Experimental Observation of Topological Transition in Optical Multimeron

Topological textures exemplify matter and energy configuration governed by inherent physical laws. Recently skyrmion-like textures possessing fixed topology have been realized in diverse optical systems, ranging from evanescent fields, structured media to free space. Magnetic skyrmions, with their tunable topological features via external stimuli, hold promise for innovative devices, such as memory, logic gates, and neuromorphic computing. However, achieving dynamic control over non-trivial topological transitions in optical counterparts remains elusive, limiting their application in areas such as super-resolution imaging and information processing. In this study, a platform is proposed and demonstrated for producing optical spin multimerons via multiple plasmonic vortex interference. More importantly, to manipulate the multimeron topology is managed by tuning the topology of the incident light, experimentally observing a topological transition with a nontrivial swap of the skyrmion number. This work broadens the scope of optical topological textures or quasiparticles, providing insights into their formation and transition mechanisms.