Theoretical analysis has been conducted to investigate the contribution of free charge carriers to the optical properties in the infrared region of micrometer-thick porous silicon layers composed of anisotropic silicon nanocrystals. Calculations based on a generalized effective medium model, which accounts for the anisotropic shape of silicon nanocrystals and the interaction between the electric field of a light wave and mobile charge carriers in the nanocrystals, indicate a strong dependence of the polarization anisotropy of the reflection, absorption, and transmission coefficients of silicon films on the concentration of free charge carriers. For charge carrier concentrations ranging from 10^16 to 10^20 cm^(-3), significant birefringence and linear dichroism (absorption anisotropy) are observed, along with a non-monotonic dependence of the refractive index, reflection, and transmission coefficients on the concentration of charge carriers. These findings can be applied to develop optical switches and modulators for processing optical signals in silicon photonic elements.
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.05.Xj Metamaterials for chiral, bianisotropic and other complex media
$^1$Department of Low Temperature Physics and Superconductivity., Faculty of Physics, M.V.Lomonosov Moscow State University
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