High-Reflection Coatings for Gravitational-Wave Detectors:<i>State of The Art and Future Developments</i>

We report on the optical, mechanical and structural characterization of the sputtered coating materials of Advanced LIGO, Advanced Virgo and KAGRA gravitational-waves detectors. We present the latest results of our research program aiming at decreasing coating thermal noise through doping, optimization of deposition parameters and post-deposition annealing. Finally, we propose sputtered Si3N4as a candidate material for the mirrors of future detectors.