Mechanisms of blueshifts in organic polariton condensates

Bose-Einstein condensates of exciton-polaritons in inorganic semiconductor microcavities are known to possess strong interparticle interactions attributed to their excitonic component, manifesting as energy blueshifts. However, the localized nature of Frenkel excitons in strongly coupled organic microcavities precludes interparticle Coulomb exchange-interactions, altering the mechanisms of nonlinearity and blueshifts. Here we unravel the origins of blueshifts in organic polariton condensates by examining contributions from the intracavity optical Kerr effect, gain-induced frequency pulling, polariton interactions, and saturation effects of optical transitions for weakly- and strongly-coupled molecules. We conclude that blueshifts arise from the interplay of saturation effects and intermolecular energy migration. Our model predicts the commonly observed step-like increase of both the emission energy and degree of linear polarization at the polariton condensation threshold.

Timur Yagafarov, Denis Sannikov, Anton Zasedatelev, Kyriacos Georgiou, Anton Baranikov, Oleksandr Kyriienko, Ivan Shelykh, Lizhi Gai, Zhen Shen, David Lidzey, Pavlos Lagoudakis