Nonlinear optical spectroscopy on one-dimensional excitons in silicon polymer, polysilane

The modulus and phase of the complex third-order nonlinear optical (NLO) susceptibility χ${\mathrm{̃}}^{\mathrm{}\left(3\right)\mathrm{}}$(-3ω;ω,ω,ω) have been measured on an all-trans silicon polymer, poly(dihexylsilane), over a wide photon energy range. Several distinct structures observed in the χ${\mathrm{̃}}^{\mathrm{}\left(3\right)\mathrm{}}$ spectra are in excellent agreement with the theoretical results of a one-dimensional (1D) exciton model. Important aspects of the 1D Wannier-like exciton structure in polysilanes are elucidated in relation to the NLO processes.