Accurate method for determining the refractive-index profiles of planar waveguides in uniaxial media with the optical axis normal to the surface

Abstract

A new method for characterization of uniaxial planar waveguides from their measured effective mode indices is presented. The theory is outlined and expressions for efficient computer analysis are given. Uniaxial waveguide samples have been made in c-cut LiNbO(3) by proton exchange with and without post annealing in order to test the method on both steplike and graded-index profiles. The resulting characterization of the samples is discussed in relation to the inverse WKB method. Finally, the importance of incorporating the effects of material birefringence in the characterization of these kinds of waveguides is investigated.