Andryieuski Andrei, Lavrinenko Andrei V, Zhukovsky Sergei V
DTU Fotonik, Technical University of Denmark, Ørsteds pl. 343, Kongens Lyngby, 2800 Denmark.
Nanotechnology. 2015 May 8;26(18):184001. doi: 10.1088/0957-4484/26/18/184001. Epub 2015 Apr 16.
We present a comprehensive analysis of the applicability of the effective medium approximation to deeply subwavelength (period ≤λ/50 all-dielectric multilayer structures. We demonstrate that even though the dispersion relations for such multilayers differ from the effective medium prediction only slightly, there can be regimes when an actual multilayer stack exhibits significantly different properties compared to its homogenized model. In particular, reflection near the critical angle is shown to strongly depend on even very small period variations, as well as on the choice of the multilayer termination. We identify the geometries for which the influence of the subwavelength features is maximized and demonstrate that the difference between the reflectance from the actual multilayer and the effective medium prediction can be as great as 0.98. The results of this analysis can be useful for high-precision multilayer ellipsometry and in sensing applications.
我们对有效介质近似在深亚波长（周期≤λ/50）全介质多层结构中的适用性进行了全面分析。我们证明，尽管此类多层结构的色散关系与有效介质预测仅略有不同，但在某些情况下，实际的多层堆叠与其均匀化模型相比可能表现出显著不同的特性。特别是，临界角附近的反射被证明强烈依赖于非常小的周期变化以及多层终端的选择。我们确定了亚波长特征影响最大化的几何结构，并证明实际多层结构的反射率与有效介质预测之间的差异可能高达0.98。该分析结果可用于高精度多层椭偏测量和传感应用。
