Propagation of polarized light through two- and three-layer anisotropic stacks

The extended Jones formulation is used to investigate propagation at nonnormal incidence through two- and three-layer systems of birefringent material in which the optic axes of the individual layers are in the plane of the layers. Such systems are equivalent to two optical elements in series-an equivalent retardation plate and a polarization rotator. Analytical solutions are obtained for the equivalent retardation and rotation. The major finding is that, in general, there are two nonnormal incidence directions for which the retardation vanishes; therefore these two directions are optic axes of the composite system. These simple layered systems therefore behave in a manner similar to biaxial crystals. Moreover, the results illustrate the fact that even if the optic axes of individual layers in composite systems are in the plane of the layers, the optic axes of the system are, in general, out of this plane.