# Nonradiating Photonics with Resonant Dielectric Nanostructures

## TL;DR

This paper reviews recent advances in nonradiating photonic states in dielectric nanostructures, highlighting their physics, differences, and potential applications in enhancing light-matter interactions at the nanoscale.

## Contribution

It provides a comprehensive overview of nonradiating states like anapoles and bound states in the continuum in dielectric metasurfaces, emphasizing their physics and applications.

## Key findings

- Recent experimental demonstrations of nonradiating states
- Applications in nonlinear optics and high-Q resonances
- Potential for nanoscale light control and enhancement

## Abstract

Nonradiating sources of energy have traditionally been studied in quantum mechanics and astrophysics, while receiving a very little attention in the photonics community. This situation has changed recently due to a number of pioneering theoretical studies and remarkable experimental demonstrations of the exotic states of light in dielectric resonant photonic structures and metasurfaces, with the possibility to localize efficiently the electromagnetic fields of high intensities within small volumes of matter. These recent advances underpin novel concepts in nanophotonics, and provide a promising pathway to overcome the problem of losses usually associated with metals and plasmonic materials for the efficient control of the light-matter interaction at the nanoscale. This review paper provides the general background and several snapshots of the recent results in this young yet prominent research field, focusing on two types of nonradiating states of light that both have been recently at the center of many studies in all-dielectric resonant meta-optics and metasurfaces: optical {\em anapoles} and photonic {\em bound states in the continuum}. We discuss a brief history of these states in optics, their underlying physics and manifestations, and also emphasize their differences and similarities. We also review some applications of such novel photonic states in both linear and nonlinear optics for the nanoscale field enhancement, a design of novel dielectric structures with high-$Q$ resonances, nonlinear wave mixing and enhanced harmonic generation, as well as advanced concepts for lasing and optical neural networks.