PHOTODETECTOR

摘要

A photodetector 1A comprises an optical element 10, having a structure including first regions and second regions periodically arranged with respect to the first regions along a plane perpendicular to a predetermined direction, for generating an electric field component in the predetermined direction when light is incident thereon along the predetermined direction; and a semiconductor multilayer body 4 having a quantum cascade structure, arranged on the other side opposite from one side in the predetermined direction with respect to the optical element, for producing a current according to the electric field component in the predetermined direction generated by the optical element 10; while the quantum cascade structure includes an active region 4b having a first upper quantum level and a second upper quantum level lower than the first upper quantum level, and an injector region 4c for transporting an electron excited by the active region 4b.