Thickness uniformity measurements and damage threshold tests of large-area GaAs/AlGaAs crystalline coatings for precision interferometry.
Thickness uniformity measurements and damage threshold tests of large-area GaAs/AlGaAs crystalline coatings for precision interferometry.
复制标题
用于精密干涉测量的大面积 GaAs/AlGaAs 晶体涂层的厚度均匀性测量和损伤阈值测试。
作者：
P. Koch;G. Cole;C. Deutsch;D. Follman;P. Heu;M. Kinley;R. Kirchhoff;S. Leavey;J. Lehmann;P. Oppermann;A. Rai;Z. Tornasi;J. Wöhler;D. Wu;T. Zederbauer;H. Lück
精密干涉测量是引力波天文学中极其灵敏测量的主要方法。介电涂层的热噪声限制了这些干涉仪的灵敏度。为了降低涂层热噪声，新型晶体 GaAs/AlGaAs 多层反射镜已被开发出来。迄今为止，尚未对这些替代低损耗涂层的表面形状和厚度均匀性进行研究。例如，表面形状误差会导致小角度散射，从而限制干涉仪的灵敏度。在这里，我们使用定制的扫描反射系统测量高反射、基底转移、结晶 GaAs/AlGaAs 涂层的表面形状。我们利用反射率随涂层厚度变化的事实。为了增加对涂层的穿透力，我们在中心波长为 1064 nm 的高反射涂层上使用了 1550 nm 激光。经测量，两英寸光学器件的 RMS 厚度变化为 0.41 ± 0.05 nm。该结果与 aLIGO 探测器的离子束溅射涂层实现的厚度均匀性（0.37 nm RMS）相差在 10% 以内。我们还测量了 GaAs/AlGaAs 涂层在 1064 nm 波长下的激光诱导损伤阈值下限为 64 MW/cm 2 。
Precision interferometry is the leading method for extremely sensitive measurements in gravitational wave astronomy. Thermal noise of dielectric coatings poses a limitation to the sensitivity of these interferometers. To decrease coating thermal noise, new crystalline GaAs/AlGaAs multilayer mirrors have been developed. To date, the surface figure and thickness uniformity of these alternative low-loss coatings has not been investigated. Surface figure errors, for example, cause small angle scattering and thereby limit the sensitivity of an interferometer. Here we measure the surface figure of highly reflective, substrate-transferred, crystalline GaAs/AlGaAs coatings with a custom scanning reflectance system. We exploit the fact that the reflectivity varies with the thickness of the coating. To increase penetration into the coating, we used a 1550 nm laser on a highly reflective coating designed for a center wavelength of 1064 nm. The RMS thickness variation of a two inch optic was measured to be 0.41 ± 0.05 nm. This result is within 10% of the thickness uniformity, of 0.37 nm RMS, achieved with ion-beam sputtered coatings for the aLIGO detector. We additionally measured a lower limit of the laser induced damage threshold of 64 MW/cm 2 for GaAs/AlGaAs coatings at a wavelength of 1064 nm.
影响因子：
35
作者：
Cole, Garrett D.;Zhang, Wei;Aspelmeyer, Markus
通讯作者：
Aspelmeyer, Markus