Superconducting noise bolometer for terahertz radiation

Abstract

We present a superconducting noise bolometer that is a bolometric detector sensing radiation via radiation-induced changes of its own microwave noise. The detector represents a nano-strip made from a thin NbN superconducting film. It operates in the superconducting state and carries a supercurrent slightly less than the critical current. Radiation couples with the detector via an immersion lens and a planar antenna, which jointly define the useful spectral range from 1 to 5 THz. At an ambient temperature of 4.2 K the optically measured noise-equivalent power amounts at ≈ 10^-13 W Hz^-1/2 along with a time-constant of approximately 150 ps.