NOISE BANDWIDTH OF DIFFUSION-COOLED HOT-ELECTRON BOLOMETERS

We present studies of the input and output noise of diffusion cooled h ot-electron bolometer mixers. By simultaneously measuring the gain and noise (with a 14 GHz LO) as a function of intermediate frequency for a 0.16 mu m diffusion cooled Nb device, we shaw that the noise bandwid th (4 GHz) is larger than the gain bandwidth (2.4 GHz). The output noi se is 55 K, and the mixer noise is very low, 340 It DSB. This shows th at diffusion cooled devices have low noise over a broad enough interme diate frequency band for practical applications in THz receivers.