Applied Nanophotonics, Liquid Crystals and Biomedical Optics

A new method is proposed for simultaneous determination of thicknesses and refractive indices of multi-layers using double beam interference microscopes with centrally obscured or annulus aperture lens. The method is based on the fact that for centrally obscured apertures with high obstruction ratio (>0.9), the light angular spread is limited to a narrow interval, thus allowing for determination of the thicknesses and refractive indices using simple analytic expressions. It comprises of axial scanning for best interferogram contrast and subsequent path length scanning for best symmetry of the interferogram. With spectral scanning the absorption coefficients can also be determined using Kramers-Kroning relations.