Abstract-Room temperature amplification of terahertz radiation by grating-gate graphene structures

Stephane Boubanga-Tombet, Wojciech Knap, Deepika Yadav, Akira Satou, Dmytro B. But, Vyacheslav V. Popov, Ilya V. Gorbenko, Valentin Kachorovskii, and Taiichi Otsuji

https://journals.aps.org/prx/accepted/52079K1dC0014a02342729a68f281fe27fbfc8908

We study terahertz (THz) radiation transmission through grating-gate graphene based nanostructures. We report on room temperature THz radiation amplification stimulated by current-driven plasmon excitation. Specifically, with increase of the dc current under periodic charge density modulation, we observe a strong red shift of the resonant THz plasmon absorption, followed by a window of complete transparency to incoming radiation, and subsequent amplification and blue shift of the resonant plasmon frequency. Our results are, to the best of our knowledge, the first experimental observation of energy transfer from dc current to plasmons leading to THz amplification. Additionally, we present a simple model offering phenomenological description of the observed THz amplification. This model shows that in the presence of dc current the radiation-induced correction to dissipation is sensitive to the phase shift between oscillations of carrier density and drift velocity. And with increasing current, the dissipation becomes negative, leading to amplification. The experimental results of this work, as all obtained at room temperature, pave the way towards the new 2D plasmons based, voltage tuneable THz radiation amplifiers.