Tunable spatio-spectral Target Skyrmions and topological multiplexing

TL;DR

This paper introduces a method to generate and control spatio-spectral Skyrmions using three degrees of freedom, enabling topological multiplexing for high-capacity optical information transfer.

Contribution

It demonstrates a novel approach to creating tunable, multi-DoF Skyrmions and a new multiplexing strategy for encoding multiple topological states in a single light field.

Findings

Successfully generated spatio-spectral Skyrmions with three controllable DoFs.

Implemented topological multiplexing to encode multiple Skyrmion numbers.

Experimentally transmitted three distinct Skyrmion states in a single optical field.

Abstract

Optical Skyrmions have recently garnered much interest providing a potential avenue for high capacity, robust topological information transfer. Typically, Skyrmions are derived from the coupling of just two degrees of freedom (DoFs) limiting their versatility. In this work we realize spatio-spectral Skyrmions derived from the non-separability between three DoFs: wavelength, space and polarization. A compact and simple technique is used to generate the spatio-spectral vector beams (SSVB) carrying the desired Skyrmionic structure, offering simple pathways for complex Skyrmionic beam design. The topological structure, witnessed through a map between the spatio-spectral plane and the Poincar\'e sphere, exhibits an additional tunable $k\pi$ parameter thereby enhancing the number of controllable DoFs. Our three DoF construction allows us to propose a novel topological multiplexing strategy that independently encodes different Skyrmion numbers at different radii of the field. We experimentally demonstrate the practicality of this approach by transmitting and receiving three distinct Skyrmion numbers encoded into a single topological field, for the first form of mode division multiplexing with Skyrmion topology. This work opens up new avenues for dense information encoding using multiple topological channels encoded in a single light field.