Hybrid cavity-antenna architecture for strong and tunable sideband-selective molecular Raman scattering enhancement

TL;DR

This paper introduces a hybrid cavity-antenna system that combines plasmonic nanocubes with a tunable microcavity to achieve selective, strong Raman scattering enhancement and spectral control for molecular vibrations.

Contribution

It presents an experimental platform that hybridizes plasmonic antennas with a tunable cavity, enabling spectral selectivity and enhanced Raman scattering beyond traditional plasmonics.

Findings

Hybrid system achieves narrow optical modes with strong Raman enhancement.

Theoretical and experimental analysis confirms effective mode hybridization.

Potential for dynamical back action effects in molecular optomechanics.

Abstract

Plasmon resonances at the surface of plasmonic antennas allow for extremely strong enhancement of Raman scattering. Intrinsic to plasmonics, however, is that extreme field confinement lacks precise spectral control, which would hold great promise in shaping the optomechanical interaction between light and molecular vibrations at will. We demonstrate an experimental platform composed of a plasmonic nanocube-on-mirror antenna coupled to an open, tunable Fabry-Perot microcavity for selective addressing of individual vibrational lines of molecules with strong Raman scattering enhancement. Multiple narrow and intense optical resonances arising from the hybridization of the cavity modes and the plasmonic broad resonance are used to simultaneously enhance the laser pump and the local density of optical states (LDOS) and are characterized using rigorous modal analysis. The versatile bottom-up fabrication approach permits quantitative comparison with the bare nanocube-on-mirror system, both theoretically and experimentally. This shows that the hybrid system allows for similar SERS enhancement ratios with narrow optical modes, paving the way for dynamical back action effects in molecular optomechanics.