Abstract-Tight-Binding Terahertz Plasmons in Chemical-Vapor-Deposited Graphene

Andrey Bylinkin, Elena Titova, Vitaly Mikheev, Elena Zhukova, Sergey Zhukov, Mikhail Belyanchikov, Mikhail Kashchenko, Andrew Miakonkikh, and Dmitry Svintsov

https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.054017

Transistor structures comprising graphene and subwavelength metal gratings hold great promise for plasmon-enhanced terahertz detection. Despite considerable theoretical effort, little experimental evidence for terahertz plasmons in such structures has been found so far. Here we report an experimental study of plasmons in graphene-insulator-grating structures using Fourier-transform spectroscopy in the 5–10-THz range. The plasmon resonance is clearly visible above the Drude absorption background even in chemical-vapor-deposited graphene with low carrier mobility of approximately ${10}^3$ ${\mathrm{cm}}^2/$V s. We show that the plasmon lifetime exceeds the transport relaxation time extracted from dc mobility, and argue that the former is weakly sensitive to scattering by grain boundaries and macroscopic defects inherent in chemical-vapor-deposited samples. We find that a grating coupler close to graphene strongly modifies the plasmon spectrum, which is determined by metal stripe width but not by grating period. We present a simple theory of grating-coupled two-dimensional plasmons, akin to the tight-binding theory of electrons in solids, that reproduces the observed resonant frequencies without fitting parameters. Our results demonstrate the prospect of large-area commercially available graphene for resonant terahertz detectors.

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Abstract-Ultra-compact injection terahertz laser using the resonant inter-layer radiative transitions in multi-graphene-layer structure

Alexander A. Dubinov, Andrey Bylinkin, Vladimir Ya. Aleshkin, Victor Ryzhii, Taiichi Otsuji, Dmitry Svintsov

(Submitted on 29 Nov 2016)

https://arxiv.org/abs/1611.09523

The optimization of laser resonators represents a crucial issue for the design of terahertz semiconductor lasers with high gain and low absorption loss. In this paper, we put forward and optimize the surface plasmonic metal waveguide geometry for the recently proposed terahertz injection laser based on resonant radiative transitions between tunnel-coupled grapheme layers. We find an optimal number of active graphene layer pairs corresponding to the maximum net modal gain. The maximum gain increases with frequency and can be as large as ~ 500 cm-1 at 8 THz, while the threshold length of laser resonator can be as small as ~ 50 mkm. Our findings substantiate the possibility of ultra-compact voltage-tunable graphene-based lasers operating at room temperature.