Novel nonlinear optical organic materials:: Dithienylethylenes

In this paper, we report the measurements of the third-order susceptibilities of new dithienylethylenes in solutions using the degenerate four-wave mixing technique at lambda =532 nm in the picosecond regime. From these measurements we deduced the second-order hyperpolarizabilities gamma values, which are about 10(3) larger than the gamma value of CS2 and are comparable with the corresponding values for the new synthesized diphenylpolyene derivatives. We also determined the optical power limiting properties of the mentioned compounds using nanosecond laser pulses in the visible range. The dispersion of nonlinear absorption coefficients is obtained in the framework of Gaussian collimated beam propagation in sample. Kerr ellipsometry measurements are responsible for the excited absorption cross section and are spectrally shifted comparing with the optical limiting processes (up to 50 nm). The appropriate quantum chemical calculations are done. The contributions of electronic and vibration subsystems as well as contribution of the particular parts of each molecule into the output third nonlinear optical response are given. (C) 2001 American Institute of Physics.