Enhanced detection techniques of Orbital Angular Momentum states in the classical and quantum regimes

TL;DR

This paper introduces an improved method for detecting and classifying Orbital Angular Momentum states of light by employing Hypergeometric-Gaussian modes, leading to enhanced detection efficiency and better alignment with experimental conditions in quantum applications.

Contribution

The study develops a refined detection model using Hypergeometric-Gaussian modes, surpassing traditional Laguerre-Gauss-based methods, and demonstrates significant improvements in detection performance and efficiency.

Findings

Three-fold increase in single-mode fiber coupling efficiency.

Enhanced detection performance with holographic projection and machine learning.

Better alignment with experimental OAM generation methods.

Abstract

The Orbital Angular Momentum (OAM) of light has been at the center of several classical and quantum applications for imaging, information processing and communication. However, the complex structure inherent in OAM states makes their detection and classification nontrivial in many circumstances. Most of the current detection schemes are based on models of the OAM states built upon the use of Laguerre-Gauss modes. However, this may not in general be sufficient to capture full information on the generated states. In this paper, we go beyond the Laguerre-Gauss assumption, and employ Hypergeometric-Gaussian modes as the basis states of a refined model that can be used -- in certain scenarios -- to better tailor OAM detection techniques. We show that enhanced performances in OAM detection are obtained for holographic projection via spatial light modulators in combination with single-mode fibers, and for classification techniques based on a machine learning approach. Furthermore, a three-fold enhancement in the single-mode fiber coupling efficiency is obtained for the holographic technique, when using the Hypergeometric-Gaussian model with respect to the Laguerre-Gauss one. This improvement provides a significant boost in the overall efficiency of OAM-encoded single-photon detection systems. Given that most of the experimental works using OAM states are effectively based on the generation of Hypergeometric-Gauss modes, our findings thus represent a relevant addition to experimental toolboxes for OAM-based protocols in quantum communication, cryptography and simulation.