Use of the optical admittance function and its WKB approximation to simulate and evaluate transmittance spectra of graded-index colloidal films

作者：Hild E^*; Deak A; Naszalyi L; Sepsi O; Abraham N; Horvoelgyi Z

来源：Journal of Optics A: Pure and Applied Optics , 2007, 9(10): 920-930.

DOI：10.1088/1464-4258/9/10/023

• graded-index film
• optical admittance function
• geometric optical (WKB) approximation
• antireflection
• colloidal films

A method is presented for the simulation of transmittance spectra of graded-index dielectric layers deposited on a transparent substrate of finite thickness, and the simulation process is applied to films of silica and zinc oxide nanoparticles. The method is based on the optical admittance by solving its differential equation for an appropriate refractive index profile. When the refractive index changes with depth Z according to the function N(Z) = N(0)/(1 + Z/zeta)(2), an exact solution exists which is equivalent to the WKB (geometric optical) approximate solution derived for the electromagnetic field in weakly inhomogeneous media. Using this solution allows us to characterize transparent graded-index films by two optical parameters - the mean refractive index and the grade of inhomogeneity, in addition to the film thickness through a fast curve fitting process.

• 出版日期2007-10