A New Generation of Liquid Lasers from Engineered Semiconductor Nanocrystals with Giant Optical Gain

With the development of optofluidic technology, liquid lasers have attracted intense interest but still face a formidable challenge due to the lack of qualified gain media and creative device design. Compared to the organic fluorescent dyes and traditional CdSe-based nanocrystals (NCs), the lead-halide perovskite (LHP) NCs feature larger gain coefficient and higher robustness, which renders LHP NCs a promising unexploited liquid gain medium. Herein, for the first time, the hidden principle governing the solution-based light amplification in LHP semiconductor NCs is demystified and it is demonstrated that the LHP NCs are superior solution-phase gain media showing a giant (≈2600 cm−1) optical gain. On this basis, a novel microfluidic laser device is designed and realized that exhibits a record-low pump threshold (≈22.7 µJ cm−2), high Q-factor (≈7480), large output polarization (≈0.91), and long-time robustness over high-intensity operation, which is readily applicable to practical applications. The findings represent a significant step toward the technologically important liquid lasers of the new generation and can advance optofluidic applications. © 2023 Wiley-VCH GmbH.