Third-order Nonlinear Optical Properties of Ethylenic Tetrathiafulvalene Derivatives

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Abstract
The degenerate four-wave-mixing method is used to measure the second-order hyperpolarizabilities γ of new soluble tetrathiafulvalene (TTF) derivatives. For each material, the study of solutions at various concentrations leads to the choice of an optimum solution: a compromise between ‘low-nonlinearity low-loss’ and ‘high-nonlinearity high-loss’ solutions and thus to the determination of its susceptibility χ3. The hyperpolarizabilities are deduced from these measurements; ethylenic TTF derivatives show γelectronic values as large as −7·58 × 10−45 (MKS), larger than acetylenic TTF derivatives which have γelectronic = −1·12 × 10−45.