Terahertz detector using a Nb-based superconducting tunnel junction

We have developed a terahertz (THz) radiation detector using a Nb-based superconducting tunnel junction (STJ). The STJ was fabricated on a stoichiometric LiNbO/sub 3/ substrate. The incident THz photons absorbed by the substrate generate THz phonons, and a substantial amount of the phonons are detected by the STJ. The detector is expected to be sensitive to a wideband THz/far-infrared radiation above the energy gap of the Nb superconductor. We radiated monochromatic nanosecond THz pulses with the repetition rate of 49 Hz, and detected the corresponding periodic signals for the 1.1-1.9 THz radiation.