In-vacuum measurements of optical scatter versus annealing temperature for amorphous Ta₂O₅ and TiO₂:Ta₂O₅ thin films

Optical coatings formed from amorphous oxide thin films have many applications in precision measurements. The Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo use of S mathvariant="normal">i mathvariant="normal">O 2 (silica) mathvariant="normal">T : mathvariant="normal">a 5 (titania-doped tantala) post-deposition annealing to 500°C achieve low thermal noise optical absorption. scattering by these is a key limit the sensitivity detectors. This paper describes measurements for single-layer, ion-beam-sputtered on fused silica substrates: two samples . Using an imaging scatterometer at fixed angle 12.8°, in-situ changes scatter each sample were assessed during vacuum. three four coated optics was observed decrease process, 25–30% tantala up 74% titania-doped tantala, while fourth held constant. Angle-resolved performed before after vacuum suggest some improvement samples. These results demonstrate that post-deposition, high-temperature single-layer does not lead increase scatter, may actually improve their scatter.