Optical third-harmonic generation in polyacetylene.

Third-harmonic generation experiments have been performed on fully oriented crystalline ItransR-(CH${)}_{\mathrm{x}}$ Rat two laser wavelengths: 1.064 and 1.907 \ensuremath{\mu}m. Theoretical analysis of third-harmonic generation in a semiconductor slab is presented which allows the extraction of the electronic third-order susceptibility from the experiments. A simple method was used for the elimination of environmental effects on the measurements. The third-order susceptibilities obtained are \ensuremath{\Vert}${\ensuremath{\chi}}_{\mathrm{xxxx}}^{(3)}$(\ensuremath{\omega},\ensuremath{\omega},\ensuremath{\omega}) ${\mathrm{\ensuremath{\Vert}}}_{\ensuremath{\lambda}=1.064\phantom{\rule{0ex}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{m}}$=(9\ifmmode\pm\else\textpm\fi{}4) \ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}9}$ esu and \ensuremath{\Vert}${\ensuremath{\chi}}_{\mathrm{xxxx}}^{(3)}$(\ensuremath{\omega},\ensuremath{\omega},\ensuremath{\omega}) ${\mathrm{\ensuremath{\Vert}}}_{\ensuremath{\lambda}=1.907\phantom{\rule{0ex}{0ex}}\mathrm{\ensuremath{\mu}}\mathrm{m}}$ =(1.7\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}8}$ esu, representing exceptionally high values compared to other organic and inorganic semiconductors.