To optimise the optical performances of a future space instrument dedicated to CMB polarisation observations, it will be very interesting to reduce the physical size of the focal plane without decreasing the number of detectors. An elegant way to reach such architecture would be to use multichroic detectors that are sensitive to multiple frequency bands. A large bandwidth antenna could be used to feed multiple detectors (TESs or KIDs) through different bandpass filters. A first architecture has been defined within an ESA contract between some European partners (universities of Manchester, Maynooth, Chalmers, Roma la Sapienza and APC).

The goal will be to optimise and realize a first prototype working at 150GHz with few bands and relatively low spectral resolution (R~10). The antenna, the filter bank and the KIDs detectors will be integrated on a planar structure. The study will concentrate on the optimisation of large bandwidth antenna together with the filter bank and the coupling with the detector. The optimisation will be done using the modeling softwares and facilities available at APC (CST-MWS, Sonnet, dilution fridge, adiabatic demagnetization fridge, 70GHz-250GHz vector network analyser). Samples will be realized in the clean room facility of Observatoire de Paris as well as in C2N-MINERVE (Orsay).

According to the exact competences and preferences of the student, we could focus her/his activity on one or two of the key aspects: a) modeling and design; b) characterizations at cryogenic temperatures; c) micro-fabrication. The candidate should have competences in at least one of the following domains: RF (radio-frequency) design, instrumentation for astronomy, microfab technologies.