Dual-Polarization-Sensitive Kinetic Inductance Detectors for Balloon-borne Sub-millimeter Polarimetry.

We are developing arrays of kinetic inductance detectors for sub-millimeter polarimetry that will be deployed on the BLAST balloon-borne instrument. The array is feedhorn-coupled, and each pixel contains two lumped-element kinetic inductance detectors (LEKIDs) made of TiN. The absorbing, inductive sections of the LEKID-pair are orthogonal, which allows simultaneous measurement of both horizontal and vertical polarizations within one spatial pixel. In this paper, we show efficient absorption in TiN films when coupled to waveguide at room temperature and present dark measurements of single polarization devices with varying capacitor geometries. We show that it will be difficult to achieve background-limited performance in BLAST with stoichiometric TiN films with T $$_{c}=4.5$$ K, and that non-stoichiometric films with lower T $$_{c}$$ will be required. [ABSTRACT FROM AUTHOR]