Abstract
This study reviews recent advances in room-temperature coherent amplification of terahertz (THz) radiation in graphene, electrically driven by a dry cell battery. Our study explores THz light–plasmon coupling, light absorption, and amplification using a current-driven graphene-based system because of its excellent room temperature electrical and optical properties. An efficient method to exploit graphene Dirac plasmons (GDPs) for light generation and amplification is introduced. This approach is based on current-driven excitation of the GDPs in a dual-grating-gate high-mobility graphene channel field-effect transistor (DGG-GFET) structure. The temporal response of the DGG-GFETs to the polarization-managed incident THz pulsation is experimentally observed by using THz time-domain spectroscopy. Their Fourier spectra of the transmitted temporal waveform through the GDPs reveals the device functions 1) resonant absorption at low drain bias voltages below the first threshold level, 2) perfect transparency between the first and the second threshold drain bias levels, and 3) resonant amplification beyond the second threshold drain bias voltage. The maximal gain of 9% is obtained by a monolayer graphene at room temperatures, which is four times higher than the quantum limit that is given when THz photons directly interact with electrons. The results pave the way toward tunable graphene plasmonic THz amplifiers.
Highlights
Graphene is promised to a wealth of interesting applications, and graphene plasmonics is emerging as one of the most viable paths for bringing those applications into reality [1, 2]
Tunable Graphene Plasmonic THz Amplifiers based on the Smith–Purcell effect [28], which face severe difficulties to operate beyond the millimeter-wave region [29]
We investigate dc current-driven plasmonic amplification in high-mobility graphene-channel transistor graphene channel field-effect transistor (GFET) structures that combine the advantage of an efficient tunable absorber, emitter, and amplifier at room temperatures
Summary
Graphene is promised to a wealth of interesting applications, and graphene plasmonics is emerging as one of the most viable paths for bringing those applications into reality [1, 2]. Graphene is currently taking off as one of the most vibrant and promising alternatives in the race for new plasmonic materials [7], especially in the mid to far-infrared (THz) regions [8,9,10,11,12,13,14]. The main idea has been to exploit the radiative decay of grating-coupled 2D plasmons for the realization of compact tunable solid-state far-infrared devices [15,16,17,18,19,20,21,22,23,24,25,26,27] and develop new alternatives to the vacuum devices, such as traveling wave and backward wave tubes. Tunable Graphene Plasmonic THz Amplifiers based on the Smith–Purcell effect [28], which face severe difficulties to operate beyond the millimeter-wave region [29]. The intensity of radiation reported experimentally so far is too small [16, 24,25,26], and the plasmon resonances are too broad and not tunable enough [27] to be promising for device applications
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