SUPERCONDUCTING TUNNEL JUNCTION DETECTOR

PROBLEM TO BE SOLVED: To provide a superconducting tunnel junction detector capable of increasing the amount of phonons which a superconducting tunnel junction element (STJ element) absorbs and detecting a photon with a high sensitivity.SOLUTION: A terahertz wave is applied from an end face of a substrate 11, on which an STJ element 10 is not mounted. A lattice vibration (phonons) is generated inside the substrate 11 due to absorption of the terahertz wave. This group of phonons travels inside the substrate 11 and reaches a lower superconducting electrode 12 of the STJ element 10 to generate quasiparticles by decoupling a cooper pair in the electrode. An increase of a tunnel current due to increase of the quasiparticles is detected as a signal. A lens for collecting light 21 is mounted on an irradiating terahertz wave side of the substrate 11 so as to face the one STJ element 10 across the substrate 11. The terahertz wave is collected by the lens for collecting light 21 into the one STJ element 10, which improves photon collection efficiency.