Focal beam structuring by triple mixing of optical vortex lattices

Lyubomir Stoyanov,Ivan Stefanov,Gerhard G Paulus,Georgi Maleshkov,Alexander Dreischuh

doi:10.1007/s11082-021-03399-5

Abstract

On-demand generation and reshaping of arrays of focused laser beams is highly desired in many areas of science and technology. In this work, we present a versatile approach for laser beam structuring in the focal plane of a lens by triple mixing of square and/or hexagonal optical vortex lattices (OVLs). In the artificial far field the input Gaussian beam is reshaped into ordered arrays of bright beams with flat phase profiles. This is remarkable, since the bright focal peaks are surrounded by hundreds of OVs with their dark cores and two-dimensional phase dislocations. Numerical simulations and experimental evidences for this are shown, including a broad discussion of some of the possible scenarios for such mixing: triple mixing of square-shaped OVLs, triple mixing of hexagonal OVLs, as well as the two combined cases of mixing square-hexagonal-hexagonal and square-square-hexagonal OVLs. The particular ordering of the input phase distributions of the OV lattices on the used spatial light modulators is found to affect the orientation of the structures ruled by the hexagonal OVL. Reliable control parameters for the creation of the desired focal beam structures are the respective lattice node spacings. The presented approach is flexible, easily realizable by using a single spatial light modulator, and thus accessible in many laboratories.

Highlights

Ever since their discovery (Nye and Berry 1974), optical vortices have been subject of intense research interest
The results presented in this paper for triple mixing of square-shaped and hexagonal optical vortex (OV) lattices substantially expand previous published works and are clear manifestations for the possibility to create a rich variety of focal arrays composed of bright beams
When hexagonal OV lattices are involved in the triple mixing, an additional control parameter can be used

Summary

Introduction

Ever since their discovery (Nye and Berry 1974), optical vortices have been subject of intense research interest. Due to their characteristic screw phase profiles, they are the only known truly two-dimensional (2-D) phase singularities. The phase at the singularity point of an optical vortex (OV) is not defined and, the intensity must vanish, leading to a doughnut-shaped bright beam (Rozas et al 1997a; Desyatnikov et al 2005). It is referred to as the topological charge (TC) m, i.e. an integer number with sign, describing the total phase change 2 m around the OV beam axis in azimuthal direction. The entire physical picture is far richer, we will restrict our analysis to the canonical phase vortices, whose phase changes linearly in azimuthal direction

Methods

Results

Conclusion