Dielectrically embedded mesh half wave plate beam impact studies

An alternative solution to classic birefringent Half Wave Plates (HWP), based on the photolithographic techniques, has been recently developed. This new device can offer a very good alternative as a polarisation modulator for future CMB polarisation instruments. However, the systematic effects that this HWP will introduce in the overall instrument need to be investigated. We present a preliminary study of the impact of this dielectrically embedded HWP on the beam shape of a corrugated horn and its performance across the beam. Using a W-band Vector Network Analyser, we measured the co- and cross-polarisation beams of the HWP-horn system and the differential phase-shift introduced by the HWP across the beam. © 2012 SPIE.