A Low-Noise Superconductive Nb Hot-Electron Mixer at 2.5 THz

We report on the development of a quasioptical Nb hot-electron bolometer mixer for a2.5 THz heterodyne receiver. The devices are fabricated from a 12 nm thick Nb film, and have a0.30 gmx0.15 gm in-plane size, thus exploiting diffusion as the electron cooling mechanism. Therf coupling was provided by a tvvin-slot planar antenna on an elliptical Si lens. A speciallydesigned 2.5 THz system, using a CO