Performance of cryogenic microbolometers and calorimeters with on-chip coolers

摘要

Astronomical observations of cosmic sources in the far-infrared and X-raybands require extreme sensitivity. The most sensitive detectors are cryogenicbolometers and calorimeters operating typically at about 100 mK. The last stageof cooling (from 300 mK to 100 mK) often poses significant difficulties inspace-borne experiments, both in system complexity and reliability. We addressthe possibility of using refrigeration based on normalmetal/insulator/superconductor (NIS) tunnel junctions as the last stage coolerfor cryogenic thermal detectors. We compare two possible schemes: the directcooling of the electron gas of the detector with the aid of NIS tunneljunctions and the indirect cooling method, when the detector lattice is cooledby the refrigerating system, while the electron gas temperature is decreased byelectron-phonon interaction. The latter method is found to allow at least anorder of magnitude improvement in detector noise equivalent power, whencompared to the direct electron cooling.