Capote Elenna M, Gleckl Amy, Guerrero Jazlyn, Rezac Michael, Wright Robert, Smith Joshua R
J Opt Soc Am A Opt Image Sci Vis. 2021 Apr 1;38(4):534-541. doi: 10.1364/JOSAA.415665.
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 (silica) and : (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 and two of :. 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.
由非晶氧化物薄膜形成的光学涂层在精密测量中有许多应用。先进激光干涉引力波天文台（LIGO）和先进处女座探测器（Advanced Virgo）使用二氧化硅（SiO₂）涂层和二氧化钛掺杂钽酸锂（LiTaO₃:TiO₂）涂层，并在沉积后在500°C下退火，以实现低热噪声和低光吸收。这些涂层引起的光散射是探测器灵敏度的关键限制因素。本文描述了在熔融石英衬底上对单层离子束溅射薄膜进行的光散射测量：两个SiO₂样品和两个LiTaO₃:TiO₂样品。使用成像散射仪在12.8°的固定散射角下，在真空中将每个样品沉积后退火至500°C的过程中评估其光散射的原位变化。观察到四个镀膜光学元件中的三个在退火过程中散射减小，钽酸锂散射减小25%-30%，二氧化钛掺杂钽酸锂散射减小高达74%，而第四个样品的散射保持不变。在真空退火前后进行的角度分辨散射测量表明，四个样品中的三个有一定改善。这些结果表明，单层钽酸锂和二氧化钛掺杂钽酸锂薄膜在真空中进行沉积后退火不会导致散射增加，实际上可能会改善其散射。
