Solution‐Processed Perovskite Quantum Dot Quasi‐BIC Laser from Miniaturized Low‐Lateral‐Loss Cavity

Abstract Laser devices produced via solution‐processed perovskite quantum dots (QDs) offer broad spectral tunability as well as ease of fabrication. Utilizing quasi‐bound states in the continuum (quasi‐BIC) modes, solution‐processed QD laser devices have been demonstrated with a nanostructure coated in a thin‐film gain media configuration. However, light leakage through thin‐film guiding from the cavity side edges becomes more pronounced when shrinking the cavity size, posing challenges for the miniaturization of quasi‐BIC‐based lasers. Here, the fabrication of well‐defined patterns of QDs via a solution process allows them to take advantage of the pattern edges to reduce losses through the cavity edges. A single‐mode BIC laser is reported by using CsPbBr₃ QDs with a narrow linewidth of ≈0.1 nm. Importantly, a miniaturized quasi‐BIC laser is realized with a device size as small as 10 × 10 µm², making it the smallest among existing solution‐processed BIC lasers. This work provides a strategy for developing ultra‐compact BIC lasers via solution‐processed gain media.