Exciton polaritons in semiconductor waveguides

We report the observation of strong coupling between quantum well excitons and a guided mode of a semiconductor planar waveguide by observation of anticrossing in the dispersion. Strong spatial confinement of the optical mode allows a splitting between the two polariton modes of 5–6 meV for a single quantum well. Polaritons on resonance are shown to propagate with a characteristic decay length of 280 μm and a group velocity of 26 μm ps−1. This is a promising first step towards developing an alternative to microcavities for the study of rapidly propagating polaritons, which is particularly well suited to prospective on-chip polaritonic circuit applications.