Speaker
Description
The University of Sannio and the University of Salerno joined forces to develop advanced optical coatings for 3G gravitational wave detectors.
We own a fully programmable plasma-assisted e-beam optical-coating deposition system with sub-nm accuracy/repeatability, using up to 6 different materials in a single batch, and state-of-the-art thin-film characterization facilities including AFM, STM, XRD, SEM and TEM.
Identifying cryo-compatible high and low index optical materials (free from the well known blow-up of mechanical losses at cryo-temperatures observed in the materials used in 2G detectors) is a key problem for ET.
Recent results, obtained in collaboration with NTHU, demonstrated that nanolayered composites made by a glassy but not cryo-friendly material like Silica, and a cryo-friendly material but prone to crystallization upon annealing like Titania tolerate very high post-deposition annealing temperatures without crystallizing, and do not exhibit a cryogenic mechanical-loss peak.
In the light of these results, nanolayered Silica/Alumina composites are suggested as an excellent candidate low-index (n~1.6) cryo-friendly coating material for ET, possibly better than currently candidate Silica-doped Hafnia (n~1.8) .
The expected performance of a whole 5ppm transmittance coating based on a-Si and nanolayered SiO2::Al2O3 will be illustrated together with our deposition and testing plans for the next months.
