Graphene plasmonic skyrmion lattices generated by radially polarized light beams

Topological quasiparticles with sophisticated vectorial structures such as skyrmions play a key role in a variety of physical systems, ranging from quantum fields to magnetic materials. Wherein, optical skyrmions have attracted great attention due to their potential applications in optical information processing, transfer, and storage. In this paper, tunable plasmonic skyrmion lattices are demonstrated on graphene surfaces, where the graphene plasmons are excited using three pairs of dielectric diffractive gratings with radially polarized light beams. We have found that graphene plasmonic skyrmions with identical field distributions at different excited wavelengths can be achieved by tuning the Fermi energies without reoptimizing the grating structures, and the unit cell size of graphene plasmonic skyrmion lattices can also be actively tuned by Fermi energies at fixed excitation frequencies. Moreover, synthesized doughnut right-circularly polarized beams can also excite the plasmonic skyrmions in the axial symmetric structure with half the excitation efficiency compared to radially polarized beams. The proposed devices may find applications in optical information storage and manipulation in a chip.