Dark superabsorbers with a needle-like radiation

Subwavelength scatterers with overlapping resonant modes would conventionally be expected to break the single-channel (single mode) limit of scattering or absorption cross sections. In contrast, we theoretically and numerically demonstrate that a properly designed subwavelength cylinder can exhibit a counterintuitive response: the scattering cross section becomes nearly zero, while the absorption cross section approaches the extinction cross section. Moreover, in our paradigm, the associated scattering features a needle-like radiation pattern. The finding is derived from the variation principle, which reveals a generic power distribution of scattering enabled by arbitrary modes, independent of system configuration, material parameters, and operating frequency. Given that the system minimally perturbs the incident field, except in the forward direction, and simultaneously has highly directional needle-like radiation, we term the outcome as dark superabsorbers. We present several designs based on multilayered structures composed of realistic materials. Our results can find potential applications in energy harvesting, low-visibility receivers, directive light-matter interaction, and Fresnel diffractive imaging.