Achieving Tunable Amplified Spontaneous Emission in Rb-Cs Alloyed Quasi-2D Perovskites with Low Threshold and...

Blue-green lasers are essential for next-generation optoelectronics. While GaN-InGaN lasers offer excellent performance, their complex fabrication and challenges in precise bandgap tuning remain significant limitations. Hybrid lead halide perovskites present a promising alternative, with tunable bandgaps and cost-effective solution processing. However, halide migration in these materials causes spectral instability and luminescence shifts under operational conditions. Here, a novel class of Rb-Cs alloyed quasi-2D perovskites is introduced that achieve both low amplified spontaneous emission (ASE) thresholds and exceptional spectral stability. By precisely tuning the Rb-Cs ratio, it realizes ASE across the blue-green spectrum (481-532 nm). Rb-Cs alloying critically modulates the quantum well distribution, optimizes the energy landscape, and suppresses Auger recombination, resulting in a record-low ASE threshold of 1.94 µJ·cm^-2-over 50% lower than that of mixed-halide perovskites. These materials exhibit remarkable spectral robustness, with ASE spectra remaining stable even after prolonged thermal annealing, thereby overcoming halide migration-induced degradation. Furthermore, micro-ring laser arrays fabricated from these Rb-Cs alloyed perovskites demonstrate superior lasing characteristics, including high-quality whispering-gallery-mode resonances and low lasing thresholds, underscoring their potential for advanced laser technologies.