We report on the measurement of a very low noise equivalent power of 3× 10− 19 W/Hz 1/2
at 620 GHz in a superconducting antenna-coupled hot-electron bolometer. The sensing
element is a micron-size titanium transition-edge sensor with NbTiN superconducting
contacts fabricated on a sapphire substrate. The high sensitivity is due to the small device
volume, low operating temperature, and weak electron-phonon coupling in titanium film.
Measurements were done using a cryogenic black body emitter producing well-controlled …