Modulating the topological state of spin angular momentum of the plasmonic field from the segmented semicircular...

Spin and orbital angular momentum of light provide additional degrees of freedom for constructing and manipulating the topological states of light. However, it istill lacks insight into the relationship between the angular momentum of the excitation light and the topological state of the generated surface wave. Here, we investigate the vector texture of spin angular momentum of the plasmonic field by illuminating a segmented semicircular patchwork groove structure with the vortex light. Plasmonic vortices can be observed by mapping the in-plane Poynting vector in the central region of the coupling structure, accompanying by the distinct field patterns. Merons' textures of spin angular momentum can be excited by the interference of the surface plasmon polariton vortex waves. Adjusting the polarization state and orbital angular momentum of the incident light, the topological state of spin angular momentum of the excited plasmonic field can be actively modulated, and the total skyrmion number (topological winding number) within the central region of the coupling structure can be manipulated between zero, a fraction, and an integer. This result provides, to our knowledge, a new approach to manipulating the topological state of surface waves, facilitating the design and optimization of topological photonic devices.