Particlelike topologies in light
Abstract
Threedimensional (3D) topological states resemble truly localised, particlelike objects in physical space. Among the richest such structures are 3D skyrmions and hopfions, that realise integer topological numbers in their configuration via homotopic mappings from real space to the hypersphere (sphere in 4D space) or the 2D sphere. They have received tremendous attention as exotic textures in particle physics, cosmology, superfluids, and many other systems. Here we experimentally create and measure a topological 3D skyrmionic hopfion in fully structured light. By simultaneously tailoring the polarisation and phase profile, our beam establishes the skyrmionic mapping by realising every possible optical state in the propagation volume. The resulting light field's Stokes parameters and phase are synthesised into a Hopf fibration texture. We perform volumetric fullfield reconstruction of the Π_{3}? mapping, measuring a quantised topological charge, or Skyrme number, of 0.945. Such topological state control opens avenues for 3D optical data encoding and metrology. The Hopf characterisation of the optical hypersphere endows a fresh perspective to topological optics, offering experimentallyaccessible photonic analogues to the gamut of particlelike 3D topological textures, from condensed matter to highenergy physics.
 Publication:

Nature Communications
 Pub Date:
 November 2021
 DOI:
 10.1038/s41467021261715
 arXiv:
 arXiv:2107.10810
 Bibcode:
 2021NatCo..12.6785S
 Keywords:

 Physics  Optics;
 Condensed Matter  Mesoscale and Nanoscale Physics;
 High Energy Physics  Theory
 EPrint:
 Main text: 9 pages, 4 figures