Nanocavity-enhanced fluorescence and Raman scattering

Abstract

Our aim is to study light-matter interaction in the deep subwavelength regime where electromagnetic radiation is confined by localized surface plasmon resonances (LSPRs).The high field enhancement and increased local density of states (LDOS) are mainly responsible for boosting the signal strength (such as the Raman and fluorescence) from molecules present in plasmonic nanogaps. We leverage self assembled plasmonic nanocavites (such as nano-dimers and nanoparticles-on-mirror) to reach single molecule sensitivity.
 
While the molecular signatures are of great interest, we also study some fundamental aspects concerning the plasmonic nanocavities themselves. Such as the stability of molecular monolayers in the gap [1], formation of nanoscale domains acting as confined quantum emitters [2] as well as the controlled coupling of light into various LSPR modes of the plasmonic nanocavity [3].
 
We study single molecules within these plasmonic nanocavities through stochastic events such as picocavities or by deterministically localizing single molecules in the hotspot using DNA origami based nanotechnology. The latter has allowed us to measure the Purcell broadening and Lamb shifts of a single fluorophore. Engineering the plasmonic nanocavity also enables cavity mediated fluorescence far-detuned from the emitter’s intrinsic zero-phonon line (ZPL) [4].
 
The design, electromagnetic simulation, fabrication and characterization of single nanocavities are crucial to unravel the intricate near-field dynamics governing deeply subwavelength photonic systems. We are constantly looking to improve our optical setups and simulation methods while pushing our nanofabrication capabilities towards synthesizing hybrid nanophotonic devices, integrating metallic nano-clusters, cucurbiturils as well as 2D heterostructures.