Enhancement of ultrafast nonlinear optical response of zinc selenide nanoparticle decorated reduced graphene oxide sheets

Abstract

The synergistic effect of zinc selenide (ZnSe) nanoparticle functionalized into reduced graphene oxide (RGO) sheets on nonlinear optical (NLO) properties has been investigated by single beam z-scan technique. Comprehensive measurements on nonlinear absorption (NLA) as well as nonlinear refraction (NLR) have been performed on RGO, ZnSe, and RGO-ZnSe composites at 630 nm in the femtosecond regime. Both NLA and NLR of RGO-ZnSe show an enhancement in NLO properties compared to pure RGO and ZnSe in an intensity range of 37GW/cm2 to 130GW/cm2. The enhanced optical nonlinearity of RGO-ZnSe may have been caused due to strong interlayer coupling between RGO and ZnSe, as well as the availability of a large number of NLA states in the composite. The interlayer coupling between ZnSe nanoparticles and RGO sheets has been confirmed by transmission electron microscopy, UV-Visible, and photoluminescence spectroscopy. At low input pulse intensity (∼37GW/cm2), saturation absorption dominates, whereas NLA becomes prominent in the higher intensity regime (55GW/cm2–130GW/cm2) for RGO and ZnSe. NLA is the dominant phenomenon for RGO-ZnSe in the whole experimental intensity range. Moreover, it is observed that the dispersion of RGO, ZnSe, and RGO-ZnSe in dimethylformamide exhibits positive NLR. This study indicates an enhancement in nonlinear optical response of the RGO-semiconductor composite, which is very promising for graphene based photonic device applications.