Optical coatings formed from amorphous oxide thin films have many applications in precision measurements. The Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo use coatings of ${\rm{Si}}{{\rm{O}}_2}$ (silica) and ${\rm{Ti}}{{\rm{O}}_2}:{\rm{T}}{{\rm{a}}_2}{{\rm{O}}_5}$ (titania-doped tantala) and post-deposition annealing to 500°C to achieve low thermal noise and low optical absorption. Optical scattering by these coatings is a key limit to the sensitivity of the detectors. This paper describes optical scattering measurements for single-layer, ion-beam-sputtered thin films on fused silica substrates: two samples of ${\rm{T}}{{\rm{a}}_2}{{\rm{O}}_5}$ and two of ${\rm{Ti}}{{\rm{O}}_2}:{\rm{T}}{{\rm{a}}_2}{{\rm{O}}_5}$. Using an imaging scatterometer at a fixed scattering angle of 12.8°, in-situ changes in the optical scatter of each sample were assessed during post-deposition annealing to 500°C in vacuum. The scatter of three of the four coated optics was observed to decrease during the annealing process, by 25–30% for tantala and up to 74% for titania-doped tantala, while the scatter from the fourth sample held constant. Angle-resolved scatter measurements performed before and after vacuum annealing suggest some improvement in three of the four samples. These results demonstrate that post-deposition, high-temperature annealing of single-layer tantala and titania-doped tantala thin films in vacuum does not lead to an increase in scatter, and may actually improve their scatter.

中文翻译：

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非晶态Ta ₂ O ₅和TiO ₂：Ta ₂ O ₅薄膜的光散射真空度与退火温度的关系

由非晶氧化物薄膜形成的光学涂层在精密测量中具有许多应用。先进的激光干涉仪重力波天文台（LIGO）和先进的处女座使用$ {\ rm {Si}} {{\ rm {O}} _ 2} $（二氧化硅）和$ {\ rm {Ti}} {{ \ rm {O}} _ 2}：{\ rm {T}} {{\ rm {a}} _ 2} {{\ rm {O}} _ 5} $（掺杂二氧化钛的塔塔拉）和沉积后退火至500 °C可实现低热噪声和低光吸收。这些涂层的光散射是探测器灵敏度的关键限制。本文介绍了在熔融石英衬底上单层离子束溅射薄膜的光散射测量：$ {\ rm {T}} {{\ rm {a}} _ 2} {{\ rm {O }} _ 5} $和其中两个$ {\ rm {Ti}} {{\ rm {O}} _ 2}：{\ rm {T}} {{\ rm {a}} _ 2} {{\ rm {O}} _ 5} $。使用成像散射仪以固定的12.8°散射角，在真空中进行沉积后退火至500°C的过程中，评估了每个样品的光学散射的原位变化。观察到，在退火过程中，四个镀膜光学器件中的三个的散射减小，坦塔拉减少了25％至30％，二氧化钛掺杂的坦塔拉高达74％，而第四个样品的散射保持恒定。真空退火前后进行的角度分辨散射测量表明，四个样品中的三个样品有所改善。这些结果表明，在真空中对单层塔塔拉和掺杂二氧化钛的塔塔拉薄膜进行沉积后的高温退火不会导致散射的增加，实际上可以改善其散射。