Structure of the field of wave beams with circular polarization near a nonlinear focus in a cubic medium

An analysis is made of the structure of the field of wave beams focused in a nonlinear medium. Fields at the focal points can be determined from an equation which allows more accurately for diffraction. In the linear case its solution is a plane wave for which the dependence of the longitudinal wave number on the transverse number includes the term in the expansion which follows the parabolic term. It is shown that the field at a focal point is finite and the width of the beam does not exceed 1.1λ.