Diffusion-Cooled Superconducting Hot-Electron Bolometer Heterodyne Mixer at 660 and 800 GHz

Anders J. Skalare, William R. McGrath, B. Bumble +4 more

Anders J. Skalare, William R. McGrath, B. Bumble +4 more

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 /spl 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.>

Alexei D. Semenov, Heinz‐Wilhelm Hübers, Heiko Richter +4 more

Anders J. Skalare, William R. McGrath, B. Bumble +5 more

Heterodyne measurements have been made at 533 GHz using a novel superconducting hot-electron bolometer in a waveguide mixer. The bolometer is a 0.3 μm long niobium microbridge with a superconducting transition temperature of 5 K. The short length ensures that electron diffusion dominates over electron-phonon interactions as the electron cooling mechanism, which should allow heterodyne detection with intermediate frequencies (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 receiver noise temperature of 650 K DSB. The −3 dB rolloff in the if response occurs at 1.7 GHz.

Klaus Fiegle, D. Diehl, Karl Jacobs

We report on heterodyne mixing experiments between 630-820 GHz using a diffusion-cooled superconducting hot electron bolometer at intermediate frequencies from 1-2 GHz. The niobium bolometer which is cooled by diffusion of the hot electrons into a normal conductor has dimensions of 0.3 /spl mu/m/spl times/0.15 /spl mu/m and was fabricated at KOSMA with a two-step electron beam lithography process. The film thickness of the device is 30 nm with T/sub c/ of 6.1 K and /spl Delta/T/sub c/ of 0.7 K. The mixing experiments are performed with a tunerless waveguide mixer block previously used for very low-noise SIS receivers. At a physical temperature of 2.2 K, receiver noise temperatures at 666 GHz are 1500 K at 1.0 GHz intermediate frequency, increasing rapidly above 1.5 GHz. The dissipated local oscillator power is evaluated to be 65-90 nW.

Serguei Cherednichenko, P. Khosropanah, E. Kollberg +2 more