ABSTRACT
This chapter presents some ideas regarding methods for calculating the nonlinear optical susceptibility that differ from the standard approach commonly used by most workers. However, because these approaches lie outside of conventional methods, they provide different insights into the nature of the nonlinear optical susceptibility, and perhaps can provide increased understanding of the nature of nonlinear optical interactions. The atomic response is then calculated by finding how the state of the system is modified by the applied field. The validity of Miller’s rule is well established for a variety of second-order nonlinear optical materials. Time-dependent, quantum mechanical perturbation theory is used. Wang’s rule can be used to derive a well known empirical relationship that allows one to predict the nonlinear refractive index of a material from measurements of linear optical properties.
