Optical Anapoles: Concepts and Applications

Interference of electromagnetic modes supported by subwavelength photonic structures is one of the key concepts that underpins the nanoscale control of light in metaoptics. It drives the whole realm of all-dielectric Mie-resonant nanophotonics with many applications for low-loss nanoscale optical antennas, metasurfaces, and metadevices. Specifically, interference of the electric and toroidal dipole moments results in a very peculiar, low-radiating optical state associated with the concept of optical anapole. Here, the physics of multimode interferences and multipolar interplay in nanostructures is uncovered with an intriguing example of the optical anapole. The recently emerged field of anapole electrodynamics is reviewed, explicating its relevance to multipolar nanophotonics, including direct experimental observations, manifestations in nonlinear optics, and rapidly expanding applications in nanoantennas, active photonics, and metamaterials.