Moiré metasurface for dynamically tuned vector beams.

Abstract

The vector beam (VB), characterized by the spatially non-uniform distribution of polarization states, shows broad prospects in the photonics field. Recently, the development of metasurfaces offers novel (to the best of our knowledge) opportunities for manipulating VB, yet most efforts lack dynamic control over its polarization order. In this Letter, a general and facile method for dynamically tuning the polarization order of VB is proposed and validated by a silicon-based Moiré metasurface in the visible band. The continuous phase tunability of the Moiré effect is first utilized to tailor the topological charges of a focused vortex beam. Furthermore, geometric phase is specially induced in designing the Moiré metasurface so that two vortex beams carrying opposite topological charges can be accomplished upon orthogonal circular-polarization incidences. Consequently, under linear polarization incidence, the superposition of the vortex beams finally leads to the generation of a VB, whose polarization order is dynamically tuned by rotating the Moiré metasurface. We anticipate that the proposed method will provide promising prospects in meta-optics with reconfigurable functionalities.