Koshelev, KirillKruk, SergeyMelik-Gaykazyan, ElizavetaChoi, Jae-HyuckBogdanov, AndreyPark, Hong-GyuKivshar, Yuri2023-10-042023-10-041-6 Februa0277-786Xhttp://hdl.handle.net/1885/301240Recent developments in the physics of Mie-resonant high-index dielectric nanostructures suggested a promising pathway to improve efficiencies of the nonlinear light conversion beyond the limits imposed by plasmonics. Here, we employ the concept of bound states in the continuum to experimentally demonstrate a sharp enhancement of the second-harmonic generation efficiency at localized states formed via destructive interference of two leaky modes. For an AlGaAs subwavelength disk with optimized parameters, pumped with a structured light and placed on an engineered multilayered substrate, we observe the record-high conversion efficiency compared to the previous demonstrations with isolated subwavelength resonators.The authors acknowledge a financial support from the Australian Research Council (ARC), the Russian Foundation for Basic Research (18-32-20205), and the National Research Foundation of Korea (NRF) under grant no. 2018R1A3A3000666 funded by the Korean Government (MSIT). K.K. and A.B. acknowledge support from the Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS“.application/pdfen-AU© 2020 SPIE202010.1117/12.25442312022-08-07