Reversible photo-switching of light-molecule coupling and chemical reaction modification in an optical microcavity

Organic photoswitches, molecules able to isomerize upon light irradiation, have applications in nano- and optoelectronics such as photoswitchable transistors, optical data storage, and sensors. Fulgide photoswitches are particularly attractive due to large spectral separation between their open and closed isomers and their ultrafast isomerization timescales. Here, we achieve strong light-matter coupling at room temperature by placing fulgides inside a Fabry Pérot cavity resonant with the closed isomer visible absorption. A large Rabi splitting is observed in reflection, indicating the emergence of hybrid polariton states. The coupling strength between molecules and photons can be reversibly and continuously tuned upon visible and UV irradiation, ranging from no coupling to strong coupling. Kinetics studies reveal the acceleration of photoisomerization in the strong coupling regime. Our results demonstrate tunable light-matter coupling strength as well as modification of a chemical reaction using all-optical control.