Nonequilibrium photon-induced hotspot: A new mechanism for photodetection in ultrathin metallic films

Abstract

A new class of photodetectors is proposed, based on localized heating of an ultrathin metallic film due to absorption of individual photons. For a 1 eV photon, the transient temperature rise can be of order 10 K or greater in a nonequilibrium ‘‘hotspot’’ on the nm spatial scale and ps timescale. If current is flowing in a metallic film with a temperature-dependent resistance, such a hotspot can give rise to a voltage pulse. This can provide the basis for an ultrafast photodetector with spectral sensitivity, in contrast to a conventional bolometer. Prospects for practical realization of infrared photodetectors based on this mechanism are discussed.