Spontaneous and Stimulated Raman Scattering near Metal Nanostructures in the Ultrafast, High-Intensity regime

TL;DR

This paper investigates how atomic inversion influences Raman scattering near metal nanostructures under ultrafast, high-intensity conditions, revealing phenomena like population inversion, gain saturation, and a switch-like transition to stimulated Raman scattering.

Contribution

It demonstrates that accounting for atomic inversion dynamics is crucial in plasmonic Raman scattering under ultrafast, high-intensity regimes, a factor often neglected in prior studies.

Findings

Population inversion occurs within hot spots.

Gain saturation is observed at high intensities.

A switch-like transition to stimulated Raman scattering spans twelve orders of magnitude.

Abstract

The inclusion of atomic inversion in Raman scattering can significantly alter field dynamics in plasmonic settings. Our calculations show that large local fields and femtosecond pulses combine to yield: (i) population inversion within hot spots; (ii) gain saturation; and (iii) conversion efficiencies characterized by a switch-like transition to the stimulated regime that spans twelve orders of magnitude. While in Raman scattering atomic inversion is usually neglected, we demonstrate that in some circumstances full accounting of the dynamics of the Bloch vector is required.