Power load dependencies of cold electron bolometer optical response at 350 ghz
Michael A. Tarasov, Valeryan S. Edel'man, Andrey B. Ermakov, Sumedh Mahashabde, L. S. Kuzmin
Abstract
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.