Propagation of light pulses in nonisotropic media

We derive the propagation equation for the slowly varying envelope (SVE) of the electric field in a homogeneous dispersive nonisotropic medium. Terms in the propagation equation of the field envelope that originate because of finite beam size are obtained and explained, including generalized Fresnel diffraction terms and a term that rotates the SVE wave packet in a uniaxial crystal about an axis perpendicular to the optical plane. Numerical estimates of these terms in the propagation of short pulses in the uniaxial crystal β-barium borate are presented. We obtain an analytic expression for the SVE for an initial Gaussian wave packet by keeping terms up to second order in the wave equation for the SVE.