Two-photon absorption in quantum dots based on a nonconjugated conductive polymer

Two-photon absorption has been measured in a nano-optical material (quantum dots) based on the nonconjugated conductive polymer, iodine-doped poly(beta-pinene). The measurement has been made using open-aperture z scan at 730-860 nm with 150 fs pulses. Exceptionally large two-photon absorption coefficient has been observed with a peak of magnitude similar to 2.6 cm/MW that appeared at similar to 1.53 eV which is close to half of the optical gap corresponding to the charge-transfer transition involving the isolated double bond. Saturation of absorption was observed at lower intensities and shorter wavelengths. The results have been attributed to the quantum dots (subnanometer size) formed upon doping. (c) 2007 American Institute of Physics.