SiO_2薄膜折射率的准确拟合分析

精确的光学常数对于设计和制备高品质的光学薄膜非常重要,尤其是那些光学性能对折射率变化敏感的薄膜。SiO_2是一种常用的低折射率材料,因与常用基底折射率相近使其准确拟合有一定难度。实验通过离子束溅射制备了SiO_2单层膜。考虑测量时的误差和基底折射率的影响,采用透射率包络和反射率包络得到了SiO_2的折射率,并用所得折射率进行反演来对这两种途径在实际测量拟合过程中的准确性进行比对。分析表明,剩余反射率在实际的测量过程中误差更小,直接用测量镀膜前后基片的剩余反射率值可以更简便更准确地得到SiO_2的折射率,能达到10~(-2)的精度。

It is very important to obtain the accurate optical constants of thin films for the design and the manufacture of high-quality optical coatings, especially for those optical characteristics very sensitive to the variation of refractive index. SiO<inf>2</inf> as a common low refractive index material is difficult in accurately fitting the optical constants which are close to those of the substrates. In this paper, single layer SiO<inf>2</inf> film is prepared by ion beam sputtering. Considering the error in measurement and the influence of the substrate refractive index, the refractive index of SiO<inf>2</inf> is obtained by the transmission envelop and the reflection envelop methods. The accuracies of these two methods are compared by inverting the obtained refractive index. The analysis shows that the refractive index of SiO<inf>2</inf> with 10^-2 precision can be well obtained by directly using the residual reflection of substrate and films because of the few errors in actual measurement of residual reflection.