Broadband Multichannel Cylindrical Vector Beam Generation by a Single Metasurface

Beams with spatially-varying polarization states have been the topic of much interest recently due to the unusual ways in which they can interact with matter. Cylindrical vector beams (CVBs) represent the most commonly used type and feature cylindrically-symmetric polarization distributions. The optical systems employed thus far for their generation have usually only been able to produce a single CVB. To generate and observe multiple CVBs, bulky optical systems with stringent alignment tolerances have been needed. Here, a method to generate an array of CVBs using a single optical element, namely a transmission-mode dielectric metasurface, is demonstrated. The incident light is split into an array of left and right-handed circularly polarized vortex beams that superpose with a controllable phase difference. An array of CVBs with 12 channels over a broad wavelength range is experimentally demonstrated. This study's method produces a significant increase in the number of polarization channels compared to previous reports and solves the long-standing challenge of unequal intensity distributions. It furthermore improves the flexibility of the vector field control by not only generating CVBs of different orders but also controlling their polarization rotation. This method may pave the way for applications in optical communications, laser machining, and optical trapping.