“Quadrupoling” for Second Order Nonlinear Optics

Abstract

Achieving noncentrosymmetric order for second-order nonlinear optical materials has been a continuing focus of research. Monomolecular layer deposition and electric field poling of polymers have been favored approaches to generating noncentrosymmetric polymeric and organic materials.1 In this case, the alignment exploits the vector part of the molecular hyperpolarizability tensor which is optimized in donor and acceptor substituted conjugated molecules. The principles behind the nonlinearities, both molecular and macroscopic are well-known, and considerable work has been directed at optimizing them. More recently, it has been pointed out that the octupolar hyperpolarizability component is ubiquitous and can be as large or larger than the vector part with appropriate molecular design.2