Power load dependencies of cold electron bolometer optical response at 350 ghz

Paper in proceeding, 2014

Cold electron bolometers integrated with twin-slot antennas have been designed and fabricated. Optical response was measured in 0.06-0.6 K temperature range using black body radiation source at temperature 2-15 K. The responsivity of 0.3109 V/W was measured at 2.7 K radiation temperature. The estimated ultimate dark responsivity at 100 mK can approach Sv=1010 V/W and reduces down to 1.1108 V/W at 300 mK for the sample with absorber volume of 510-20 m3. At high power load levels and low temperatures the changes of tunneling current, dynamic resistance and voltage response have been explained by non-thermal energy distribution of excited electrons. Distribution of excited electrons in such system is of none-Fermi type, electrons with energies of the order of 1 K tunnel from normal metal absorber to superconductor instead of relaxing down to thermal energy kTe. This effect can reduce quantum efficiency of bolometer from hf/kTph in ideal case down to single electron per signal quantum in the high power case.