A Superconducting Bolometer Antenna-Coupled to Terahertz Waves

The electrical performances and the optical response of a superconducting hotspot air-bridge bolometer (SHAB) coupled through a planar antenna to Terahertz waves and operating in vacuum at about 4.2 K, have been measured. The SHAB consists of a narrow Nb air bridge, voltage biased to form, in the middle of the suspended Nb stripe, a resistive hotspot, whose volume is modulated by the incoming radiation. The signal resulting from the coupled optical power and the device noise performance have been measured by using a home made transimpedance amplifier operating at room temperature, resulting in an electrical NEP of about 40 fW/Hz(1/2). Passive detection of the 300 K blackbody radiation at frequency lower than 1.6 THz, band limited by a low-pass optical filters, has been successfully carried out by using a SHAB.