Enabling Low‐Threshold Random Lasing by Transforming Intrinsic Disorder Into Efficient Feedback in Quasi‐2D Tin‐Based Perovskites

ABSTRACT Engineering optical feedback is critical for achieving low‐threshold lasing in gain media with high intrinsic losses. However, achieving this through a controllable and reproducible engineering of the scattering landscape, rather than relying on intrinsic disorder, remains a significant challenge for random lasers. Here, a powerful strategy to control random lasing in quasi‐2D tin‐based perovskites is demonstrated by structuring the film's surface via thermal imprinting. This strategy makes the random feedback “less random” and more efficient, though its effectiveness exhibits a complex, non‐monotonic dependence on the film's thickness. A comprehensive model is then established to deconvolve the competing effects of optical confinement, scattering, and waveguiding that govern this behavior. Guided by this model, imprinting an optimized grating is shown to not only lower the random lasing threshold but also enhance the operational stability under prolonged excitation. The general applicability of this approach is verified in a different tin‐based perovskite composition, and its potential is highlighted by the demonstration of a low‐threshold, speckle‐free NIR light source. This work establishes “scattering engineering” as a practical design tool to transform intrinsically limited materials into high‐performance, functionalized photonic devices.