Electronic and nuclear contributions to the third-order nonlinear optical properties of new polyfluroalkysulfanyl-substituted tetrathiafulvalene derivatives

From DFWM efficiency measurements, we deduce third-order susceptibility of polyfluroalkylsulfanyl-substituted TTF derivatives. To know the physical nature of the optical non-linearities, we separate the electronic and nuclear contributions in chi ((3)). The electronic contribution of these molecules turned out dominant. We also deduce the values of the second-order hyperpolarisabilities gamma which are about 10(3) greater than the gamma value of CS2 at the same wavelength 532 nm As the absorption of the studied compounds is very weak at 532 nm, their merit factors in term of relation between the third-order susceptibility and linear absorption coefficient are better than the ones obtained for ethylenic TTF derivatives studied previously. (C) 2000 Elsevier Science S.A. All rights reserved.