Submillimeter-Wave Hot-Electron Microbolometer with Andreev Reflection for Radioastronomy

Abstract

The main tasks of up-to-date submillimeter-wave radioastronomy requires application of superlow-temperature direct detectors (microbolometers) of micron and submicron dimensions built in special planar antennas matching them with input channels of receiving systems and injection of these systems by space vehicles out of the atmosphere to exclude the influence of atmospheric noise and absorption of radiation. Such measures are expected to allow us to obtain a noise equivalent power (NEP) of direct detectors up to 10-19–10-18 W/Hz1/2, which makes it possible to observe the majority of the weakest space radiation sources. The first studies and development of hot-electron microbolometers with Andreev reflection are performed. The NEP of such detectors estimated from dc measurements, corresponds to the above values. The first results of these studies also revealed difficulties of actual realization of the estimated NEP. The difficulties are related to radiation power losses due to imperfect matching in microwave channels and leakage of energy of electrons (acquiring an energy quantum from radiation and transferring it to phonons in the microbolometer absorber. Measures to reduce these losses are planned. A special two-stage cryostat for cooling both optical devices of the telescope built in the cryostat and the two-dimensional receiving array developed on the basis of the above-mentioned microbolometers and required for observing distributed radiation sources is designed within the framework of the Russian project for launching the submillimeter-wave space telescope. An efficient method for multiplexing signals in the receiving array is proposed.