Optical beam propagation in anisotropic media

Abstract

Optical diffraction in media with arbitrary inhomogeneous anisotropies (including linear birefringence and/or optical activity) is characterized by pronounced polarization effects. These effects have typically been analyzed by the coupled wave formalism. An alternative analytical technique is the anisotropic optical beam propagation method (BPM) first proposed by Thylen and Yevick.1 The BPM is a highly intuitive approach to solving the light propagation equation in an optically inhomogeneous medium. The coupled wave approach is preferred for spectrally pure inhomogeneities (simple gratings), whereas the BPM is the preferred algorithm for spectrally rich inhomogeneities (image modulated gratings). The BPM replaces the distributed diffraction problem with an equivalent lumped element approximation consisting of infinitesimally thin phase and polarization modulation planes separated by optically homogeneous layers. The evolution of the light profile both in the near field and in the plane wave spectrum can be monitored as the light beam propagates through the anisotropic medium. In this paper we extend the analysis to include optical activity for modeling volume grating in materials such as bismuth silicon oxide. We also perform detailed numerical experiments to assess which classes of problem are better suited for the coupled wave formalism and which for the BPM formalism.