Supercavity lasing

Light in a laser is confined in the form of standing waves. By engineering such waves, scientists have designed an optical system that enhances this confinement, producing a compact laser that emits a high-quality beam. See Letter p.196 Light can be trapped by confining it between mirrors or in a cavity. However, a curious effect of trapping waves in an open system, a continuum, known for almost a century from quantum-mechanics theory, was recently rediscovered as a general phenomenon and applied to acoustics as well as optics. Until now, 'bound in continuum' light states have been realized in passive systems. But here, Boubacar Kanté and colleagues report the construction of nanophotonic structures in which such bound states in a continuum are used to produce laser action at room temperature. The effect could help researchers to explore novel light–matter interaction effects.