激光量热法测量光学薄膜微弱吸收

Measuring Weak Absorptance of Optical Thin Films with Laser Calorimetric Technique

按照国际标准ISO 11551研制了用于测量光学薄膜微弱吸收的激光量热装置。典型情况下吸收测量灵敏度优于10-6,测量误差估计为10%左右。在1064 nm波长测量1 mm厚石英玻璃基板的绝对吸收为3.4×10-6,测量灵敏度达到1.5×10-7。测量了不同膜层设计、不同使用角度、不同镀膜技术镀制的全介质高反膜样品;使用离子束溅射(IBS)技术镀制的Ta2O5/SiO2多层0°反射镜的吸收仅为1.08×10-5,而使用离子束辅助沉积(IAD)技术镀制的HfO2/SiO2多层45°反射镜的吸收测量值为6.83×10-5。

A laser calorimeter in compliance with ISO 11551 was developed to measure the absolute absorptance of optical thin films. Under a typical condition the absorptance sensitivity of the calorimeter was better than 10^-6 and the measurement error was estimated to be -10%. For an uncoated fused silica substrate with 1-mm thickness, the measured absorptance was 3.4×10^-6 and the sensitivity was -1.5× 10^-7. The laser calorimeter was employed to measure the absorptance of highly reflective dielectric coatings prepared by two different coating techniques. The absolute absorptance of a 0° Ta2O5/SiO2 multilayer mirror prepared by the ion beam sputtering （IBS） technique was as low as 1.08×10^-5 , and the absorptance of a 45°HfO2/SiO2 multilayer mirror prepared by the ion-assisted deposition （lAD） technique was 6.83×10^-5, respectively.