Geometric Metasurface Fork Gratings for Vortex Beam Generation and Manipulation

TL;DR

This paper introduces a novel geometric metasurface fork grating that efficiently generates and manipulates optical vortex beams with orbital angular momentum, enabling advanced control over light's spin and orbital properties.

Contribution

It presents a new metasurface design that combines vortex beam generation and wave propagation control in a single, planar device, simplifying fabrication and enhancing functionality.

Findings

Successfully demonstrated vortex beam generation with arbitrary OAM

Achieved simultaneous control of spin and orbital angular momentum

Enabled planar, integrated manipulation of light properties

Abstract

In recent years, optical vortex beams possessing orbital angular momentum have caught much attention due to their potential for high capacity optical communications. This capability arises from the unbounded topological charges of orbital angular momentum (OAM) that provides infinite freedoms for encoding information. The two most common approaches for generating vortex beams are through fork diffraction gratings and spiral phase plates. While realization of conventional spiral phase plate requires complicated 3D fabrication, the emerging field of metasurfaces has provided a planar and facile solution for generating vortex beams of arbitrary orbit angular momentum. Here we realize a novel type of geometric metasurface fork grating that seamlessly combine the functionality of a metasurface phase plate for vortex beam generation, and that of a linear phase gradient metasurface for controlling the wave propagation direction. The metasurface fork grating is therefore capable of simultaneously controlling both the spin and the orbital angular momentum of light.