Impact of the geometry of the excitation structure on optical skyrmion.

Optical skyrmions have attracted great attention for the potential applications in novel information storage and communication. It is of great significance to get insight into the generation of optical skyrmions by surface waves. Here, we have paid greater emphasis on the influence of the geometry of the coupling structure on the formation of optical skyrmions. Optical skyrmions are constructed from the superposition of the interfering surface plasmons excited by polygon trenches on Ag film. The results show the field texture of optical skyrmions is mainly determined by the excitation structure, with distinct properties revealed with various closed and non-closed geometries. Moreover, the ratio between the electric field strengths of the optical skyrmions can be larger than 4 between the optimized and unoptimized coupling structures. The pattern of the optical skyrmion shows a strong dependence on the excitation structure, implying the significant role in skyrmion topology it plays.