The first hyperpolarizabilities (β) of donor–acceptor-substituted push–pull molecules are generally described by a model in which the lowest excited electronic state dominates the optical response. It is shown that within the usual assumptions accompanying this two-state model, β(−2ω; ω, ω) can be expressed in terms of a Kramers–Kronig transform of the linear optical absorption spectrum. The method is applied to <i>p</i>–nitroaniline and several other push–pull chromophores, and results are compared with experimental data where available. Comparison of calculated and measured frequency dispersions is suggested as a purely experimental method, requiring no additional parameters, to test the assumptions of the two-state model.
© 2002 Optical Society of America
(160.4330) Materials : Nonlinear optical materials
(160.4890) Materials : Organic materials
(190.4400) Nonlinear optics : Nonlinear optics, materials
(190.4710) Nonlinear optics : Optical nonlinearities in organic materials
(300.6420) Spectroscopy : Spectroscopy, nonlinear
Anne Myers Kelley, "Frequency-dependent first hyperpolarizabilities from linear absorption spectra," J. Opt. Soc. Am. B 19, 1890-1900 (2002)