By the use of sum rules, the largest third-order molecular nonlinear-optical susceptibilities allowed by quantum mechanics are determined. The theoretical upper limit is found to depend only on the first excited-state transition energy and on the number of electrons, in agreement with experimental data.
© 2000 Optical Society of America
Mark G. Kuzyk, "Fundamental limits on third-order molecular susceptibilities," Opt. Lett. 25, 1183-1185 (2000)