DETERMINATION OF REAL AND IMAGINARY PART OF CHI((3)) OF THIOPHENE OLIGOMERS USING THE Z-SCAN TECHNIQUE

Using the single beam z-scan technique with 30 ps pulses at 532 nm (cl ose to the linear absorption region) the values of real and imaginary part of third-order optical nonlinear susceptibility chi((3)) in solut ions of thiophene oligomers have been determined for different numbers of repeat units (n = 2-6). The values of the real part of chi((3)) we re found to be negative, the contribution of each repeat unit to this value increases with increasing chain length. In solutions of dioxane (10(-3) mol/l) we measured n(2) values in the order of 10(-13) esu, wh ereas two-photon absorption coefficients of about 0.1 cm/GW were found .