Dongxiang Zhang

Large third-order optical nonlinearity of periodic gold nanoparticle arrays coated with ZnO

The third-order optical nonlinearity of a composite film consisting of periodic triangular gold nanoparticle arrays coated with ZnO was investigated by the z-scan technique. The third-order nonlinear susceptibility, ?(3), measured at a wavelength of 532?nm with a pulse duration of 10?ns, was up to 1.3 ? 10?5?esu. The figure of merit, ?3/? (where ? is the absorption coefficient) was about 1.1 ? 10?9?esu?cm. The large optical nonlinearity is likely due to the strong local electromagnetic field near the triangular gold particles and ZnO matrix. The results show that the composite film has great potential for nonlinear optical devices.

Third-order optical nonlinearity of gold nanoparticle arrays embedded in a BaTiO 3 matrix

Au:BaTiO(3) composite films comprising hexagon-shaped Au nanoparticle arrays covered with BaTiO(3) matrix were fabricated by double-layer nanosphere lithography and pulsed laser deposition technique. The optical nonlinearity of the composite film was determined using the Z-scan technique at a wavelength of 532 nm and a pulse duration of 25 ps. The third-order nonlinear optical susceptibility, chi(3), was found to be 2.9x10(-8) esu, which is comparable with the best values in metal-dielectric films comprising randomly distributed spherical particles but with much higher metal concentrations. The local electric field enhancement in and near the particles was investigated using the dipole discrete approximation method.

Large optical nonlinearity of Au nanoparticle-dispersed Ba0.6Sr0.4TiO3 films prepared by pulsed laser deposition

Crystallized Au nanoparticle-dispersed Ba0.6Sr0.4TiO3 (Au : BST) thin films were prepared on MgO (1 0 0) substrates by pulsed laser deposition. The peak of the linear absorption coefficient for the film shifts to longer wavelength with an increase in Au concentration. Among all the tested samples, the largest values of third-order nonlinear susceptibility were calculated to be −1.93 × 10−6 esu and 1.13 × 10−5 esu corresponding to imaginary and real parts, respectively, which were determined by a single beam Z-scan at a wavelength of 532 nm with a laser duration of 10 ns. The relationship between Au concentration and third-order nonlinear susceptibility was also analysed.

Enhanced femtosecond optical nonlinearity of Mn doped Ba0.6Sr0.4TiO3 films

We report the third-order optical nonlinearity of ferroelectric thin films of Mn doped Ba0.6Sr0.4TiO3 using Z-scan measurement with femtosecond laser pulses at 800 nm. The nonlinear refraction index and two-photon absorption coefficient are measured to be 3.0×10−4u2002cm2/GW and 1.7 cm/GW, respectively, which are about one order of magnitude larger than those of the undoped Ba0.6Sr0.4TiO3 thin films. The enhancement is attributed to the acceptor behavior of Mn ions dopant. The figure of merit, T, defined by T=βλ/n2, was calculated to be 0.44, less than 1. The results indicate that the thin films have great potential applications in nonlinear photonic devices.