High-speed flow of interacting organic polaritons

The strong coupling of an excitonic transition with an electromagnetic mode results in composite quasi-particles called exciton polaritons, which have been shown to combine the best properties of their individual components in semiconductor microcavities. However, the physics and applications of polariton flows in organic materials and at room temperature are still unexplored because of the poor photon confinement in such structures. Here, we demonstrate that polaritons formed by the hybridization of organic excitons with a Bloch surface wave are able to propagate for hundreds of microns showing remarkable third-order nonlinear interactions upon high injection density. These findings pave the way for the study of organic nonlinear light–matter fluxes and for a technologically promising route of the realization of dissipation-less on-chip polariton devices operating at room temperature. The propagation and energy renormalization of exciton-polaritons, hybrid states of exciton and photon, can be controlled in an organic semiconductor at room temperature. Giovanni Lerario of CNR NANOTEC in Italy and co-workers fabricated a distributed feedback reflector from alternating layers of titanium dioxide and silicon dioxide on a glass substrate and coated it with a 35 nm thick layer of a perylene derivative. This cavity structure supports a novel type of polariton called Bloch surface wave polariton (BSWP), which propagates for more than 100 mm with a group velocity as high as of 150 mm ps-1. The resonance wavelength of the polariton is blue-shifted with increasing pump power into the distributed feedback reflector, indicating that the energy of the BSWP can be tuned. The results give hope for realizing on-chip polariton devices working at room temperature.