Ultrasensitive hot-electron microbolometers with Andreev reflection for submillimeter-wave radio astronomy: A review

A review is given of the theoretical and experimental research into the per formance of ultrasensitive hot-electron microbolometers implementing Andree v reflection in the context of submillimeter-wave radio astronomy. To measu re the irradiation-induced increment in the electron temperature of the abs orber, two types of sensor may be employed: superconductor/insulator/normal -metal sensors and electrothermal-feedback transition-edge sensors. A compa rative study of microbolometers with these sensors is carried out. It is sh own that the latter design has certain advantages if the sensor is integrat ed with the absorber. For such designs, possible ways to minimize the noise equivalent power are discussed. Techniques of matching the transition-edge microbolometer in hand to the incident radiation and the output-signal pro cessor are covered as well. They use a planar antenna and a superconducting picoammeter, respectively.