2PA induced optical limiting behaviour of metal (Ni, Cu, Zn) niobate decorated reduced graphene oxide

Abstract

Nanopulsed Nd:YAG green laser induced nonlinear absorption and optical limiting properties of metal niobate decorated reduced graphene oxide were studied by single beam Z-scan experiment. Initially reduced graphene oxide was decorated with metal niobates MNb2O6 (with M = Ni/Cu/Zn) using one-step hydrothermal method. Formation of stable orthorhombic (nickel, copper and zinc) niobate by annealing at different temperatures (950 °C, 850 °C and 900 °C) and metal niobate/rGO composites was confirmed through XRD and Raman studies. SEM with EDS exposed the incorporation of inorganic species and agglomerated spherical metal niobate morphologies upon graphene layers. The absorption band edge of pure metal niobate was observed around 320 nm (ZnNb2O6) and it was blue shifted to 300 nm in metal niobate:rGO composite (ZnNb2O6:rGO). Open aperture Z-scan pattern ascertained the presence of reverse saturable absorption (RSA) ascribed due to genuine two-photon (2 PA) absorption process. Metal niobate decorated rGO possess high 2 PA coefficient (1.42 × 10−10 m/W) and onset optical limiting threshold (1.05 × 1013 W/m2) than pure metal niobates and rGO. Among the samples, ZnNb2O6: rGO showed stronger nonlinear absorption and optical limiting performance than its counterparts and other known OL materials like GO, Au: GO, C60 etc., excited under similar excitation conditions. The obtained result consolidates that enhanced OL action of metal niobate decorated rGO find potential application in laser safety devices and energy stabilizer in most widely used 532 nm, 9ns laser domain.