Multichannel polarization-independent vortex beams generation via all-dielectric metasurface

Generating structured light beams has become a research hotspot to target many emerging practical applications like optical sensing, super-resolution imaging, and optical communication. Ingenious tailoring of spatial structures of light helps to manifest several intriguing beams like Bessel beams, Airy beams, vortex beams, etc. Among them, optical vortices (OVs) hold distinctive promise to meet the anticipated demands for optical communication, optical trapping, microscopy, quantum information processing, and many more. Due to their spatial dimensions, traditional methods of generating OVs are not viable to fit with the cutting-edge on-chip optical systems. In contrast, subwavelength structured devices enormously aggravate the capability to realize chip-integrated devices via abrupt phase discontinuity. Besides the many exotic features of optical metasurfaces, their fixed functionality limits the realization of breakthroughs in many real-life applications. Here, we present an exquisite design that enables multifunctional metastructures to develop multichannel focused optical vortices of like or distinct topological charges on the same focal plane regardless of the input polarization state. Our design is based on a symmetric array of nanocylinders where the index waveguide theory concept is utilized effectively to accumulate the desired phase in the direction of propagation. Moreover, zinc sulfide, as a prime material used in device prototyping, enables a highly transmissive structure. Our work regarding the multidimensional generation of optical vortices has far-reaching effects on multifunctional optical devices.