Novel nonlinear optical organic materials: Dithienylethylenes

In this paper, we report the measurements of the third-order susceptibiliti es of new dithienylethylenes in solutions using the degenerate four-wave mi xing technique at lambda =532 nm in the picosecond regime. From these measu rements we deduced the second-order hyperpolarizabilities gamma values, whi ch are about 10(3) larger than the gamma value of CS2 and are comparable wi th the corresponding values for the new synthesized diphenylpolyene derivat ives. We also determined the optical power limiting properties of the menti oned compounds using nanosecond laser pulses in the visible range. The disp ersion of nonlinear absorption coefficients is obtained in the framework of Gaussian collimated beam propagation in sample. Kerr ellipsometry measurem ents are responsible for the excited absorption cross section and are spect rally shifted comparing with the optical limiting processes (up to 50 nm). The appropriate quantum chemical calculations are done. The contributions o f electronic and vibration subsystems as well as contribution of the partic ular parts of each molecule into the output third nonlinear optical respons e are given. (C) 2001 American Institute of Physics.