Enhanced energy localization in electromagnetically thick metallic mesoshells

Abstract

While subwavelength dielectric structures enclosed by a thin metallic nanoshell have found a wide range of applications, their wavelength-scale counterparts have not been addressed. Conventionally, a dielectric enclosed by a thick metallic shell is considered isolated as the fields attenuate to a negligible value. Here, we show that, due to the Mie resonances of the wavelength-scale dielectric core, the energy density in the core can be enhanced by six orders of magnitude as compared to the off-resonance case, despite the presence of a thick metallic shell. In contrast to the widely studied case of plasmonic core-shell subwavelength particles, where the field enhancement occurs at the boundary of the metallic shell, the thick metallic shell surrounding the wavelength-scale dielectric core provides a strong energy confinement at the center of the core at longer wavelengths, where plasmonic effects are negligible. The observed enhancement can find applications for the probing of shielded materials and designing structures with engineered electromagnetic responses.