Skyrmions Take Flight!

The exploration of topology in optics and photonics has been a significant area of interest since 1890, focusing on the consideration of singularities in electromagnetic fields. The recent recognition of topology developments in condensed matter physics with the Nobel Prize has sparked a renewed interest in applying condensed matter particle-like topological structures to photonics. Recent advancements, particularly in topological photonics and electromagnetic pulses, offer potential for nontrivial wave-matter interactions, introducing additional degrees of freedom for information and energy transfer.

Despite these developments, the topology of ultrafast transient electromagnetic pulses has remained largely unexplored. In a recent publication in Nature Communications, physicists from the UK and Singapore unveil a novel category of electromagnetic pulses—exact solutions of Maxwell’s equations exhibiting toroidal topology. These pulses, known as supertoroidal topology, allow for continuous control of topological complexity. As these supertoroidal pulses propagate through free space at the speed of light, their electromagnetic fields manifest skyrmionic structures. Skyrmions, originally proposed by Tony Skyrme in 1962, are sophisticated topological particles resembling nanoscale magnetic vortices with captivating textures.

Extensively studied in various condensed matter systems, including chiral magnets and liquid crystals, skyrmions serve as nontrivial excitations crucial for information storage and transfer. The discovery of propagating skyrmions in the form of supertoroidal pulses opens up boundless possibilities for the next generation of informatics revolution. Prof. Nikolay Zheludev, the project supervisor, notes, “This is the first-known example of propagating skyrmions,” highlighting their fundamental topological constructs previously observed in solids as spin formations and localized electromagnetic excitations near metamaterial patterns.

The supertoroidal pulse extends beyond the conventional “Flying Doughnut,” representing a toroidal single-cycle pulse with a space-time non-separable structure linked to vector singularities and non-radiating anapole excitations. With increasingly complex fractal-like toroidal topological structures, the supertoroidal pulse exhibits electromagnetic field configurations with matryoshka-like singular shells, skyrmionic structures of varying skyrmion numbers, and multiple singularities in the Poynting vector field, accompanied by multi-layer energy backflow effects.

The degree of topological complexity is controllable by increasing the supertoroidal order of the pulse. These findings position supertoroidal pulses as a captivating realm for studying topological field configurations and their dynamics. The presented topological features of supertoroidal pulses offer additional degrees of freedom, with potential applications in various fields, including information encoding/decoding schemes involving structured light, optical trapping, manufacturing by light, and particle acceleration. Dr. Yijie Shen, the lead author, emphasizes the novelty of proposing skyrmionic structures in ultrafast structured pulses, suggesting potential applications in high-precision metrology and superresolution imaging.

This work opens avenues for exploring light-matter interaction, ultrafast optics, and topological optics with supertoroidal light pulses and their potential applications in superresolution metrology, imaging, and information and energy transfer.

This article is republished from PhysORG under a Creative Commons license. Read the original article.