W-Band Superconducting Planar Orthogonal Mode Transducer Characterisation

The next generation of Cosmic Microwave Background (CMB) instruments is dedicated to the detection of CMB B-modes. Instruments like QUBIC (QU Bolometric Interferometer for Cosmology) need components with state of the art properties at high frequency (>90 GHz) to minimise instrumental systematic effects. The Orthogonal Mode Transducer (OMT) is a critical front end component as it allows the discrimination of the polarisation mode of light. Superconducting planar technology seems very promising to improve its properties and miniaturisation. We present a planar superconducting OMT operating in the W band (75–110 GHz). Design and simulations have been performed using CST Studio Suite. Laboratory characterisations were obtained with two different cryogenic setups. We will present these two cryogenic setups, the calibration procedure and preliminary results for two OMT samples.