Multiband superbackscattering via mode superposition in a single dielectric particle

The superposition of resonances in a subwavelength particle can be used to achieve powerful scattering beyond the single channel limit and can also determine the directionality of scattered radiation. It has been proposed that by overlapping modes only with equivalent polarity in the far-field, a “superbackscattering” condition, where the total backscattered power is maximized, can be achieved. This effect can be observed through the simple geometry of a high permittivity, subwavelength sphere with a hollow core, and we demonstrate this experimentally by comparing the radar cross section (RCS) of such structures, attaining a doubling of the RCS compared to a solid particle. Furthermore, we show that several sets of modes can be overlapped at once, leading to a multiband, superbackscattering effect.