Long-range propagation of Bloch surface wave polaritons in ZnO

Strongly coupled exciton-polaritons can be observed in a wide variety of systems and exhibit remarkable properties due to their small mass, compared to that of electrons, and their bosonic nature. This allows to study quantum condensates and can be exploited for photonic integrated circuits. For the latter one, the small propagation length of the polaritons in microcavities often comprises a limiting factor. By using evanescent guided modes as the photonic component instead of cavity photons, the polaritons inherit longer lifetimes. In this work, we report on the observation of propagating polaritons, consisting of interacting Bloch surface waves and excitons in ZnO, at room temperature and find energy dependent propagation lengths of up to 100 μm. These results open the path to applying Bloch polaritons in on-chip polaritonic devices requiring macroscopic propagation at or above room temperature.