A high-responsivity and broadband photoconductive terahertz detector based on a plasmonic nanocavity

We present a photoconductive terahertz detector to be used in terahertz time-domain imaging and spectroscopy systems without utilizing a short-carrier lifetime semiconductor for the photoconductive active region. A plasmonic nanocavity is used to form the photoconductive active region of the detector to limit the transport time of the majority of the photo-generated carrier to a sub-picosecond order and eliminate the need for a short-carrier lifetime semiconductor. We demonstrate that the presented detector is capable of detecting terahertz pulses over a 0.1–4.5 THz frequency band with more than a 100 dB dynamic range under a 5 mW optical pump power, exhibiting a comparable performance with the state-of-the-art photoconductive terahertz detectors based on short-carrier lifetime substrates.