Nonlinear optical spectroscopy on polysilanes: Dependence of exciton states on polymer backbone conformations

The third-order nonlinear optical (NLO) susceptibility χ(3)(-3ω;ω,ω,ω) have been measured on spin-coated films of three kinds of polysilanes (PSʹs) with various backbone conformations, in a wide range of fundamental wavelength, by means of third-harmonic generation (THG) measurement. The experimental results show that their quasi-one-dimensional (Q1D) exciton level structures and their optical nonlinearity systematically change, with their backbone conformation changes. As compared with the theoretical calculation by 1D exciton model, the experimental feature indicates that the on-site electron correlation takes important roles in Q1D exciton states of PSʹs.