: Myungjae Lee, Ségolène Callard, Christian Seassal and Heonsu Jeon

: Nature Photonics 13(7), 445-448 (2019)

DOI https://doi.org/10.1038/s41566-019-0407-5 Random lasers are fascinating devices due to the absence of a conventional cavity structure and their counterintuitive lasing mechanism. However, they are also notorious for their unpredictability. Despite their many unusual properties, random lasers are unlikely to achieve the ubiquitous acceptance of conventional lasers unless the underlying lasing mechanisms that govern their operation are thoroughly understood and their exotic properties are appropriately regulated. Recent demonstrations of localized random lasers are considered a breakthrough in the field because structural disorders were engineered in a top-down manner. Nevertheless, the origin of the lasing phenomenon and the controllability of these devices have not been adequately addressed. Lately, we have experimentally proven that photonic band-tail eigenstates— manifestations of photonic Anderson localizations—are responsible for random lasing in a compositionally disordered photonic crystal platform. Herein, we demonstrate that the process of governing the band-tail states offers a unique opportunity to finally regulate random lasers. *Selected for the cover image of the July 2019 issue