Abnormal nonlinear optical properties of hybrid graphene-TiO2 nanostructures.

Abstract

The nonlinear optical (NLO) properties of graphene-TiO2 nanoparticle (GNP) composite and graphene-TiO2 nanowire composite (GNW) are investigated by spatial self-phase modulation (SSPM) and Z-scan. The SSPM results of the GNP and GNW show that they possess strong self-diffraction effects at 1100nm and no signal at 700nm, which is different from all previous reports of other two-dimensional materials. A possible mechanism is that NLO behaviors are dominated by TiO2 at the visible wavelength, while by graphene at a near-infrared wavelength. The Z-scan results of the GNP and GNW show reverse saturable absorption (RSA) at 700nm, but saturable absorption (SA) at 1100nm. Our results demonstrate that, by choosing appropriate coupling, we could design two-dimensional materials that have specific NLO properties at particular wavelengths.