Normal-metal hot-electron microbolometer with on-chip protection by tunneljunctions

We describe recent developments in a fully on-chip integrated antenna-coupl ed bolometer for astrophysical applications at millimetre and submillimetre wavelengths. We have developed a normal-metal hot-electron microbolometer with Andreev mirrors for thermal protection of the absorber and the couplin g to the antenna. In previous experiments we could not operate the sensor a t temperatures below 300 mK presumably because of the high external noise l oad. Our latest results with the absorber protected by tunnel junctions sho w how this problem can be solved experimentally. We have achieved noise per formance mostly limited by the amplifier, which corresponds to expected det ector NEP on the order of 1.5 x 10(-17) W Hz(-1/2) at 100 mK.