EFFECTIVE POLARIZABILITIES AND LOCAL-FIELD CORRECTIONS FOR NONLINEAR-OPTICAL EXPERIMENTS IN CONDENSED MEDIA

A consistent extension of Onsager's reaction field model to nonlinear- optical experiments in condensed media is presented. This model is use d to derive effective (nonresonant) linear and nonlinear molecular pol arizabilities involved in refractive index measurements, electric-fiel d induced second-harmonic generation, hyper-Rayleigh scattering, third -harmonic generation and degenerate four-wave mixing. The commonly app lied Lorentz correction, while being a useful approximation in linear optics, is demonstrated to lead to systematic errors of typically 20% in nonlinear optical experiments. This is due to an inherent inconsist ency that originates from the implicit assumption of a cavity held fac tor for the nonlinear molecular response. (C) 1998 American Institute of Physics. [S0021-9606(98)52003-X].