Work Package 4: Development of low loss dielectric coatings for advanced detectors Scientific motivation: Mechanical dissipation from dielectric mirror coatings is predicted to be a significant source of thermal noise for advanced detectors. Coatings must also be of low optical loss. - Main workpackage outcomes/long term aim: Definition of a low-mechanical-loss optical coating design/production process suitable for advanced detectors operating at either room or cryogenic temperatures - Groups involved: Institute for Gravitational Research, University of Glasgow Laboratoire des Matériaux Avancés, (LMA) Lyons AURIGA group, Laboratori Natzionali di Legnaro (+Leiden/Rome) Materials group, VIRGO, Perugia ESPCI, Laboratoire d'Optique, Paris

Work Package 4: Development of low loss dielectric coatings for advanced detectors Milestones Year 1Report from Glasgow Group (IGR) Production of the first SiO 2 /Ta 2 O 5 and SiO 2 /Al 2 O 3 coatings Status: Coatings procured from REO and Waveprecision. Deliverables Year Loss measurements on SiO 2 /Ta 2 O 5 at room T Status: Given the availability of results from work by the LIGO project on SiO 2 /Ta 2 O 5 we chose to pursue studies of Al 2 O 3 /Ta 2 O 5 coatings (relevant for use with sapphire mirror substrates) We have previous experimental measurements which we are re- analysing in greater depth for this project given our new work on FEA and improved interpretation of sources of coating dissipation. This work is continuing as planned Loss measurements on SiO 2 /Al 2 O 3 at room T Status: A SiO 2 /Al 2 O 3 coating on sapphire has been procured – we plan to carry out measurements of the coating mechanical loss. This work is continuing as planned.

Facility to measure the Q of coated membranes realized under the EGO R&D program and delivered to Lyon Report from INFN Perugia

The Michelson Morley InterferometerData analysis program Preliminary measurements in Perugia for clamping design

Work Package 4: Development of low loss dielectric coatings for advanced detectors Milestones of STREGA proposal for next year: Milestone Year 2production of first SiO 2 /high index material Deliverables Year 2measurements on silica substrate identification of diffraction coating production process Scientific plan for next year: Some EGO funding is approved for coating research - LMA Lyons We propose –Substrates to be provided by collaborating STREGA institutions –Thin ‘membranes’ to be used initially for fast test measurements (INFN Perugia)

Work Package 4: Development of low loss dielectric coatings for advanced detectors Scientific plan for next year, cont. - Smaller number of larger ‘mirror-like’ samples for further study in more realistic configurations INFN Perugia, Glasgow (participation by Legnaro/Leiden/Rome) - Move over coming year to study coatings on some silicon substrates (for use at 1064nm initially) - Choice of specific coatings – doping etc – subject of near future discussion – propose WP4 meeting in Lyons Costs an issue..