New article in Optic Communications
The film optical parameters retrieval method based on Otto configuration is considered. The high sensitivity of the method in comparison to the ellipsometry is demonstrated. It is shown that the ellipsometric angles of reflection from the Otto configuration can be used for parameters retrieval. The method allows parameters retrieval without additional assumptions on the dielectric constant, being the reliable self consistent retrieval procedure.
The retrieval of thin film parameters from the reflection/transmission spectra is relevant procedure yet lacking the reliable tools. The existing wide spread methods rely on exploiting additional semiempirical assumptions in order to increase sensitivity.
The reasonable way to increase sensitivity is to increase the variations of the reflection/transmission coefficients: the retrieval procedure sensitivity to film parameters (dielectric permittivity ε and film thickness d) depends on the corresponding derivatives of reflection (transmission) coefficients ∂R∕∂ε (∂T∕∂ε) and ∂R∕∂d (∂T∕∂d). In this paper, we have considered ellipsometry in the Otto configuration for the problem. The configuration is used for the excitation of a surface plasmon polariton (SPP) on the metal surface. The resonant nature of the SPP excitation leads to a sharp change in the reflection coefficients in a small angular range, which means great values of ∂R∕∂ε and ∂R∕∂d. This can significantly improve the accuracy of the thin films parameters retrieval.
Contrary to widely used ellipsometry method, the usage of the Otto configuration makes possible to unambiguously determine the thickness and complex dielectric constant of the thin film. The ellipsometric angles Ψ and Δ as well as the reflection coefficient experience sharp variations with respect to film parameters changes. The high sensitivity of Ψ and Δ allows one to get rid of additional assumptions about the dielectric constant (using a specific dielectric dispersion model, Kramers–Kronig relation). Thus, the ellipsometry reliability can be significantly improved by utilizing the Otto configuration. The fact grants us with a promising technique of thin film parameters retrieval.
R.S. Puzko, A.I. Ivanov, E.S. Lotkov, I.A. Rodionov, I.A. Ryzhikov, A.V. Baryshev, A.M. Merzlikin
Optics Communications 456, 124636, 2020 (ImF 2.125)