High-precision polarization measurements with lumped element kinetic inductance detectors

Aims. Our aim with this work is to demonstrate that two arrays of lumped element kinetic inductance detectors, when employed in filled array configuration and separated by an external linear polarizer oriented at 45°, 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. Methods. To achieve this, we characterized the uncertainties in the reconstruction of the polarization angle in the laboratory, using a dedicated closed-circuit 100 mK dilution cryostat. This was optically coupled to a Martin-Puplett interferometer and a custom-designed sky simulator equipped with both photometric and polarized sources, which allowed us to reproduce realistic ground-based observation conditions. With this experimental setup, we could generate intensity and polarization maps with diffraction-limited resolution, enabling us to determine the polarization angles and their associated uncertainties. Results. The results presented show that the polarization angle was reconstructed with an uncertainty of 6.5 arcmin. Conclusions. This work demonstrated the potential of lumped element kinetic inductance detectors used in a filled array configuration, achieving performance consistent with the requirements of next-generation Cosmic Microwave Background (CMB) experiments.