Effects of backbone modification on the linear and third order nonlinear optical properties

Linear and third order nonlinear optical phenomena have been studied in two fluorene based copolymers having different polarisability. The materials synthesized and characterized show many of the properties necessary for device application. As a matter of fact they have been already used in the fabrication of both LED and FET. The complete linear and nonlinear optical characterization has been performed determining the real part of the refractive index n, its imaginary part k and the third order nonlinear value chi((3)). The higher third order nonlinear susceptibility on very homogeneous spin coated film has been measured in the more planar copolymer containing thiophene, showing a value of 2 x 10(-11) esu at 1650nm.