Antenna-coupled transition-edge hot-electron microbolometer

We are developing a new type of antenna-coupled superconducting bolometric detector for millimeterwave and sub-millimeterwave astrophysics. In this design, a planar antenna couples radiation from free space to the electron system in a small absorber. The absorber is in thermal contact with a small Transition-Edge Sensor (TES), which serves as a thermistor. At sub-Kelvin temperatures the thermal isolation between the electrons and the lattice in metals causes the incoming radiation to heat the normal electrons in the absorber and the TES without the need for micromachined thermal isolation structures. We call these detectors Transition-edge Hot-electron Microbolometers and are optimizing them for observations of the cosmic microwave background. The small volume (∼5 μm3) of the absorber and TES produces a short thermal time constant that facilitates rapid scanning of the sky. These devices can be coupled to arrays of dual-polarization antennas in large format focal planes and other optical systems. We have constructed a scale model of a candidate planar antenna and tested a Mo/Cu proximity effect TES and Cu absorbers.