Nb superconducting hot electron bolometer mixers coupled with microstrip lines

The measured direct and heterodyne response of a quasi-optically coupled su perconducting Nh hot-electron bolometer mixer (HEBM) at 2.5 THz is reported . This mixer exploits a novel coupling circuit in which the microstrip line transformer is used to feed the If signal from the twin slot antenne to th e microbridge. The microstrip line is made of Au/SiO2/Al. Using a Fourier t ransform spectrometer, the frequency response of such a device is measured, we Rnd a peak response at a frequency of 1.9 THz, which is 20% lower than predicted, and a bandwidth of 1.6 THz: as we expect. By applying 2.5 THz ra diation from a far infrared Laser, we measure an uncorrected noise temperat ure T-N,T-rec of 4200 K.