Abstract: Development of on-chip coherent light sources with desired single-mode operation and straightforward spectral tunability has attracted intense interest due to ever-increasing demand for photonic devices and optoelectronic integration, but still faces serious challenges. Herein, we propose a facile method to synthesize cesium lead halide (CsPbX₃) microstructures with well-defined morphologies, sizes, and constituent element gradient. The scheme is conducted using a chemical vapor deposition (CVD), which is subsequently associated with annealing-assisted solid-solid anion exchange. For the plate-shaped structures, the controllability on the cross-sectional dimension enables to precisely modulate the lasing modes, thus achieving single-mode operation; while tuning the stoichiometric of the halogen anion components in the plate-shaped CsPbI_xBr_3-x alloy samples, the lasing wavelengths are straightforwardly varied to span the entire visible spectrum. By comparison, the experimental scheme on synthesizing alloyed CsPbI_xBr_3-x perovskites is conducted using an in-situ approach, thereby achieving precise modulation of bandgap-controlled microlasers by controlling the reaction time. Such laser properties like controllable microcavity modes and broad stoichiometry-dependent tunability of light-emitting/lasing colors, associated with the facile synthesizing method of monocrystalline CsPbI_xBr_3-x structures, make lead halide perovskites ideal materials for the development of wavelength-controlled microlasers toward practical photonic integration.

Key words: Microlaser, Tunable lasing mode, Annealing-assisted solid-solid anion exchange, In-situ approach, Wavelength-tunable laser, Photostability