Ultrafast polariton relaxation dynamics in an organic semiconductor microcavity
T. Virgili, S. K. Rajendran, D. Brida, D. Polli, G. Cerullo
IFN, CNR Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy
D. Coles, A. M. Adawi, D. G. Lidzey
Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom
Helia Photonics Ltd. Rosebank Park, Livingston, West Lothian EH54 7EJ, United Kingdom
Institute of Theoretical Physics and Astrophysics, University of Würzburg, D-97074 Würzburg, Germany
We study an organic semiconductor microcavity operating in the strong-coupling regime using fs pump-probe spectroscopy. By probing the induced absorption associated with the one-exciton to two-exciton transition, we are able to characterize the time-dependent population densities of states in the upper- and lower-polariton branches following impulsive excitation. We model the time-dependent polariton dynamics and provide direct evidence of a scattering process that returns upper-branch cavity polaritons to states in the exciton reservoir having a rate of (150 fs). A slower process similarly populates lower-branch polaritons by return scattering from the exciton reservoir.