Plasmonic Core-Shell Nanowires for Enhanced Second-Harmonic Generation

We demonstrate the synthesis and characterization of core-shell nanowires consisting of a non-centrosymmetric KNbO3 core and a gold shell. This type of nanostructure combines the nonlinear optical properties of the core and the plasmonic resonance of the shell in the near infrared spectral range. We report successful spectroscopic measurements on coated single wires to characterize the resonant behavior of the gold shell. We present a theoretical model based on the electrostatic approximation to estimate the enhancement of second-harmonic generation in a nanowire due to the shell. It suggests a possible enhancement factor of up to 4,000 for a system with a nanoshell of 16 nm thickness at a wavelength of 900 nm.