A HETERODYNE RECEIVER AT 533 GHZ USING A DIFFUSION-COOLED SUPERCONDUCTING HOT-ELECTRON BOLOMETER MIXER

This paper describes heterodyne measurements at 533 GHz using a novel superconducting hot electron bolometer in a waveguide mixer block. The bolometer is a thin (10 nm) and narrow (0.1 mu m) strip of niobium with a length of less than half a micron and a critical temperature of approximately 5.5 K. The short length ensures that diffusion dominates over electron-phonon interaction as a cooling mechanism for the hot electrons, thus allowing heterodyne detection with intermediate frequencies of several GHz. A Y-factor response of 1.15 dB has been obtained at an intermediate frequency of 1.4 GHz with hot/cold load temperatures of approximately 295/77 K, indicating a receiver noise temperature around 650 K DSB. The IF response extends up to at least 2 GHz and possibly higher.