Characterization of TES bolometers used in 2-dimensional Backshort-Under-Grid (BUG) arrays for far-infrared astronomy

We have produced a laboratory demonstration of our new Backshort-Under-Grid (BUG) bolometer array architecture in a monolithic, 2-dimensional, 8 × 8 format. The detector array is designed as a square grid of suspended, 1 μ m thick silicon bolometers with superconducting molybdium/gold bilayer TESs. These detectors use an additional layer of gold bars deposited on top of the bilayer, oriented transverse to the direction of the current flow, for the suppression of excess noise. This detector design has earlier been shown to provide near fundamental noise limited device performance. We present results from performance measurements of witness devices. In particular we demonstrate that the inband excess noise level of the TES detectors is less than 20% above the thermodynamic phonon noise limit and not significantly higher out of band at frequencies that cannot be attenuated by the Nyquist filter. Our 8 × 8 BUG arrays will be used in the near future for astronomical observations in several (sub-)millimeter instruments.