New results for NbN phonon-cooled hot electron bolometric mixers above 1 THz

NbN Hot Electron Bolometric (HEB) mixers have produced promising results in terms of DSB receiver noise temperature (2,800 Ii at 1.56 THz). The LO sou rce for these mixers is a gas laser pumped by a CO2 laser and the device is quasi-optically coupled through an extended hemispherical lens and a self- complementary log-periodic toothed antenna. NbN HEBs do not require submicr on dimensions, can be operated comfortably at 4.2 Ii or higher, and require LO power of about 100-500 nW. IF noise bandwidths of 5 GHz or greater have been demonstrated. The DC bias point is also not affected by thermal radia tion at 300 K. Receiver noise temperatures below 1 THz are typically 450-60 0 Ei and are expected to gradually approach these levels above 1 THz as wel l. NbN HEB mixers thus are rapidly approaching the type of performance requ ired of a rugged practical receiver for astronomy and remote sensing in the THz region.