Terahertz (THz) Direct Detectors based on Superconducting HEBs with Thermal, Microwave and THz Biasing

Terahertz (THz) direct detectors based on superconducting niobium nitride (NbN) hot electron bolometers (HEBs) with thermal, microwave (MW) and THz biasing have been studied at 0.65 THz and 4.2 K in detail. The current responsivity and noise equivalent power (NEP) have been measured and compared respectively. The detectors with the MW and THz biasing have about one order higher current responsivity than that of the thermal one. With the MW biasing, an NEP at the order of $\mathrm{pW}/\surd\mathrm{Hz}$ is obtained by choosing the MW frequency and power appropriately.