The second hyperpolarizabilities of three heterocyclic molecules of C4H4X, where X = O (furan), S (thiophene), or Se (selenophene), were investigated by an optical-heterodyne-detected optical-Kerr-effect experiment and an ab initio Hartree–Fock molecular orbital calculation with largely augmented basis sets. From the observed third-order responses the electronic hyperpolarizabilities were determined after the nuclear nonlinear optical responses were removed by Fourier-transform analysis. Results of both experiment and calculation exhibited ~2 times enhancement when the heteroatom of O was replaced by Se. The origin of the enhancement and the contribution of the heteroatom to the hyperpolarizability are discussed. Also, a direct comparison of the experimental values with calculated ones is made.
© 1998 Optical Society of America
(000.5360) General : Physics literature and publications
(070.2590) Fourier optics and signal processing : ABCD transforms
(190.0190) Nonlinear optics : Nonlinear optics
(190.3270) Nonlinear optics : Kerr effect
(320.7100) Ultrafast optics : Ultrafast measurements
Kenji Kamada, Minoru Ueda, Toru Sakaguchi, Koji Ohta, and Toshio Fukumi, "Heavy-atom effect on second hyperpolarizabilities of thiophene homologues investigated by a femtosecond optical-Kerr-effect experiment and ab initio molecular orbital calculation," J. Opt. Soc. Am. B 15, 838-845 (1998)