Nondiffracting supertoroidal pulses and optical “Kármán vortex streets”

Supertoroidal light pulses, as space-time nonseparable electromagnetic waves, exhibit unique topological properties including skyrmionic configurations, fractal-like singularities, and energy backflow in free space, which however do not survive upon propagation. Here, we introduce the non-diffracting supertoroidal pulses (NDSTPs) with propagation-robust skyrmionic and vortex field configurations that persists over arbitrary propagation distances. Intriguingly, the field structure of NDSTPs has a similarity with the von Kármán vortex street, a pattern of swirling vortices in fluid and gas dynamics with staggered singularities that can stably propagate forward. NDSTPs will be of interest as directed channels for information and energy transfer applications. Topological waves and their exotic properties are attracting intense research interest. Here, the authors report on the discovery of supertoroidal electromagnetic pulses with robust skyrmionic topology that persists upon propagation over arbitrarily long distances.