Scalar field of nonparaxial Gaussian beams

A family of closed-form expressions for the scalar field of strongly focuse d Gaussian beams in oblate spheroidal coordinates is given. The solutions s atisfy the wave equation and are free from singularities. The lowest-order solution in the far field closely matches the energy density produced by a sine-condition, high-aperture lens illuminated by a paraxial Gaussian beam. At the large waist limit the solution reduces to the paraxial Gaussian bea m form. The solution is equivalent to the spherical wave of a combined comp lex point source and sink but has the advantage of being more directly inte rpretatable. (C) 2000 Optical Society of America.