supported partly by NSFC under Grants U1831202,U1731119,U1931123,11773083,and 11873099;the National Key R&D Program of China under Grants 2017YFA0304003 and 2018YFA0404701,CAS under Grants QYZDJ-SSW-SLH043 and GJJSTD20180003;Jiangsu Province under Grant BRA2020411.
Superconducting hot electron bolometer(HEB)mixers are the most sensitive heterodyne detectors at frequencies beyond 1 THz,and are used for many astronomical observations.HEB,consisting of a narrow and short supercondu...