Robust Realization of Polariton Lasing from a Higher Order Mode of Bound States in the Continuum.

Bound states in the continuum (BICs) in microcavity polaritons offer a compelling platform for the interplay of photonic topology and excitonic nonlinear features, yet existing studies are mostly restricted to fundamental resonance modes that restrict access to rich multimode interactions. Here, we demonstrate the realization of a robust higher order mode of BIC in FAPbBr3 perovskite photonic crystals, with a meticulous design of energy detuning for photon and exciton resonance. We show numerically that the higher order mode of BIC exhibits excellent resilience against index asymmetry and fabrication perturbations, robustly sustaining high quality factors. On the basis of this platform, we achieve strong coupling between a second order mode of BIC and perovskite excitons and realize polariton lasing operated at room temperature. The polariton lasing exhibits a coherent far-field polarization vortex carrying a topological charge of -1. This work establishes a promising platform for exploring nonlinear polaritonic phenomena and topological light emission.