EQUIVALENCE OF EXTRAORDINARY WAVES IN A UNIAXIAL MEDIUM AND SCALAR WAVES IN VACUUM

Abstract

We use the of the wave-vector surface in uniaxially anisotropic media to con- struct an equation for the amplitude or extraordinary waves. This equation is identical to the one derived directly from MaxwelPs equations for the component of the electric field vector parallel to the optic axis. In principal axis coordinates, the extraordinary wave equation is a scaled version of the scalar He!mholtz equation. Consequently, there is a one-to-one correspondence between extraordinary waves and scalar waves in vacuum. This equivalence can be used to find the solution of problems on diffraction and beam propagation in uniaxial media from known solutions of the corresponding isotropic 'prob- lems. As a simple example we determine the size of the focal region of converging beams in uniaxial crystals.