Basic elliptical Gaussian wave and beam in a uniaxial crystal.

Electromagnetic beams in a uniaxial crystal are treated with emphasis on the extraordinary mode. A virtual source that generates a basic elliptical Gaussian wave propagating obliquely to the optic axis is identified. An exact expression is obtained for this basic elliptical Gaussian wave that simplifies to the corresponding basic elliptical Gaussian beam in the appropriate limit. In the direction of amplitude propagation, the paraxial result becomes identical to the exact result and the sum of all the nonparaxial contributions vanish. The characteristics of the basic elliptical Gaussian beam are illustrated with a numerical example. From the spectral representation of the basic Gaussian wave, the first three orders of nonparaxial corrections for the basic elliptical Gaussian beam are determined. The nonparaxial results reduce correctly to those of the fundamental Gaussian beam in an isotropic medium.