Whispering Gallery Mode Lasing from Perovskite Polygonal Microcavities via Femtosecond Laser Direct Writing

Organic-inorganic halide perovskites have excellent intrinsic properties, such as long carrier lifetime, high photoluminescence quantum yield, and high gain, in whispering gallery mode (WGM) cavities by facile vapor self-assembly or solution process, which make them competitive for high-performance microlasers. However, the performance of perovskite-based microlasers is severely limited by the fabrication of microcavities, which results in poor reproducibility and uncontrolled morphology. Herein, we explore a reproducible method which combined thermal co-evaporation with femtosecond (fs) laser direct writing for formamidinium lead iodide (FAPbI₃) perovskite polygon-shaped WGM microcavities. The microlasers pumped with the fs laser had a low threshold of 4.0-12.3 μJ/cm² and narrow full width at half-maximum of 0.62-1.05 nm. Moreover, size- and shape-dependent WGM lasing performances are also investigated systematically. The results prove that FAPbI₃ polygonal microcavities can serve as promising WGM lasers and have great potential for practical optoelectronic applications.