Enhancement of third-order optical nonlinearities by conjugated polymer-bonded carbon nanotubes

Third-order nonlinear susceptibility chi((3)) and second-order hyperpolarizability gamma of poly{[3-octylthiophene-2,5-diyl]-[p-aminobenzylidenequinomethane]-bonded multiwalled carbon nanotubes (POTABQ-MWNTs) were measured in chloroform solution using degenerate four-wave mixing at 532 nm under nanosecond pulse excitation. Effective nonlinear absorption coefficient beta(eff) and nonlinear refraction index n(2) were obtained using open aperture and close aperture Z-scan technique at the same wavelength, respectively. Optical limiting property of the sample was also investigated. The resulting POTABQ-MWNTs exhibited large third-order nonlinear optical responses mainly due to the formation of intramolecular photoinduced charge-transfer system of polymers and carbon nanotubes. (c) 2005 American Institute of Physics.