Tying Polarization-Switchable Optical Vortex Knots and Links via Holographic All-Dielectric Metasurfaces

Tailoring the spatial structure of light field in multiple degrees of freedom is a research hotspot in recent years. The topology of light field, as one of the most fascinating structures, such as vortex knots and links associated with the phase singularities, is evoking increasing attention both in fundamental research and practical application. Here, an all-dielectric metasurface device is proposed and experimentally demonstrated that can construct vortex knots and links in light field at the micro scale. These two distinct topological configurations can be switched by changing the incident polarization. Utilizing the digital holographic interference method, these topological configurations of vorticity lines are accurately characterized in three-dimensions, and the topology-preserving evolution of such ultra-small fields is demonstrated. These two classical configurations exemplify the capability of multichannel manipulating topology by compact metadevice. The work may promote the application of structured light filed at the micro scale and even the creation of other physical fields with ultra-small size.