[en] Nuclear fusion represents one of the best chances humanity has to detach itself from fossil fuels for energy production, in an effort to tackle the issues related with global warming. The delicate plasma equilibrium necessary to reach stable operation requires a wide array of different diagnostics capable of continuously monitoring the various plasma parameters and to counteract the insurgence of instabilities that naturally arise inside a tokamak. Polarimetry is among these techniques, having being proven as a reliable instrument in decades of nuclear fusion research applications. By measuring the rotation induced into the polarization plane of an electromagnetic wave traveling through the plasma, important parameters like the current density and the poloidal magnetic field can be reconstructed. This thesis studies the application of Kinetic Inductance Detectors (KID) based on sapphire and diamond substrates as the sensitive component of an innovative polarimetric diagnostic system. These kind of devices are characterized by a very simple construction, consisting in a single superconducting thin layer patterned to form an LC resonating circuit. Incoming photons with sufficient energy break down Cooper pairs within the superconductor, changing its surface impedance. This leads to a change of the resonance frequency and phase of the resonators that can be detected with standard radio frequency techniques. The adopted design includes a multi-pixel configuration with polarization sensitiveness for single detector operation. The design and production phase of the prototypes was preceded by an extensive simulation and modelization study performed to evaluate the range of operating frequencies of the resonators, to investigate the occurrence of cross-talk between the pixels present on the detector and to assess the coupling strength between the resonators and the feedline, with the aim of optimizing the detectors for the application at hand. The produced prototypes where then characterized with measurements that include the critical temperature and current of the deposited films, the resonators response to an excitation tone and to incoming THz radiation. The usage of diamond as a substrate for these kind of devices is proposed here for the first time to the best of our knowledge. The results obtained show how this material, characterized by exceptional mechanical, thermal and radiation hardness properties, represent a promising candidate for a fully optimized detector to be employed in future nuclear fusion power plants.