Topological robustness of optical skyrmions in underwater turbulent channels

Abstract

Optical skyrmions are polarisation-structured light fields whose Stokes vectors form topologically non-trivial mappings on the Poincaré sphere. We numerically investigate the propagation of Néel-type optical skyrmions over a 20 m underwater turbulent channel modelled by the Nikishov spectrum and a split-step angular-spectrum method. Robustness is quantified using an effective finite-aperture skyrmion number reconstructed from the normalised Stokes field. Under moderate turbulence, about 60% of the initial value is retained after 20 m. Using a common Jones-vector field fidelity under matched conditions, skyrmions outperform LG1 0 orbital-angular-momentum and radially polarised beams by 4.24% and 4.52%, respectively. Parameter studies show that unit-charge skyrmions with larger beam waists and a wavelength of 532 nm are more robust, while Néel and Bloch textures perform similarly. The enhanced resilience arises from common-mode phase perturbations and the globally distributed polarisation topology.