Near-Field Enhancement of Optical Second Harmonic Generation in Hybrid Gold-Lithium Niobate Nanostructures

TL;DR

This paper demonstrates a significant enhancement of second harmonic generation in lithium niobate particles by coupling with gold nanoparticles, revealing a new approach to improve nonlinear optical device efficiency at the nanoscale.

Contribution

It introduces a novel near-field enhancement mechanism for second harmonic generation using gold nanoparticles coupled with lithium niobate, without the need for tailored nanoantennas.

Findings

Achieved approximately 32-fold increase in second harmonic generation.

Validated the enhancement mechanism through combined experimental and theoretical analysis.

Highlighted limitations of existing enhancement strategies and proposed a new near-field energy exchange approach.

Abstract

Nanophotonics research has focused recently on the ability of non-linear optical processes to mediate and transform optical signals in a myriad of novel devices, including optical modulators, transducers, color filters, photodetectors, photon sources, and ultrafast optical switches. The inherent weakness of optical nonlinearities at smaller scales has, however, hindered the realization of efficient miniaturized devices, and strategies for enhancing both device efficiencies and synthesis throughput via nanoengineering remain limited. Here, we demonstrate a novel mechanism by which second harmonic generation, a prototypical non-linear optical phenomenon, from individual lithium niobate particles can be significantly enhanced through nonradiative coupling to the localized surface plasmon resonances of embedded gold nanoparticles. A joint experimental and theoretical investigation of single mesoporous lithium niobate particles coated with aispersed layer of $\sim$10-nm diameter gold nanoparticles shows that a $\sim$32-fold enhancement of second harmonic generation can be achieved without introducing finely tailored radiative nanoantennas to mediate photon transfer to or from the non-linear material. This work highlights the limitations of current strategies for enhancing non-linear optical phenomena and proposes a route through which a new class of subwavelength nonlinear optical platforms can be designed to maximize non-linear efficiencies through near-field energy exchange.