Optical nonlinearities of Fe2O3 nanoparticles investigated by Z-scan technique

The single beam Z-scan technique has been used to measure the third-order nonlinear refractive index, gamma, the two-photon absorption coefficient, beta, and the variation of refractive index per unit photoexcited carrier density sigma(r), and the free carrier absorption cross section sigma(ab) for quantum-confined Fe2O3 nanoparticles coated by a layer of organic molecular in toluene and bare particles in hydrosol. For coated Fe2O3 nanoparticles, the ratio gamma/beta is enhanced by a factor of five compared to the bare sample. Their figures of merit related to linear and two-photon absorption for ultrafast all-optical devices application were determined. (C) 1997 Elsevier Science B.V.