A dielectric metasurface for controllable generation of tightly focused vector beams

Tightly focused vector beams (TFVBs) play an important role in optical microscopy, laser processing and optical micromanipulation due to their unique polarization and intensity distribution. Conventional implementation of TFVBs requires a series of bulky optical elements, increasing the complexity and possibility of optical loss. Here, we present a method for directly generating TFVBs under illumination of linearly polarized lights based on a single dielectric metasurface. The metasurface is designed using geometric phase of anisotropic dielectric meta-atoms with identical shape but varying rotation angles. Under illumination of horizontally and vertically polarized lights, it is demonstrated that TFVBs with pure longitudinal and transverse fields can be generated respectively. In addition, more different TFVBs can be generated by simply altering the polarization of incident light. Furthermore, the metasurface is demonstrated to work well within a broad band ranging from 530 to 730 nm. The proposed strategy provides a minimalist design of a metasurface for controllably generating TFVBs, which offers promising opportunities to generate more complex vector beams for advanced applications in particle trapping and data storage.