High Sensitivity W-Band LEKID-Based on-Chip Polarimeter

We have developed and characterized an on-chip polarimeter based on Lumped Element Kinetic Inductance Detectors (LEKIDs) optimized for the whole W -band frequency range ($\mathbf{7 5 - 1 1 0} \mathbf{G H z}$). The chip consists of two $\mathbf{3} \times \mathbf{3}$ LEKID arrays fabricated on opposing faces of a silicon substrate. Both arrays have been fabricated from a titanium/aluminum superconducting bilayer and they present orthogonal inductor orientations to resolve horizontal and vertical polarization modes. A second silicon substrate is coated at its rear part with an aluminum thin film and works as a back-reflector to enhance the forward absorption efficiency via constructive interference. In this work, we report the absorption response and performances in the $W$ band of this on-chip polarimeter configuration in both polarizations at cryogenic temperatures. The noise spectrum and the noise equivalent power (NEP) is also characterized using a blackbody source at two different temperatures to demonstrate its functionality.