LARGE BANDWIDTH AND LOW-NOISE IN A DIFFUSION-COOLED HOT-ELECTRON BOLOMETER MIXER

Heterodyne measurements have been made at 533 GHz using a novel superc onducting hot-electron bolometer in a waveguide mixer. The bolometer i s a 0.3 mu m long niobium microbridge with a superconducting transitio n temperature of 5 K. The short length ensures that electron diffusion dominates over electron-phonon interactions as the electron cooling m echanism, which should allow heterodyne detection with intermediate fr equencies (if) of several GHz. A Y-factor response of 1.15 dB has been obtained at an if of 1.4 GHz with 77 and 295 K loads, indicating a re ceiver noise temperature of 650 K DSB. The -3 dB rolloff in the if res ponse occurs at 1.7 GHz. (C) 1996 American Institute of Physics.