Prediction of third‐order nlo properties of organic molecules

Organic materials with large nonlinear optical (NLO) responses will be important in the development of photonic technology. In the search for such materials, the ability topredict the NLO responses of molecules will be invaluable. Techniques for the computation of the second‐order hyperpolarizability γ aredescribed, including molecularorbitalk models, semiempirical nethods, andab initio methods, The effects of structure on γ are discussed, together withthe remarkablelresult that in three classes of simple compounds γ can be linearly correlated with molecular mass, regardless of the polarity of the compounds.