Effects of Order on Nonlinear Optical Processes in Organic Molecular Materials

Abstract

This paper establishes a general framework relating nonlinear optical processes to the molecular orientational order within the material. The orientational order is described as an ensemble average of orthogonal functions transforming from the molecular to the macroscopic frames using a distribution function appropriate for the particular material class. These molecular additivity concepts can be applied to many materials including crystals, liquid crystals, polymer liquid crystals, Langmuir-Blodgctt films, and polymer glasses. The literature is reviewed in the context of this description. Limitations, including inhomogeneity, defects, and quadrupole contributions are also discussed.