Core-shell potassium niobate nanowires for enhanced nonlinear optical effects

Area of Science:

• Nanomaterials Science
• Optoelectronics
• Surface Chemistry

Background:

• Core-shell nanostructures offer unique optical properties by combining material functionalities.
• Potassium niobate (KNbO3) exhibits significant nonlinear optical properties.
• Gold shells provide plasmonic resonance, enhancing light-matter interactions.

Purpose of the Study:

• To synthesize and optically characterize KNbO3/Au core-shell nanowires.
• To investigate the influence of surface functionalization on nanostructure quality and optical performance.
• To model and understand the enhanced second-harmonic generation (SHG) signal.

Main Methods:

• Synthesis of KNbO3 nanowires followed by gold shell deposition.
• Comparison of silanization and polyelectrolyte functionalization methods.
• Optical characterization including spectroscopy and nonlinear optical measurements.
• Mie-theory based modeling of optical properties.

Main Results:

• Polyelectrolyte functionalization resulted in smoother, more complete core-shell structures.
• A strong localized surface plasmon resonance was observed near 900 nm.
• A 250-fold enhancement in the second-harmonic generated (SHG) signal was measured compared to uncoated nanowires.
• Simulations indicated optimal dimensions of 35 nm wire radius and 7.5 nm shell thickness.

Conclusions:

• KNbO3/Au core-shell nanowires effectively combine nonlinear optical and plasmonic properties for enhanced optical signals.
• Polyelectrolyte functionalization is a preferred method for synthesizing high-quality core-shell nanostructures.
• The discrepancy between measured and calculated enhancement is attributed to the roughness of the gold shell.