SUBMILLIMETER-WAVE DETECTION WITH SUPERCONDUCTING TUNNEL-DIODES

Superconductor-insulator-superronductor (SIS) diodes are the detector elements in the most sensitive heterodyne receivers available from 100 to 500 GHz. SIS mixers are the front end of radio astronomical systems around the world. SIS mixer technology is being extended to 1 THz and higher frequencies for eventual use on spaceborne astronomical experiments. This review presents a theoretical framework for understanding SIS submillimeter detection using an optical photodiode theory. Both gain and noise in the SIS mixer are described in the terms of mixing on a photodiode. The role of impedance matching in the proper design of an SIS mixer is described. A variety of methods for achieving good impedance match at submillimeter frequencies are presented. The state of the submillimeter SIS mixer art as practiced in a variety of laboratories is described and summarized