Abstract
We show that quadratic electroabsorption (QEA) can be used for measurement of the hyperpolarizability β in asymmetric, polar molecules. QEA has already been used to obtain the second hyperpolarizability γ in centrosymmetric molecules. However, because of the existence of a static dipole moment μ in asymmetric molecules, β can contribute significantly to the third-order susceptibility measured with the QEA experiment owing to a reorientational mechanism through the mixed term βμ. We apply inhomogeneously broadened, quantum sum-over-states models for both β and γ to describe the QEA response of asymmetric molecules. Comparing the models and the data for two asymmetric nonlinear optical chromophores, we found that β yields the dominant response. QEA is thus a useful tool for measuring the dispersion of β and can be used for reliable determination of the off-resonant value
© 2005 Optical Society of America
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