Terahertz Power Detectors based on Superconducting HEBs with Microwave Readout

The properties of terahertz (THz) power detectors based on Superconducting NbN hot electron bolometer (HEB) with microwave (MW) readout are reported here. Features of relaxation oscillations probed with MW when the HEB is not pumped, pumped by THz source or heated by raising the bath temperature are studies. The periodic pulse in the reflected MW signals both in time and frequency domains show that the relaxation oscillation frequency increases with the bias voltage, incident THz power and/or bath temperature. The frequency count forms a quadratic polynomial fit to the bias voltage, a linear fit to the incident THz power and an exponential fit to the bath temperature. Based on the above results, incident THz power between 8-90 nW is measured using the HEB.