Quasi-optical description of wave beams in smoothly inhomogeneous anisotropic media

The quasi-optical description of wave beams is extended to smoothly inhomogeneous anisotropic and/or gyrotropic media. The method of consecutive expansion of Maxwellian equations is suggested for deriving scalar equations for the wave beam with narrow angular spectrum: first order equation is geometrooptical-like equation, second order is aberration-free one, third order equation includes cubic aberrations and so on. Equations are written along curved ray and describe focusing/defocusing of the beam due-to the ray curvature. The correct connection between the scalar beam amplitude and the vectorial electric field is conserved for every order.