Generation of Switchable Singular Beams with Dynamic Metasurfaces.

Ping Yu,Jianxiong Li,Shuang Zhang,Na Liu,Michael Hirscher,Xin Li,Gisela Schütz

doi:10.1021/acsnano.9b02425

Abstract

Singular beams have attracted great attention due to their optical properties and broad applications from light manipulation to optical communications. However, there has been a lack of practical schemes with which to achieve switchable singular beams with sub-wavelength resolution using ultrathin and flat optical devices. In this work, we demonstrate the generation of switchable vector and vortex beams utilizing dynamic metasurfaces at visible frequencies. The dynamic functionality of the metasurface pixels is enabled by the utilization of magnesium nanorods, which possess plasmonic reconfigurability upon hydrogenation and dehydrogenation. We show that switchable vector beams of different polarization states and switchable vortex beams of different topological charges can be implemented through simple hydrogenation and dehydrogenation of the same metasurfaces. Furthermore, we demonstrate a two-cascade metasurface scheme for holographic pattern switching, taking inspiration from orbital angular momentum-shift keying. Our work provides an additional degree of freedom to develop high-security optical elements for anti-counterfeiting applications.

Highlights

Vector and vortex beams are the forms of singular beams based on spatial distributions of polarization and phase, respectively
We demonstrate the generation of switchable vector and vortex beams utilizing dynamic metasurfaces at visible frequencies
We show that switchable vector beams of different polarization states and switchable vortex beams of different topological charges can be implemented through simple hydrogenation and dehydrogenation of the same metasurfaces

Summary

Introduction

Vector and vortex beams are the forms of singular beams based on spatial distributions of polarization and phase, respectively. A metasurface is an artificial nanostructured interface that manipulates light by spatially arranged meta-atoms These meta-atoms, usually consisting of plasmonic or dielectric nanoantennas, can locally control light properties such as phase, amplitude, and polarization.[12,13] Metasurfaces have enabled a family of ultrathin and flat optical elements, which lead to a plethora of optical functionalities including light focusing and steering,[14] holography,[15,16] imaging,[17−19] and vector and vortex beam generation,[20−24] among others. The dynamic functionality of the metasurface pixels is enabled by the utilization of magnesium (Mg) nanorods, which possess plasmonic reconfigurability upon hydrogenation and dehydrogenation.[28,29] Mg can undergo a phase transition from metal to dielectric upon H2 loading, forming magnesium hydride (MgH2). This work features a paradigm for realization of compact and multitasking dynamic optical elements

Methods

Results

Conclusion