NbN hot electron bolometric mixers at frequencies between 0.7 and 3.1 THz

The performance of NbN-based phonon-cooled hot electron bolometric (HEB) qu asioptical mixers is investigated in the 0.7-3.1 THz frequency range. The d evices are made from a 3.5-4 nm thick NbN film on high resistivity Si and i ntegrated with a planar spiral antenna on the same substrate. The length of the bolometer microbridge is 0.1-0.2 mu m; the width is 1-2 mu m. The best results of the DSB receiver noise temperature measured at 1.5 GHz intermed iate frequency are: 800 K at 0.7 THz, 1100 K at 1.6 THz, 2000 K at 2.5 THz and 4200 K at 3.1 THz. The measurements were performed with a far infrared laser as the local oscillator (LO) source. The estimated LO power requireme nt is less than 500 nW at the receiver input. First results on spiral anten na polarization measurements are reported.