Third-order nonlinear optical properties of a soluble conjugated polythiophene derivative

The second hyperpolarizability 〈γxxxx 〉 of a new, soluble, conjugated polythiophene derivative, containing aromatic and quinoid moieties, is measured to be 1.2×10−31 esu. The measurement was made at 532 nm in a dichloromethane solution by picosecond-resolved degenerate four wave mixing. The corresponding macroscopic third-order susceptibility χ(3 ) is estimated to be 4.6×10−9 esu, which is larger than that of the parent poly(2,5-thiophene) and many currently known nonlinear optical polymers.