Characterization of Picosecond-scale Response time of Superconducting NbN Hot Electron Bolometric mixers

Abstract A superconducting hot electron bolometer (HEB) mixer is an ultra-sensitive detector widely used for heterodyne detection of electromagnetic radiation, particularly at terahertz (THz) and submillimeter wavelengths. The response time of an HEB mixer is a critical parameter that defines its dynamic properties. In this work, we employ a pump-probe optical technique to investigate how the response time varies with temperature and bias voltage. Our measurements, conducted at 7 K under bias voltages of 1 mV and 2 mV, reveal a response time of approximately 40 ps. The pump-probe method was introduced to measure the HEB response time for the first time, overcoming conventional electronic bandwidth limitations and achieving picosecond-scale temporal resolution to characterize its ultrafast dynamics in the time domain. Additionally, the results not only reflect the intermediate frequency noise bandwidth performance of the device but also provide direct guidance for material and fabrication process verification.