Abstract

Only noncentrosymmetric molecules can possess a second-order nonlinear response, i.e., they have a nonvanishing first molecular hyperpolarizability. Polar molecules with donor and acceptor groups connected by a conjugated π electron system are traditional organic second-order materials. For macroscopic noncentrosymmetry, such molecules are incorporated in, e.g., a polymer host and poled with a static electric field. The nonlinear coefficients of poled materials are proportional to the product μβ where p is the permanent dipole moment of the molecules and β is the vectorial part of the first hyperpolarizability [1].

© 1996 Optical Society of America