Polarimetry at millimeter wavelengths with the NIKA and NIKA2 instruments

Magnetic fields play a crucial role in a large number of astrophysical processes from Galactic to Cosmological scales. They can be traced via observations of dust polarisation as demonstrated by several experiments like Archeops, SCUBA, ALMA and the Planck satellite. In particular, low resolution observations of dust polarisation have demonstrated that Galactic filamentary structures, where star formation takes place, are associated to well organised magnetic fields. High angular resolution polarisation observations could probe the physics at small angular scales and complete the current understanding of the star formation process: this is one of the main objectives of the NIKA2 camera. In NIKA2 as well as in its prototype, NIKA, the polarisation reconstruction consists in a quasi-simultaneous detection of the Stokes parameters Q and U, describing the linear polarisation of the light. This is achieved thanks to the continuous rotation of a modulator, a Half Wave Plate (HWP) and a polarizer coupled to the fast response of the Lumped Element Kinetic Inductance Detectors (LEKIDs). This PhD thesis focuses on the development of the NIKA polarimeter and consequently that of NIKA2, which observes the sky in intensity and polarisation from the IRAM 30 m telescope located in the Sierra Nevada (Spain). It presents the instrumental characterisation of the instrumental setup, the dedicated data analysis pipeline to reconstruct the polarisation properties of the observed source at the telescope and the science verification using known compact and extended sources observations. (author)