OAM-mode sorting with a wavefront twister

TL;DR

This paper introduces a wavefront twister device for efficient, high-dimensional orbital angular momentum (OAM) mode sorting, improving scalability and mode separation in optical systems.

Contribution

It presents a novel wavefront twister element that generalizes wavefront rotation, enabling scalable, high-resolution OAM mode sorting with minimal overlap.

Findings

Wavefront twister maps each OAM mode to a distinct radius

The device preserves circular symmetry and minimizes inter-modal overlap

It offers a scalable approach for high-dimensional OAM mode sorting

Abstract

We propose an OAM sorter based on a novel optical element that we refer to as a wavefront twister. It is a generalization of the conventional wavefront rotators such as the Dove prism. However, unlike a Dove prism, which simply rotates a wavefront, the rotation generated by a wavefront twister varies linearly with radial position, resulting in the twisting of the wavefront. We demonstrate that the wavefront twister, followed by a lens, maps each OAM mode to an annulus of distinct radius at the back focal plane of the lens with negligible inter-modal overlap and preserves the circular symmetry. Thus, the proposed wavefront twister offers a scalable scheme for high-dimensional OAM mode sorting, with important consequences for the practical realization of OAM-based applications.