Far-infrared/submillimeter imager-polarimeter using distributed antenna-coupled transition edge sensors

Abstract

We describe a new concept for a detector for the submillimeter and far infrared that uses a distributed hot-electron transition edge sensor (TES) to collect the power from a focal-plane-filling slot antenna array. Because superconducting transmission lines are lossy at frequencies greater than about 1 Thz, the sensors must directly tap the antenna, and therefore must match the antenna impedance (~ 30 ohms). Each pixel contains many TESs that are all wired in parallel as a single distributed TES, which results in a low impedance that can match to a multiplexed SQUID readout. These detectors are inherently polarization sensitive, with very low cross-polarization, but can also be easily configured to sum both polarizations for imaging applications. The single polarization version can have a very wide bandwidth of greater than 10:1 with a quantum efficiency greater than 50%. The dual polarization version is narrow band, but can have a higher quantum efficiency. The use of electron-phonon decoupling obviates the need for micro-machining, making the focal plane much easier to fabricate than with absorber-coupled, geometrically isolated pixels. An array of these detectors would be suitable for an imager for the Single Aperture Far Infrared (SAFIR) observatory. We consider two near-term applications of this technology, a 32 x 32 element imaging polarimeter for SOFIA and a 350 µm camera for the CSO.