Third-order nonlinear optical properties of new dithienylethylenes

We report the measurement of the third-order susceptibilities of new dithie nylethylenes in solutions using the degenerate four wave mixing technique a t lambda = 532 nm in picosecond regime. From these measurements we deduced the values of second order hyperpolarizabilities gamma, which are about 10( 3) larger than the gamma value of CS2. We determined also the optical power limiting properties of the mentioned compounds. The measurements were made using nanosecond laser pulses in the visible range. The dispersion of nonl inear absorption coefficients is obtained in the framework of gaussian coll imated beam propagation in sample. (C) 2000 Elsevier Science S.A. All right s reserved.