable metamaterials. The unit cell of the filter consists of two split-ring resonators (SRRs) and a movable bar. Initially, the movable bar situates at the center of the unit cell, and the filter has two passbands whose central frequencies locate at 0.65 and 0.96 THz. The intensity of the two passbands can be actively modulated by the movable bar, and a maximum modulation depth of 96% is achieved at 0.96 THz. The mechanism of tunability is investigated using the finite-integration time-domain method. The result shows that the image currents induced on the movable bar are opposite the resonance currents induced on the SRRs and, thus, weaken the oscillating intensity of the resonance currents. This scheme paves the way to dynamically control and switch the terahertz wave at some constant frequencies utilizing induced image currents.

© 2017 Optical Society of America