Hot Electron Superconductive Mixers

H. Ekström, Boris S. Karasik, E. Kollberg +1 more

GuoAo Xie, Ruixuan Tang, Zhenlin Luo +6 more

Response time of a Superconducting Hot Electron Bolometer (HEB) mixers is a critical parameter, and significantly affects the intermediate frequency (IF) gain bandwidth. In this study, we investigated the effects of temperature and bias voltage on the response time. Response time of superconducting niobium nitride (NbN) HEB mixers were measured by using the pumpprobe technique at temperatures of 5 K, 7 K, and 9 K with different bias voltages. The measured response time ranged from 50 to 80 ps and decreased with increasing temperature and bias voltage. This approach provides a more comprehensive understanding of the thermal transport mechanisms in superconducting HEB mixers, which can ultimately lead to improved performance and properties of the HEB mixers.

Dag Winkler

Wen Zhang, Ning Li, Ling Jiang +6 more

It is known that the increase of bath temperature results in the decrease of critical current of superconducting hot-electron bolometer (HEB) mixers owing to the depression of superconductivity, thus leading to the degradation of the mixer's sensitivity. Here we report our study on the effect of bath temperature on the heterodyne mixing performance of quasi-optical superconducting NbN HEB mixers incorporated with a two-arm log-spiral antenna. The correlation between the bath temperature, critical current, LO power requirement and noise temperature is investigated at 0.5 THz. Furthermore, the heterodyne mixing performance of quasi-optical superconducting NbN HEB mixers is examined while there is an optical-axis displacement between the center of the extended hemispherical silicon lens and the superconducting NbN HEB device, which is placed on the back of the lens. Detailed experimental results and analysis are presented.

E. Kollberg

William R. McGrath, Boris S. Karasik, Anders J. Skalare +3 more

Superconductive hot-electron bolometer (HEB) mixers have been built and tested in the frequency range from 1.1 THz to 2.5 THz. The mixer device employs diffusion as a cooling mechanism for hot electrons. The double sideband receiver noise temperature was measured to be approximately equals 2750 K at 2.5 K at 2.5 THz; and mixer IF bandwidths as high as 9 GHz are achieved for 0.1 micrometers long devices. The local oscillator power dissipated in the HEB microbridge was in the range 20- 100 nW. Further reductions in LO power and mixer noise can be potentially achieved by using Al microbridges. The advantages and parameters of such devices are evaluated. A distributed-temperature model has been developed to properly describe the operation of the diffusion-cooled HEB mixer. The HEB mixer is a primary candidate for ground based, airborne and spaceborne heterodyne instruments at THz frequencies.