Raman Scattering near Metal Nanostructures

TL;DR

This paper investigates how metal nanostructures enhance Raman scattering in active media, revealing significant increases in conversion efficiency and the impact of local field effects on Raman gain at high intensities.

Contribution

It introduces a semi-classical model for Raman scattering near metal nanostructures, quantifies enhancement effects, and analyzes the influence of local field corrections on Raman gain.

Findings

Local field enhancement increases Raman conversion efficiency by 5-7 orders of magnitude.

Local field correction causes intensity-dependent frequency detuning.

High intensities can suppress Raman gain due to dynamic detuning.

Abstract

We study Raman scattering in active media placed in proximity of different types of metal nanostructures, at wavelengths that display either Fabry-Perot or plasmonic resonances, or a combination of both. We use a semi-classical approach to derive equations of motion for Stokes and anti-Stokes fields that arise from quantum fluctuations. Our calculations suggest that local field enhancement yields Stokes and anti-Stokes conversion efficiencies between five and seven orders of magnitudes larger compared to cases without the metal nanostructure. We also show that to first order in the linear susceptibility the local field correction induces a dynamic, intensity-dependent frequency detuning that at high intensities tends to quench Raman gain.