Plasmon-enhanced terahertz photodetection in graphene

Graphene is a promising material for high speed room-temperature terahertz photodetection. However, the limited absorption in monolayer graphene remains a key challenge. We present here a large area terahertz detector that utilizes a plasmonic resonance in sub-wavelength graphene micro-ribbons to increase the absorption efficiency, and exploits the hot-electron photothermoelectric effect for detection. Through Fourier transform infrared spectroscopy we show that by tailoring the orientation of the graphene ribbons with respect to an array of sub-wavelength bimetallic electrodes, the plasmonic resonance can be efficiently excited, with a gate-tunable resonance frequency in the terahertz range. Polarization-dependent photoresponse measurements show an enhanced photothermal voltage between the outermost electrodes due to the plasmonically enhanced absorption.