Terahertz superconducting hot-electron bolometer mixers

摘要

Hot-electron bolometer frequency down-converters (mixers) based on superconducting films have been found to offer record sensitivity for THz receivers to be used in radio astronomy. In this paper we focus on mixers using NbN phonon-cooled devices. We show that recent theoretical models predict a performance that agrees well with experiments. Important mixer properties such as conversion efficiency, noise (sensitivity), and their variation with the intermediate frequency are discussed in view of our physical understanding using both experiments and theory. We conclude that despite the excellent results obtained so far, further improvements are to be expected when technology has developed further and unnecessary shortcomings in the measurement set-up have been taken care of.