Twin mirrors for laser interferometric gravitational-wave detectors.

Gravitational-wave detectors such as Virgo and the laser interferometric gravitational-wave observatory (LIGO) use a long-baseline Michelson interferometer with Fabry-Perot cavities in the arms to search for gravitational waves. The symmetry between the two Fabry-Perot cavities is crucial to reduce the interferometer's sensitivity to the laser amplitude and frequency noise. To this purpose, the transmittance of the mirrors in both cavities should be as close as possible. This paper describes the realization and the characterization of the first twin large low-loss mirrors with transmissions differing by less than 0.01%.

Ion beam sputtering coatings on large substrates: toward an improvement of the mechanical and optical performances.

Large mirrors (ø350 mm) having extremely low optical loss (absorption, scattering, wavefront) were coated for the VIRGO interferometer. The new generation of mirrors needs to have a better wavefront and lower mechanical loss. To improve the component wavefront, the corrective coating technique was used. By doping the tantalum pentoxide layers, we improved, for the first time to our knowledge, the multilayer mechanical loss. The first results are discussed.