Subwavelength dielectric resonators for nonlinear nanophotonics

Subwavelength optical resonators made of high-index dielectric materials provide efficient ways to manipulate light at the nanoscale through mode interferences and enhancement of both electric and magnetic fields. Such Mie-resonant dielectric structures have low absorption, and their functionalities are limited predominantly by radiative losses. We implement a new physical mechanism for suppressing radiative losses of individual nanoscale resonators to engineer special modes with high quality factors: optical bound states in the continuum (BICs). We demonstrate that an individual subwavelength dielectric resonator hosting a BIC mode can boost nonlinear effects increasing second-harmonic generation efficiency. Our work suggests a route to use subwavelength high-index dielectric resonators for a strong enhancement of light–matter interactions with applications to nonlinear optics, nanoscale lasers, quantum photonics, and sensors.This work was supported by the Australian Research Council, the Strategic Fund of the Australian National University, the National Research Foundation of Korea (NRF) under grant no. 2018R1A3A3000666 funded by the Korean Government (MSIT), and the Russian Science Foundation under grant no. 18-72-10140. K.K. and A.B. acknowledge support from the Foundation for the Advancement of Theoretical Physics and Mathematics “BASIS.