General questions of the theory of second harmonic generation of laser radiation in uniaxial crystals are discussed. Derivation of integral equations is suggested, which determine the type of interacting fields in an observation plane situated behind a crystal at an arbitrary distance. It is suggested to solve these equations with boundary conditions specified on the same observation plane. It is shown that such unusual choice of the plane of boundary conditions definition at an assumed field approximation allows an essential simplification of a required representation for the second harmonic field.
second harmonic generation, uniaxial crystal, nonlinear wave equation