On the concept of a normal metal hot-electron microbolometer forspace applications

摘要

We present a theoretical analysis and experimental evaluation of a hot-electron microbolometer with normal metal absorber for ultrasensitive detecting infrared and submillimeter waves. The basic version of the antenna coupled microbolometer makes use of a hot-electron effect in the thin film resistive strip and Andreev reflection of hot electrons at SN interface between the strip and superconducting antenna. A value of NEP=5·10-18 W/Hz 1/2 for the thermal fluctuation noise and the thermal time constant t=0.2 μs at 300 mK have been estimated for one of the realized devices with thermal conductance G≈6·10-12 W/K. At 100 mK, the thermal conductance has been decreased to G≈7·10-14 W/K, that gives estimations for the thermal NEP=2·10-19 W/Hz1/2 and the time constant t=5 μs. An advanced version of the microbolometer includes also additional SIN junctions connected to the resistive strip for electronic cooling the absorber. Such microbolometer is intended as a detector of millimeter and submillimeter wave radiation for space applications