Terahertz direct detectors based on superconducting hot electron bolometers with microwave injection

Terahertz (THz) direct detectors based on superconducting niobium nitride (NbN) hot electron bolometers (HEBs) with microwave (MW) injection have been studied. Compared to the thermal biasing method, the injected MW is used here to bias the HEB to the optimum point. MW can be expected to be used as the easy read out for the detecting array. The used NbN HEB has an excellent performance as heterodyne detector with the noise temperature of 403 K working at 4.2 K and 0.65 THz. As the result, the noise equivalent power (NEP) of 1.4 pW/Hz 1/2 and the response time of 64 ps have been obtained for the direct detectors with MW injection.