Ellipsometry on very thick multilayer structures

We present a method that allows detailed analysis of complicated spectral e llipsometry spectra, such as those of thick (approximate to 10 mu m) multil ayer structures found in modern integrated optics devices. Ellipsometry sho uld be the natural choice for thorough nondestructive characterisation of t hose heterostructures, but extraction of the required parameters is often i mpracticable by common approaches. Our method is based on spline parametris ations of the unknown optical functions and is applicable to materials eith er with a smooth optical response or displaying sharp electronic transition s in the analysed energy range. We illustrate the method with results obtai ned on thick waveguide structures used for chemical sensors.