Arrays of Annular Antennas With SINIS Bolometers

For improving the dynamic range and sensitivity at high power load, we have integrated superconductor-insulator-normal metal-insulator-superconductor (SINIS) bolometers with a frequency selective surface (FSS)-based distributed absorber formed by a series and parallel array consisting of 25 annular antenna elements, each containing two SINIS bolometers. By using a design with 50 bolometers, we reduce incident power load on each bolometer, increase sensitivity and saturation power which is important for ground-based and balloon-borne telescopes with high background power loads. Our main detector pixel is optimized for a frequency band centered at 345 GHz. The detectors are matched to incoming telescope beam by a back-to-back horn with a back reflector. Such a configuration improves both the efficiency and the bandwidth of the receiver. Measured voltage responsivity approaches 2*10
⁹
V/W with an amplifier-limited voltage noise of 20 nV/Hz
^1/2
, which corresponds to a NEP = 10
^-17
W/Hz
^1/2
. The linear voltage response for incoming power is observed for absorbed power of about 5 pW. The current responsivity for parallel array is 2*10
⁴
A/W and the shot noise limited intrinsic noise equivalent power is NEP = 5*10
^-18
W/Hz
^1/2
. The noise equivalent temperature difference is NETD = 100 μK/Hz
^1/2
at 2.7-K background radiation temperature.