Nondiffracting supertoroidal pulses and optical "Kármán vortex streets"

Nondiffracting supertoroidal pulses and optical "Kármán vortex streets"

07 June 2024 | Yijie Shen, Nikitas Papasimakis & Nikolay I. Zheludev
This article introduces nondiffracting supertoroidal pulses (NDSTPs), a new type of light pulse that maintains its topological properties over long distances. Unlike traditional supertoroidal pulses, which lose their structure during propagation, NDSTPs are designed to remain stable and retain their unique field configurations, including skyrmionic and vortex patterns. The field structure of NDSTPs resembles the von Kármán vortex street, a pattern of swirling vortices observed in fluid and gas dynamics, which can stably propagate forward. NDSTPs are generated using a mathematical framework based on the "electromagnetic directed-energy pulse trains" (EDEPTs) theory, which allows for the creation of focused, finite-energy, space-time non-separable electromagnetic pulses. The pulse is constructed using a scalar generating function that satisfies Helmholtz’s scalar wave equation. The parameters of the pulse, such as the transverse divergence and longitudinal divergence, are carefully controlled to ensure the pulse remains nondiffracting over long distances. The topological properties of NDSTPs include fractal-like singularities, energy backflow, and stable vortex configurations that persist during propagation. These properties make NDSTPs promising for applications in information and energy transfer. Additionally, the magnetic field distribution of NDSTPs exhibits complex topological structures, including vector singularities of vortex and saddle types, and multiple electromagnetic skyrmions that persist during propagation. The optical analogy of Kármán vortex streets (KVS) is also explored, where the vortex arrays in NDSTPs form a striking trail of two-vortex clusters that propagate in a periodic staggered manner, similar to KVS in fluid dynamics. This suggests a potential for using NDSTPs in applications involving fluid transport and energy flow. The study also highlights the potential of NDSTPs for long-distance information transfer and their applications in spectroscopy of toroidal excitations in matter. The robust topological structure of NDSTPs, which remains invariant upon propagation, could be used for telecommunications, remote sensing, and LIDAR. The research provides a new platform for studying the propagation dynamics of electromagnetic skyrmions and their interactions with matter in complex media.This article introduces nondiffracting supertoroidal pulses (NDSTPs), a new type of light pulse that maintains its topological properties over long distances. Unlike traditional supertoroidal pulses, which lose their structure during propagation, NDSTPs are designed to remain stable and retain their unique field configurations, including skyrmionic and vortex patterns. The field structure of NDSTPs resembles the von Kármán vortex street, a pattern of swirling vortices observed in fluid and gas dynamics, which can stably propagate forward. NDSTPs are generated using a mathematical framework based on the "electromagnetic directed-energy pulse trains" (EDEPTs) theory, which allows for the creation of focused, finite-energy, space-time non-separable electromagnetic pulses. The pulse is constructed using a scalar generating function that satisfies Helmholtz’s scalar wave equation. The parameters of the pulse, such as the transverse divergence and longitudinal divergence, are carefully controlled to ensure the pulse remains nondiffracting over long distances. The topological properties of NDSTPs include fractal-like singularities, energy backflow, and stable vortex configurations that persist during propagation. These properties make NDSTPs promising for applications in information and energy transfer. Additionally, the magnetic field distribution of NDSTPs exhibits complex topological structures, including vector singularities of vortex and saddle types, and multiple electromagnetic skyrmions that persist during propagation. The optical analogy of Kármán vortex streets (KVS) is also explored, where the vortex arrays in NDSTPs form a striking trail of two-vortex clusters that propagate in a periodic staggered manner, similar to KVS in fluid dynamics. This suggests a potential for using NDSTPs in applications involving fluid transport and energy flow. The study also highlights the potential of NDSTPs for long-distance information transfer and their applications in spectroscopy of toroidal excitations in matter. The robust topological structure of NDSTPs, which remains invariant upon propagation, could be used for telecommunications, remote sensing, and LIDAR. The research provides a new platform for studying the propagation dynamics of electromagnetic skyrmions and their interactions with matter in complex media.
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