Dynamic spatiotemporal beams that combine two independent and controllable orbital-angular-momenta using multiple optical-frequency-comb lines

Zhe Zhao,Haoqian Song,Karapet Manukyan,Robert W Boyd,Brittany Lynn,Cong Liu,Moshe Tur,Alan E Willner,Huibin Zhou,Kai Pang,Ahmed Almaiman,Runzhou Zhang,Hao Song

doi:10.1038/s41467-020-17805-1

Abstract

Novel forms of beam generation and propagation based on orbital angular momentum (OAM) have recently gained significant interest. In terms of changes in time, OAM can be manifest at a given distance in different forms, including: (1) a Gaussian-like beam dot that revolves around a central axis, and (2) a Laguerre-Gaussian (LG_{ell ,p}) beam with a helical phasefront rotating around its own beam center. Here we explore the generation of dynamic spatiotemporal beams that combine these two forms of orbital-angular-momenta by coherently adding multiple frequency comb lines. Each line carries a superposition of multiple LG_{ell ,p} modes such that each line is composed of a different ell value and multiple p values. We simulate the generated beams and find that the following can be achieved: (a) mode purity up to 99%, and (b) control of the helical phasefront from 2π-6π and the revolving speed from 0.2–0.6 THz. This approach might be useful for generating spatiotemporal beams with even more sophisticated dynamic properties.

Highlights

Novel forms of beam generation and propagation based on orbital angular momentum (OAM) have recently gained significant interest
There are different types of dynamic optical beams that can exhibit simultaneously two forms of orbital angular momenta. One example of such beam propagation is an LG‘;p beam rotating around its beam center while it revolves around another central axis
We note that both such dynamic rotation and revolution can be described by the transverse OAM11; such transverse OAM can be decomposed into different OAM components, which are related to the rotation around beam’s center[15] and the revolution around another central axis[24,25], respectively

Summary

Introduction

Novel forms of beam generation and propagation based on orbital angular momentum (OAM) have recently gained significant interest. The earth propagating around the sun exhibits both rotation around its own Earth center and revolution around a solar central axis[17] These two manifestations of momentum can occur in space during propagation, but yet the beam’s intensity will appear static at any given point of propagation distance[18,19,20,21,22]. E, i Using multiple frequency comb lines, in which each carries an LG‘;p mode with a different ‘ value and the same p value, to generate a Gaussian-like beam dot exhibiting only revolution around a central axis. F, j Using multiple frequency comb lines, in which each carries a superposition of multiple LG‘;p modes with one different ‘ value and multiple p values, to generate an LG3,0 beam exhibiting both dynamic rotation and revolution Earth center and revolution around the solar central axis. c, g A Gaussian beam on a single frequency exhibits no dynamic rotation/revolution. d, h An LG3,0 beam on a single frequency exbibits only dynamic rotation. e, i Using multiple frequency comb lines, in which each carries an LG‘;p mode with a different ‘ value and the same p value, to generate a Gaussian-like beam dot exhibiting only revolution around a central axis. f, j Using multiple frequency comb lines, in which each carries a superposition of multiple LG‘;p modes with one different ‘ value and multiple p values, to generate an LG3,0 beam exhibiting both dynamic rotation and revolution

Methods

Results

Conclusion