High-Switching Contrast Plasmonic Nanocavities for Terahertz Detection with Extremely High Efficiency

We present a photoconductive terahertz detector that uses a plasmonic nanocavity to provide very high detection sensitivities at record-low optical pump power levels. To achieve this high efficiency operation, the plasmonic nanocavity is designed to limit the transport time of the photogenerated carriers to a sub-picosecond time scale. By using this detector in a terahertz time-domain spectroscopy system, we demonstrate more than a 100 dB signal-to-noise over a 6 THz bandwidth at only 0.1 mW optical pump power level.