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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.

Cataloged from PDF version of article. Strong directional selectivity is theoretically predicted and experimentally validated at the microwave frequencies in the beaming regime for a single subwavelength slit in nonsymmetric metallic gratings with double-side corrugations. The operation regime can be realized at a fixed angle of incidence when the surface-plasmon assisted transmission is significant within a narrow range of observation angles, if illuminating one of the grating interfaces, and tends to vanish for all observation angles, if illuminating the opposite interface. The studied effect is connected with asymmetry (nonreciprocity) in the beaming that occurs if the surface plasmon properties are substantially different for the two interfaces being well isolated from each other. (c) 2011 American Institute of Physics.