Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes

TL;DR

This paper introduces a novel spiral optical transformation that significantly improves the resolution of orbital angular momentum mode sorting in optical systems, enabling more precise and efficient separation of vortex modes.

Contribution

The authors propose and experimentally verify a new spiral-based optical transformation that surpasses traditional methods by providing higher resolution in mode sorting without sacrificing efficiency.

Findings

Achieved higher resolution in vortex mode sorting.

Maintained 100% efficiency in the transformation.

Validated the approach through experimental verification.

Abstract

Mode sorting is an essential function for optical systems exploiting the orthogonality of photonic orbital angular momentum mode space. The familiar log-polar optical transformation provides an efficient yet simple approach, however with its resolution restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along one complete circle around the optical vortex axis that is transformed into a line segment with finite length. We propose and experimentally verify a new optical transformation that maps spirals instead of closed concentric circles to parallel lines. As the phase excursion along a spiral in the transverse plane of orbital angular momentum modes is theoretically unlimited, this new optical transformation separates vortex modes with superior resolution while maintaining unity efficiency.