Dispersion of degenerate four-wave mixing (DFWM) efficiency near the exciton resonance
of aggregates of 1,1′-diethy1-2-2′-cyanine (pseudoisocyanine, PIC) chloride is reported.
Correlation with the spectrum of imaginary parts of nonlinearity obtained by pump and
probe techniques is discussed. Third order nonlinear susceptibility of PIC aggregates
has been calculated supposing highest density packing attainable by Langmuir-Blodgett
technique. The nonlinear figure-of-merit of aggregates was evaluated, which is intensity
dependent due to exciton annihilation. Observed intensity and wavelength dependence
of mixing efficiency is qualitatively explained in terms of absorption saturation, exciton
annihilation, and subsequent generation of an excess diagonal disorder by vibrational
energy accumulated in aggregates.
Copyright
Copyright © 1997 Hindawi Publishing Corporation. This is an open access article distributed under the
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