Stress Accumulation Induced by Ion Exchange for Synchronous Modulation of Mode and Wavelength in Microlasers

ABSTRACT Achieving simultaneous and precise control over both the emission wavelength and lasing modes in laser architectures holds profound scientific significance for advancing integrated photonics. To date, no physical mechanism has been identified that enables the simultaneous modulation of lasing wavelength and output mode in perovskite microstructures through ion exchange. Here, we report a facile heating‐assisted vapor/solid anion exchange strategy to realize broadly tunable single‐mode microlasers based on pure‐phase single‐crystalline CsPbCl x Br 3‐x microwires. This approach seamlessly integrates bandgap engineering with intrinsic cavity design, where precise control over the halide composition enables continuous, linear wavelength tuning across a broad spectral range of 427–548 nm, the widest tuning range reported to date for Br/Cl anion‐exchange systems. Concurrently, lattice strain induced by ionic radius mismatch facilitates the formation of smooth slits within the microwires, which spatially partition the wirelike structure into mutually coupled Fabry‐Pérot (F‐P) subcavities, thereby enabling robust single‐mode polarized lasing via Vernier effect. Critically, this self‐contained approach maintains high crystalline quality, low threshold, and high quality (Q) factor, entirely circumventing the optical losses associated with external cavities or complex micro/nanofabrication. Combined with theoretical simulations that elucidate the mode selection and far‐field radiation mechanisms, this work establishes a transformative pathway toward multifunctional integrated photonics.