NONLINEAR-OPTICAL SUSCEPTIBILITIES MEASURED IN POLY(PARA-PHENYLENE CUMULENE[3]) BY THE Z SCAN TECHNIQUE

Optical nonlinear susceptibilities were measured in Poly(paraphenylene cumulene[3]) (PPC) at 590nm and 1064nm. Both the real and imaginary parts of chi((3)) were evaluated with the Z scan technique using closed and open apertures, respectively. Open aperture Z scans on PPC at 590nm displayed a negative Im chi((3)), indicating saturation at this energy, as expected due to the close proximity to the absorption band edge. Due to accumulated long time effects, closed aperture scans gave erroneously high Re chi((3)) values and second hyperpolarizabilities of -3.9x10(-11)esu and -4.67x10(-28)esu, respectively.(1) The presence of a long time effect was verified by mechanically modulating the 1 kHz pulse train and observing radical changes in Re chi((3)) while peak and average powers remained constant.