EPSRC CDT in Metamaterials: Advancing single molecule detection with strong light-matter interactions on plasmonic nanostructures

The studentship is part of the EPSRC Centre of Doctoral Training in Metamaterials (XM2). Its aim is to undertake world-leading research, while training scientists and engineers with the relevant research skills and knowledge, and professional attributes for industry and academia.

Ultra-sensitive biodetection has been demonstrated with plasmon resonances excited in gold nanoparticles. Electromagnetic fields enhance and localize in ‘hotspots’ at the nanoparticle sensor. When biomolecules attach within these hotspots, large resonance frequency shifts are observed. The field enhancements furthermore enable the observation of optical phenomena that depend on the high field intensities. Examples for this are surface enhanced Raman effects, surface enhanced fluorescence, surface enhanced infra-red absorption, etc.


Recently, it has been shown that optical microcavities enable a sensitive read-out of the optical response of plasmonic nanoparticles. This is particularly interesting for biosensing. The combination of nanoparticles with so called whispering gallery modes (WGM) has resulted in unprecedented sensitivity levels for label-free detection of single molecules [1]. These hybrid WGM sensors are expected to advance even further by exploiting optical phenomena that require the high near field intensities combined with the high Q factor of WGMs.

To this end, we will study the advancements of hybrid WGM sensors by strong coupling between photonic-plasmonic microcavities and emitters. Strong coupling will result in the observation of important physical phenomena such as Rabi splitting, and can enable the engineering of electronic energy levels [2] which is relevant to chemical sensing. In addition, the strong coupling to plasmon resonances in metamaterials can provide for unique detection modalities, such as a differential WGM response to chiral nanoparticles and molecules.

[1] M. D. Baaske, M. R. Foreman and F. Vollmer, "Single-molecule nucleic acid interactions monitored on a label-free microcavity biosensor platform" Nature Nanotechnology 9, 933–939 (2014)

[2] P. Törmä and W. L. Barnes, “Strong coupling between surface plasmon polaritons and emitters: a review” Rep. Prog. Phys. 78, 013901 (2015)