Fast and interference fringe independent optical characterization of zinc oxide nano thin films using model-based genetic algorithm for optoelectronic applications

Abstract

In this article, a model-based genetic algorithm is used to determine the optical properties of nanostructured zinc oxide single-sided nano thin films that does not depend on the interference fringes of optical transmission spectrum. The functional form for refractive index n(λ) and absorption coefficient α(λ) as functions of wavelength instead of randomly organized genes corresponding to the optical parameters are used in the implementation of GA. Using the proposed model for the refractive index dispersion and absorption, the transmittance curves of zinc oxide thin films obtained from optimized parameters are fitted with the original spectrum. The calculated results give us R2 values higher than 0.950. Compared to traditional optimization methods, the fitting error of genetic algorithm is typically smaller. The interference fringes are not critical to perform the genetic algorithm in comparison to the classical methods such as the envelope method. One of the advantages for this technique is its considerable speed and there is no need for successive parabolic interpolation and extra calculations. This technique allows the use of available data corresponding to the optical responses such as transmission or reflection of single layered or multilayered structures simply by changing the cost function.