Cost‐Effective Fabrication of Plasmonic Nanoarrays Using Nanosphere‐Lithography for Low‐Threshold Lasers and High‐Bandwidth Optical Communication

Abstract Plasmonic lasers emerge as promising candidates for next‐generation photonic devices because they confine light at subwavelength scales and enable ultra‐compact optical systems. However, these devices face challenges like complex fabrication, high costs, high laser thresholds, and difficulties in large‐area uniformity and optimal light‐matter coupling. In this study, low‐cost nanosphere lithography is used to fabricate large‐area curved silver triangular arrays, which are coupled with CsPbBr 3 quantum dots to realize a low‐threshold laser. By controlling the injection rate with a syringe pump, a large‐area, uniform polystyrene colloid sphere monolayer and silver triangular arrays are prepared. Finite‐difference time‐domain simulations and time‐resolved photoluminescence measurements systematically investigate the effects of microsphere size and Ag nanoparticle thickness on plasmonic resonance, photoluminescence enhancement, and emission dynamics. Optimizing Ag thickness (50–150 nm) aligns nanoarray resonance with exciton transition, enabling strong coupling and a 12.6 Purcell factor. The optimized devices exhibit a low lasing threshold of 6.3 µJ∙cm −2 , an ultrahigh Q‐factor of 888 ± 20, and a lifetime of 5 ps. Additionally, a THz optical encoder with a maximum modulation bandwidth of 0.03 THz demonstrates potential for optical communication. This work underscores the importance of precise nanostructure fabrication in optimizing plasmonic laser performance.