Synthesis and Largely Enhanced Nonlinear Refraction of Au@Cu2O Core-Shell Nanorods

Abstract

Au@Cu2O core-shell nanorods with tunable thickness of Cu2O shell were synthesized and their linear and nonlinear optical responses were investigated. Two transverse plasmon resonance peaks were observed when the Au nanorods were coated with Cu2O shells, which were adjusted by the Cu2O shell thickness. The nonlinear absorption of the Au@Cu2O nanorods is enhanced by 5 times at the longitudinal plasmon resonance wavelength compared with that of bare Au nanorods. More intriguingly, largely enhanced nonlinear refraction and suppressed nonlinear absorption at the transverse plasmon resonance wavelength were observed in the Au@Cu2O nanorods. Our findings indicate the existence of strong local field enhancement at the interface between the Au core and the Cu2O shell, which would provide a promising strategy in designing plasmonic nonlinear nanodevices with good nonlinear figures of merit.