Abstract-Passive terahertz imaging detectors based on antenna-coupled high-electron-mobility transistors

Jiandong Sun, Yifan Zhu, Wei Feng, Qingfeng Ding, Hua Qin, Yunfei Sun, Zhipeng Zhang, Xiang Li, Jinfeng Zhang, Xinxing Li, Yang Shangguan, and Lin Jin

 (a) Scanning-electron micrograph of the detector with schematic measurement circuitry. (b) Zoom-in view of the central active region including the gate and the field-effect channel. (c, d) Backside and front-side views of the silicon hyperhemispherical lens with a detector chip assembled on the planar surface in a liquid nitrogen dewar with a TPX window.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-4-4911

Aiming at the requirement of passive terahertz imaging, we report a high-sensitivity terahertz detector based on an antenna-coupled AlGaN/GaN high-electron-mobility transistor (HEMT) at 77 K without using low-noise terahertz amplifier. The measured optical noise-equivalent power and the noise-equivalent temperature difference of the detector were about 0.3pW/Hz−−−√$0.3\mathrm{p}\mathrm{W}/\sqrt{\mathrm{H}\mathrm{z}}$ and 370 mK in a 200 ms integration time over a bandwidth of 0.7 − 0.9 THz, respectively. By using this detector, we demonstrated passive terahertz imaging of room-temperature objects with signal-to-noise ratio up to 13 dB. Further improvement in the sensitivity may allow passive terahertz imaging using AlGaN/GaN-HEMT at room temperature.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Hydrodynamic simulations of terahertz oscillation in double-layer graphene

Wei Feng

http://iopscience.iop.org/article/10.1088/1674-4926/39/12/122005/pdf

We have theoretically studied current self-oscillations in double-layer graphene n+nn+ diodes driven by dc bias with the help of a time-dependent hydrodynamic model. The current self-oscillation results from resonant tunneling in the double-layer graphene structure. A detailed investigation of the dependence of the current self-oscillations on the applied bias has been carried out. The frequencies of current self-oscillations are in the terahertz (THz) region. The double-layer graphene n+nn+ device studied here may be presented as a THz source at room temperature.

Abstract-Nonlinear dynamics in a terahertz-driven double-layer graphene diode

Wei Feng, Lijuan Shi,

http://iopscience.iop.org/article/10.1088/1674-4926/39/12/124012/pdf

By using the time-dependent hydrodynamic equations, we carry out a theoretical study of nonlinear dynamics in an n+nn+ double-layer graphene diode driven by terahertz radiation. A cooperative nonlinear oscillatory mode shows up due to the negative differential conductance effect. We use different chaos-detecting methods, such as the Poincaré bifurcation diagram and the first return map, to examine the transitions between the periodic and chaotic states. The double-layer graphene diode shows typical nonlinear dynamical behavior with the DC bias, AC amplitudes and the AC frequency as the control parameters.