High-precision polarization measurements with Lumped Element Kinetic Inductance Detectors

This work aims to demonstrate that two arrays of Lumped Element Kinetic Inductance Detectors (LEKIDs), when employed in filled array configuration and separated by an external linear polarizer oriented at 45 degrees, can achieve the precision required by next-generation cosmological experiments. The focus here is on validating their ability to meet stringent uncertainty requirements, in particular for polarization angle reconstruction. To achieve this, the uncertainties in the reconstruction of the polarization angle have been characterized in the laboratory using a dedicated closed-circuit 100 mK dilution cryostat. This is optically coupled to a Martin-Puplett interferometer and a custom-designed sky simulator equipped with both photometric and polarized sources, allowing one to reproduce realistic ground-based observation conditions. This experimental setup allows us to generate intensity and polarization maps with diffraction-limited resolution, allowing us to determine the polarization angles and their associated uncertainties. The results show performance in line with expectations for the next generation CMB experiments. The polarization angle was reconstructed with an uncertainty of 6.5 arcmin.