  Topological photonics provides an important platform for the development of
photonic devices with robust disorder-immune light transport and controllable
helicity. Mixing photons with excitons (or polaritons) gives rise to nontrivial
polaritonic bands with chiral modes, allowing the manipulation of helical
lasers in strongly coupled light-matter systems. In this work, we demonstrate
helical polariton lasing from topological valleys of an organic anisotropic
microcrystalline cavity based on tailored local nontrivial band geometry. This
polariton laser emits light of different helicity along different angular
directions. The significantly enhanced chiral characteristics are achieved by
the nonlinear relaxation process. Helical topological polariton lasers may
provide a perfect platform for the exploration of novel topological phenomena
that involve light-matter interaction and the development of polariton-based
spintronic devices.
