Large refractive nonlinearities and two-photon absorption in aryl-substituted dithiolenes

We have investigated some aryl substituted dithiolenes which show enhanced nonlinearity and their incorporation into polymer films. These neutral molecules show strong near infra-red absorption whose position is determined primarily by the extent of electron delocalization and the metal atom to which the sulphur ligands are attached. The presence of electron donating groups bathochromically shifts the band and selective detuning from the band is possible to arrive at optimum values for the important ration of nonlinear susceptibility to linear absorption, (chi) (3 )/(alpha) . Nonlinear optical characterization of these materials by degenerate four wave mixing and z-scan is described.