Progress on background-limited membrane-isolated TES bolometers for far-IR/submillimeter spectroscopy

Abstract

To determine the lowest attainable phonon noise equivalent power (NEP) for membrane-isolation bolometers, we fabricated and measured the thermal conductance of suspended Si3N4 beams with different geometries via a noise thermometry technique. We measured beam cross-sectional areas ranging from 0.35 x 0.5 µm² to 135 x 1.0 µm² and beam lengths ranging from 700 µm to 8300 µm. The measurements directly imply that membrane-isolation bolometers are capable of reaching a phonon noise equivalent power (NEP) of 4 x 10ˉ²ºW/Hz¹/Ò . This NEP is adequate for the Background-Limited Infrarcd-Submillimctcr Spectrograph (BLISS) proposed for the Japanese SPICA observatory, and adequate for NASA's SAFIR observatory, a 10-meter, 4 K telescope to be deployed at L2. Further, we measured the heat capacity of a suspended Si<base>3N<base>4 membrane and show how this result implies that one can make membrane-isolation bolometers with a response time which is fast enough for BLISS.