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

We are developing a Transition-edge Hot-electron Microbolometer (THM) with the capacity to make sensitive and broadband astrophysical observations over frequencies ranging from 30-300 GHz (10-1 mm). This micron-sized bolometer consists of a superconducting bilayer Transition-Edge Sensor (TES) and a thin-film absorber. The THM employs the decoupling between electrons and phonons at low temperatures (below 300 mK) to provide thermal isolation. The devices are fabricated photolithographically and read out with Superconducting Quantum Interference Devices (SQUIDs). We present the details of a thermal model for a THM detector and the design for new thermally optimized antenna-coupled THMs for illumination by a RF source at 40 and 100 GHz.