Observation of bright polariton solitons in a semiconductor microcavity

Microcavity polaritons are composite half-light half-matter quasiparticles, which have recently been demonstrated to exhibit rich physical properties, such as nonequilibrium condensation, parametric scattering and superfluidity. At the same time, polaritons have important advantages over photons for information processing, since their excitonic component leads to weaker diffraction and stronger inter-particle interactions, implying, respectively, tighter localization and lower powers for nonlinear functionality. Here we present the first experimental observations of bright polariton solitons in a strongly coupled semiconductor microcavity. The polariton solitons are shown to be micron-scale localised nondiffracting wavepackets with a corresponding broad spectrum in momentum space. Unlike solitons known in Bose condensed atomic gases, they are nonequilibrium and rely on a balance between losses and external pumping. Microcavity polariton solitons are excited on picosecond timescales, and thus have benefits for the information processing over the light only solitons in semiconductor cavity lasers, which have nanosecond response time.