Degenerate four-wave mixing measurements of the chi((3)) non-linear optical properties of poly(arylene-ethynylenesilylene)s

The third-order optical non-linearity in solution of a series of poly(aryle ne-ethynylenesilylene)s containing a variety of backbone arylene groups and substituents at silicon has been studied by using the degenerate four-wave mixing technique at 1064 nm with a 6 ns pulse duration. Thermal grating ef fects may be neglected under the experimental set-ups employed, The results obtained are greater by more than two orders of magnitude than those previ ously measured for some of the polymers using the Z-scan technique at the s ame wavelength. The electronic contribution to the fast non-linearity is gr eater than the nuclear (orientational) contribution by a factor of at least 4. The presence of a single 8-(dimethylamino)naphthyl ligand at silicon af fording pentacoordination has a beneficial effect on the chi((3)) propertie s. The high chi((3)) properties of the polymers (e.g. \Re chi((3))\ = 9.5 x 10(-12) esu for [-C=C-SiPh2-C=C - (1,4 - C6H4)-](n) in chloroform [5 g l(- 1)]) confirm the presence of extensive through-Si conjugation along the bac kbone. Copyright (C) 2000 John Wiley & Sons, Ltd.