Enhanced Two‐Photon Excited Emission of Quantum Emitters by Colloidal Plasmonic Metasurfaces

Colloidal plasmonic metasurfaces are emerging as versatile platforms for advancing nanophotonic applications, whose rational design of increasing complexity allows for tailoring and integrating advanced plasmonic and photonic optical properties. Traditional lithographic techniques limit crystallographic and chemical adaptability, hindering the dynamic tuning of optical properties. In this work, a template‐assisted self‐assembly approach for achieving plasmonic metasurfaces using colloidal silver nanoparticle arrays and a thin film of core–shell CdSe/ZnS quantum dots are demonstrated. This system leverages plasmonic surface lattice resonances to create open nanophotonic cavities that enhance the two‐photon excited emission process. The near‐field interactions within these nanophotonic structures offer spectral tunability and efficient light–matter coupling. Moreover, using synthetic nanoparticles enables the integration of a rich library in nanoparticles’ size, shape, and composition, positioning them as promising candidates for compact and scalable photonic devices targeting nonlinear optical processes, advanced sensing, and dynamic light manipulation.