Giant second harmonic generation by engineering of double plasmonic resonances at nanoscale

TL;DR

This paper demonstrates giant second harmonic generation in plasmonic core-shell nanocuboids by engineering double plasmonic resonances, significantly enhancing SHG efficiency for nanoscale light sources.

Contribution

It introduces a novel double-resonance nanostructure design that achieves over five orders of magnitude enhancement in SHG compared to non-resonant structures.

Findings

Giant SHG enhancement (>10^5 times) achieved with double plasmonic resonances.

Tuning aspect ratio aligns fundamental and SHG modes for optimal resonance.

Double-resonance structure improves energy trapping and transfer efficiency.

Abstract

We have investigated second harmonic generation (SHG) from Ag-coated LiNbO3 (LN) core-shell nanocuboids and found that giant SHG can occur via deliberately designed double plasmonic resonances. By controlling the aspect ratio, we can tune fundamental wave (FW) and SHG signal to match the longitudinal and transverse plasmonic modes simultaneously, and achieve giant enhancement of SHG by more than five orders of magnitude in comparison to a bare LN nanocuboid and by about one order of magnitude to the case adopting only single plasmonic resonance. The underlying key physics is that the double-resonance nanoparticle enables greatly enhanced trapping and harvesting of incident FW energy, efficient internal transfer of optical energy from FW to SHW, and much improved power to transport the SHG energy from the nanoparticle to the far-field region. The proposed double-resonance nanostructure can serve as an efficient subwavelength coherent light source through SHG and enable flexible engineering of light-matter interaction at nanoscale.