Optimal backward light scattering by dipolar particles

Abstract

The near-zero forward intensity condition for light scattering by a dielectric dipolar sphere is usually associated with the generalized second Kerker condition, at which equal amplitude electric and magnetic dipolar responses are phase-shifted by π. As we show, this condition does lead to optimal backward light scattering for a given scattering cross section. However, it is clearly insufficient to give rise to the nearly zero optical forward scattering, in striking contrast to the actual view of the problem. In fact, we show that the generalized second Kerker condition leads to an energy radiation pattern that ranges all possible optical scattering diagrams depending on the total scattering cross section. Interestingly, we demonstrate that optimization of backward intensity, near the electric and magnetic dipolar resonances, leads to the counterintuitive result of a far-field energy radiation pattern with nearly zero backscattering.