ELECTROABSORPTION AND NONLINEAR OPTICAL-CONSTANTS OF TRANS-POLYACETYLENE AND POLY(3-HEXYLTHIOPHENE)

The authors present the results of electroabsorption measurements on thin films of trans-polyacetylene and poly(3-hexylthiophene). The induced changes in the absorption coefficient are quadratic in the applied electric field. The third order nonlinear susceptibility, χdc(3)(ω,o,o), and the change in the complex index of refraction are calculated via Kramers-Kronig analysis of the data. For trans-polyacetylene, a maximum value of the magnitude of χ(3) approx. 3×10MIN8 esu occurs near the band edge. χ(3) for poly(3-hexylthiophene) is about an order of magnitude smaller. The temperature and polarization dependence of the electroabsorption signal are also reported.