Inverse design of Mie resonators with minimal backscattering.

Manipulation and engineering of light scattering by resonant nanostructures is one of the central problems in optics and photonics. In this work, we theoretically study the effect of suppressed backscattering of a dielectric nanoantenna. We employed the covariance matrix adaptation evolution strategy (CMA-ES) to identify the geometries of axisymmetric dielectric structures with minimized backward scattering cross section. Zero backscattering is achieved due to the generalized Kerker effect and multipole cancellation condition. We found a set of geometries and shapes of the nanoantenna having backscattering intensity close to zero. With the help of a clustering algorithm, all the found geometries fall separated into several groups according to their multipolar content. While the optical properties of scatterers in each group were similar due to the similar multipolar content, their shapes can be significantly different. This highlights the inherent ambiguity in free-form optimization problems. We believe that the obtained results can help in designing nanophotonic structures such as antireflective metasurfaces and other electromagnetic-based devices.