LENGTH SCALING OF BANDWIDTH AND NOISE IN HOT-ELECTRON SUPERCONDUCTINGMIXERS

Mixing experiments have been performed at frequencies from 4 to 20 GHz on Nb thin-film superconducting hot-electron bolometers varying in le ngth from 0.08 to 3 mu m. The intermediate frequency (IF) bandwidth is found to vary as L(-2), with L the bridge length, for devices shorter than root 12 L(e-ph) approximate to 1 mu m, with L(e-ph) the electron -phonon length. The shortest device has an IF bandwidth greater than 6 GHz, the largest reported for a low-T-c superconducting bolometric mi xer. The conversion efficiencies range from -5 to -11 dB (single sideb and, SSB). For short bridges, the mixer noise temperature is found to be as low as 100 K (double sideband, DSB), with little length dependen ce. The local oscillator power required is small, approximate to 10 nW . Such mixers are very promising for low-noise THz heterodyne receiver s. (C) 1996 American Institute of Physics.