Trapped-Mode-Induced Giant Magnetic Field Enhancement in All-Dielectric Metasurfaces

Abstract

Concentrating magnetic field into small volumes raises the intriguing possibility to defy natural convention, where the magnetic component of light generally plays a negligible role in light–matter interactions at optical frequencies. Plasmonic nanostructures have experienced high potential as candidates but are often hindered owing to their high intrinsic losses. Here, with the aid of all-dielectric metasurfaces, it is theoretically demonstrated that the magnetic field can be greatly enhanced based on the trapped mode excitation. The enhancement achieved in the accessible region of the metasurfaces ranges from several hundred to more than 1000-fold by altering geometrical parameters. It is noteworthy that the physical thickness of the metasurfaces is well within the deep subwavelength region, with only ∼1/15 of the resonance wavelength. This work may facilitate designs in enhancing magnetic dipole transitions in natural materials, along with other magnetism-related physical phenomena that demand magnetic hotspot generation.