Generation of superhelical time-varying OAM beam with space-time-coding digital metasurface

TL;DR

This paper presents a novel microwave metasurface design that generates superhelical, time-varying orbital angular momentum beams with dynamic wavefront control, enabling advanced particle manipulation and communication applications.

Contribution

It introduces a space-time-coding digital metasurface for scalable generation of time-varying OAM and the concept of superhelicity with higher-order wavefront twists.

Findings

Successfully generated superhelical time-varying OAM beams in microwave frequencies.

Developed a two-probe measurement technique for dynamic OAM field mapping.

Demonstrated potential applications in particle manipulation and OAM multiplexing.

Abstract

The recently proposed extreme-ultraviolet (EUV) beams with time-varying orbital angular momentum (OAM) realized by high-harmonic generation (HHG) provides extraordinary tools for quantum excitation control and particle manipulation. However, such an approach is not easily scalable to other frequency regimes. Here, we design a space-time-coding digital metasurface operating in microwave frequencies to experimentally generate different modes of time-varying OAM. We also introduce a concept of superhelicity of time-varying OAM with a higher-order twist of the wavefront structure, which can be further realized by reflection phase profiles nonlinear in time through the metasurface. By developing a two-probe measurement technique, we dynamically map the OAM field pattern varying in time. The proposed superhelical time-varying OAM beam paves a way for particle manipulations and OAM multiplexing communications.