Multipolar engineering of subwavelength dielectric particles for scattering enhancement
Electromagnetic scattering on subwavelength structures keeps attracting attention owing to abroad range of possible applications, where this phenomenon is in use. Fundamental limits of scattering cross-section, being well understood in spherical geometries, are overlooked in cases of low-symmetry resonators. Here, we revise the notion of superscattering and link this property with symmetry groups of the scattering potential. We demonstrate pathways to spectrally overlap several eigenmodes of a resonator in a way they interfere constructively and enhance the scattering cross-section. As a particular example, we demonstrate spectral overlapping of several electric and magnetic modes in a subwavelength entirely homogeneous ceramic resonator. The optimized structures show the excess of a dipolar scattering cross-section limit for a sphere up to a factor of four. The revealed rules, which link symmetry groups with fundamental scattering limits, allow performing and assessing designs of subwavelength supperscatterers, which can find a use in label-free imaging, compact antennas, long-range radio frequency identification, and many other fields.