Electromagnetic Gaussian beam beyond the paraxial regime

A modified electromagnetic beam technique is derived analytically from the asymptotic field expressions for the quasi-optical, millimeter-wave, plane polarized Laguerre-Gaussian modes of arbitrary order. The method makes use of the paraxial-wave formulas only, yet it accurately gives the full electric field vector at any point far beyond the conventional Gaussian beam regime. The technique is assessed numerically against the exact Green's function results.>