Nonlinear optical responses of nanoparticle-polymer composites incorporating organic (hyperbranched polymer)-metallic nanoparticle complex

We report on experimental studies of the nonlinear optical properties of nanocomposites consisting of organic (hyperbranched polymer)-metallic (Au or Pt) nanoparticle complex embedded in polymer films. Open-aperture and closed-aperture z-scan techniques are used to measure the effective third-order nonlinear optical susceptibilities chi((3))(eff) of the composites under picosecond laser radiation at a wavelength of 532 nm. The relative sign of the real and imaginary parts of chi((3))(eff) could be explained qualitatively by the Kramers-Kronig relation. We also determined the third-order nonlinear optical susceptibilities of Au and Pt nanoparticles estimated from the measured values for chi((3))(eff) to be (-5.48+4.76i) x 10(-8) esu and (4.41-0.65i) x 10(-6) esu, respectively, at 532 nm with a help of the Maxwell-Garnett model. (C) 2010 American Institute of Physics. [doi:10.1063/1.3489996]