A method to retrieve optical and geometrical characteristics of three layer waveguides from m-lines measurements

We consider three layer optical waveguides and present a method to measure simultaneously the refractive index and the thickness of each layer with m-lines spectroscopy. We establish the three layer waveguide modal dispersion equations and describe a numerical method to solve these equations. The accuracy of the method is evaluated by numerical simulations with noisy data and experimentally demonstrated using a PZT thin film placed between two ZnO layers.