Photo-induced electron transfer in the strong coupling regime: Waveguide-plasmon polaritons

Reversible exchange of photons between a material and an optical cavity can lead to the formation of hybrid light–matter states where material properties such as the work function\cite{Hutchison_AM2013a}, chemical reactivity\cite{Hutchison_ACIE2012a}, ultra–fast energy relaxation \cite{Salomon_ACIE2009a,Gomez_TJOPCB2012a} and electrical conductivity\cite{Orgiu_NM2015a} of matter differ significantly to those of the same material in the absence of strong interactions with the electromagnetic fields. Here we show that strong light–matter coupling between confined photons on a semiconductor waveguide and localised plasmon resonances on metal nanowires modifies the efficiency of the photo–induced charge–transfer rate of plasmonic derived (hot) electrons into accepting states in the semiconductor material. Ultra–fast spectroscopy measurements reveal a strong correlation between the amplitude of the transient signals, attributed to electrons residing in the semiconductor, and the hybridization of waveguide and plasmon excitations.