Yao Qijun

Terahertz Direct Detection Characteristics of a Superconducting NbN Bolometer

We report the terahertz direct detection characteristics of a spiral antenna coupled NbN superconducting hot-electron bolometer (HEB) at a bath temperature of 4.2K. Thermal conductance determined from resistance transition curves with different bias currents is found to be 3 x 10(-7) W/K. The device shows a read-out circuit limited noise equivalent power (NEP) of 4.5x10(-12) W/Hz(1/2) at 4.2K with a home-made transimpedance amplifier operating at room temperature.

Noise Behaviour of a THz Superconducting Hot-Electron Bolometer Mixer

A quasi-optical superconducting NbN hot-electron bolometer (HEB) mixer is measured in the frequency range of 0.5-2.5 THz for understanding of the frequency dependence of noise temperature of THz coherent detectors. It has been found that noise temperature increasing with frequency is mainly due to the coupling loss between the quasi-optical planar antenna and the superconducting HEB bridge when taking account of non-uniform distribution of high-frequency current. With the coupling loss corrected, the superconducting HEB mixer demonstrates a noise temperature nearly independent of frequency.