Effective Sorting of Fractional Optical Vortex Modes

TL;DR

This paper introduces a novel method for effectively sorting fractional optical vortex modes by transforming them into integer modes and then sorting, enhancing capabilities for high-capacity optical communication systems.

Contribution

The paper presents a new coordinate transformation approach to sort fractional OAM modes, extending existing integer mode sorting techniques to fractional modes.

Findings

Successfully demonstrated fractional mode sorting experimentally.

Achieved high mode purity in the sorting process.

Potential to enable high-capacity, secure optical communication.

Abstract

Mode sorter is the crucial component of the communication systems based on orbital angular momentum (OAM). However, schemes proposed so far can only effectively sort integer OAM (IOAM) modes. Here, we demonstrate the effective sorting of fractional OAM (FOAM) modes by utilizing the coordinate transformation method, which can convert FOAM modes to IOAM modes. The transformed IOAM modes are subsequently sorted by using a mode conversion method called topological charge matching. The validation of our scheme is verified by implementing two sorting processes and corresponding mode purity analyses, both theoretically and experimentally. This new sorting method exhibits a huge potential of implementing a highly confidential and high-capacity FOAM-based communication system, which may inspire further applications in both classical and quantum regimes.