Observation of magnetic-field-induced optical vortex-antivortex pair

Optical vortices, topological textures in electromagnetic waves, received significant attention in high-dimensional communication and optical manipulations. Unlike the topological textures in other physical systems, optical vortices have been considered passive field distribution, non-interactive to the external stimulus. This work demonstrated magnetic field-induced generation and manipulation of optical vortex-antivortex pair in a gradient-thickness optical cavity (GTOC). GTOC consists of Al/SiO₂/Ni/SiO₂ quad-layer with two-dimensional thickness variation in the top and bottom SiO₂ layers. In the generalized parameter space with thicknesses of SiO2 layers, GTOC reveals a non-trivial topological phase in the specific ranges of Ni layer thicknesses, generating optical vortex-antivortex pair in reflected light. The magneto-optic effect enables the control of an effective thickness change in the Ni layer which is the control parameter of the topological phases. In the experiment, we confirmed the existence of the non-trivial topological phase of GTOC by the bijection of synthetic dimension into real space. We demonstrated magnetically-induced generation and manipulation of the optical vortex-antivortex pair based on the topological phase transition of GTOC.