Orbital Angular Momentum Generation Using a Bi-Functional Pancharatnam-Berry Metasurface

Abstract

Recent several works show that metasurfaces possess unprecedented abilities to manipulate the wave front, leading to plenty of fascinating physical phenomena such as anomalous refraction and reflection, focusing lens, holograms, vortex beam generators and so on. Despite of the great stride in this area, it can be noted that most of the meta-devices only concentrate on the modulation of reflection or transmission waves, while leaving the half of electromagnetic waves unexplored. To promote the performance and implement more advanced functionalities, it is meaningful to design metasurfaces which can manipulate the transmitted and reflected electromagnetic waves simultaneously. Here a novel approach is proposed to generate Orbital angular momentum (OAM) via a bi-functional Pancharatnam-Berry metasurface. The metasurface can operate in both transmission and reflection modes, to efficiently manipulate the electromagnetic waves in the full space. The phase of cross-polarized transmitted and co-polarized reflected waves can be simultaneously adjusted by simply rotating the patterns. It can be demonstrated theoretically that, by elaborately arranging the elements with specific phase distributions, the OAM vortex beam can be realized for both transmission and reflection mode. Compared with traditional methods, the metasurface is especially advantageous for low profile, small mass, low manufacturing cost, and design simplicity. Our work extends the approaches of OAM generation and provides a new platform for next generation communication and radar systems.