Nonlinear Optical Susceptibilities Measured in Poly(Paraphenylene Cumulene[3]) by the Z Scan Technique

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Abstract
Optical nonlinear susceptibilities were measured in Poly(paraphenylene cumulene[3]) (PPC) at 590nm and 1064nm. Both the real and imaginary parts of χ(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 Imχ(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 Reχ(3) values and second hyperpolarizabilities of -3.9×10−11esu and -4.67×10−28esu, respectively.1 The presence of a long time effect was verified by mechanically modulating the 1 kHz pulse train and observing radical changes in Reχ(3) while peak and average powers remained constant.