Cold-electron bolometer array integrated with a 350 GHz cross-slot antenna

Paper in proceeding, 2010

Two series/parallel arrays of Cold-Electron Bolometers (CEB) with Superconductor-Insulator-Normal (SIN) tunnel junctions were integrated in orthogonal ports of a cross-slot antenna. The receiving system was designed for polarisation measurements in a 350 GHz frequency band with JFET readout at the BOOMERanG-FG balloon telescope. Each orthogonal array consists of 10 cold-electron bolometers connected in parallel for RF signal and in series for DC signal. The array was designed to increase the output resistance by a factor of 102 in comparison to a single CEB, for matching with JFET readout while maintaining the same conditions for RF coupling. The dynamic resistance of such array is 1 M5 at the bias point of maximal response. For the input microwave signal bolometers are connected in parallel. This provides matching to the 30 input impedance of a cross-slot antenna on Si substrate. The array of bolometers has a saturation power 10 times higher than a single bolometer. This significantly increases the dynamic range. With a measured temperature response of 8.8 μV/mK, a total absorber volume of 0.08 μm3, and an output noise of about 11 nV/Hz1/2, we estimated the dark electrical noise equivalent power as NEP=6*10-18 W/Hz1/2 at 280 mK. The optical response was measured using both hot/cold loads and a backward wave oscillator as sources of radiation.