External‐Cavity Free Plasmonic Nano‐Lasers Based on Quasi‐2D Perovskite Films

Plasmonic nano‐lasers possess enormous potential for miniaturization of on‐chip integrated light sources. However, achieving plasmonic lasing requires high‐quality plasmonic resonant cavities, which are currently limited by complex, small‐scale, and costly production methods. Here, a new type of external‐cavity free plasmonic nano‐lasers is first presented with ultra‐thin thickness, achieved through the facile spin‐coating of quasi‐2D perovskite films onto monocrystalline silver sheets. The external‐cavity free plasmonic nano‐lasers exhibit obvious lasing behaviors, evidenced by a well‐defined threshold, significant linewidth narrowing, and distinct polarization dependence. The internal lasing mechanism relies on the scattering loop of surface plasmon polaritons (SPPs) by the disordered grains of the polycrystalline perovskite film. Based on this loop, SPPs experience feedback and amplification at the interface between silver sheets and perovskite films, leading to the lasing. Compared to photonic mode lasers, plasmonic nano‐lasers exhibit a significantly reduced feature size (< 80 nm), a dramatically faster lasing dynamic process (17 ps), and enhanced feedback stability and efficiency. The external‐cavity free plasmonic nano‐lasers eliminate the strict requirements for plasmonic resonant cavities to overcome traditional optical diffraction limits, making them highly significant for future applications in on‐chip photoelectric or all‐optical integration.