Sensitivity Measurements of a Transition-Edge Hot-Electron Microbolometer for Millimeter-Wave Astrophysical Observations

Abstract Future experiments to probe the Cosmic Microwave Background (CMB) polarization will need arrays of 1000s of sensitive bolometers. We are developing a Transition-edge Hot-electron Microbolometer (THM) to fill this need. This small-volume bolometer consists of a superconducting bilayer Transition-Edge Sensor (TES) with a thin-film absorber. Unlike traditional monolithic bolometers which make use of micromachined structures, the THM employs the decoupling between electrons and phonons at milliKelvin temperatures to provide thermal isolation. The devices are fabricated photolithographically and are easily integrated with antennas via microstrip transmission lines, and with SQUID readouts. We present the results of noise, responsivity, and thermal conductance measurements in which electrical power is dissipated in the absorber, and confirm a thermal model for a test THM with a Mo/Au TES and Bi/Au absorber.