Adamson Peep
Institute of Physics, University of Tartu, Riia 142, Tartu 51014, Estonia.
Appl Opt. 2011 Jun 10;50(17):2773-83. doi: 10.1364/AO.50.002773.
The possibilities of determining the parameters of uniaxially anisotropic ultrathin nonabsorbing dielectric films on absorbing or transparent isotropic substrates by surface differential reflectance measurements are analyzed. The analysis is based on analytical reflection formulas obtained in the framework of a long-wavelength approximation. It is shown that, in the case of transparent substrates, it is always possible to determine the thickness of a uniaxially ultrathin film and its four parameters of anisotropy (optical constants n(o) and n(e) and angles θ and φ) simultaneously. However, for such films on absorbing substrates, it is possible to decouple the thickness and optical constants by differential reflectance measurements only if θ≠0. The accuracy of the obtained analytic formulas for determining the parameters of ultrathin films is estimated by computer simulations where the reflection problem was solved numerically on the basis of the rigorous electromagnetic theory for anisotropic layered systems.
分析了通过表面微分反射率测量来确定吸收性或透明各向同性衬底上的单轴各向异性超薄非吸收性介电薄膜参数的可能性。该分析基于在长波长近似框架下获得的解析反射公式。结果表明，在透明衬底的情况下，总是可以同时确定单轴超薄膜的厚度及其四个各向异性参数（光学常数n(o)和n(e)以及角度θ和φ）。然而，对于吸收性衬底上的此类薄膜，仅当θ≠0时，才有可能通过微分反射率测量来解耦厚度和光学常数。通过计算机模拟估计了用于确定超薄膜参数的所得解析公式的精度，其中基于各向异性分层系统的严格电磁理论对反射问题进行了数值求解。
