Photoinduced 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 [ Hutchison et al. Adv. Mater. 2013, 25, 2481-2485 ], chemical reactivity [ Hutchison et al. Angew. Chem., Int. Ed. 2012, 51, 1592-1596 ], ultrafast energy relaxation [ Salomon et al. Angew. Chem., Int. Ed. 2009, 48, 8748-8751; Gomez et al. J. Phys. Chem. B 2013, 117, 4340-4346 ], and electrical conductivity [ Orgiu et al. Nat. Mater. 2015, 14, 1123-1129 ] 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 localized plasmon resonances on metal nanowires modifies the efficiency of the photoinduced charge-transfer rate of plasmonic derived (hot) electrons into accepting states in the semiconductor material. Ultrafast 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.