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Molecular structure and its relation to optical limiting

We report on the correlation between features of the molecular structure of polyphenyls and the measured parameters of optical limiting: limiting threshold and clamped output. Optical limiting in these materials is mainly due to a strong light scattering (third order negative nonlinear effect). We show that in many simple cases the limiting threshold decreases with increased conjugation length, linearity, planarity and with the substitution of acceptor/donor end groups. The UV spectra and the wavelength dependence of the limiting parameters suggests that a two photon absorption mechanism is necessary for a low threshold and efficient light scattering.