High Fidelity Detection of the Orbital Angular Momentum of Light by Time Mapping

TL;DR

This paper presents a compact, high-fidelity method for detecting the orbital angular momentum of light by mapping OAM states to time using a specialized spectrometer, enabling accurate measurement of complex OAM compositions.

Contribution

The authors introduce a novel OAM spectrometer that maps OAM to time, allowing precise detection of light's OAM states with high fidelity and practical implementation.

Findings

Achieved an average crosstalk of -21.3 dB for OAM up to 4ħ.

Demonstrated measurement of arbitrary OAM compositions.

The method is limited mainly by input state purity and optical alignment.

Abstract

We demonstrate high-fidelity detection of the orbital angular momentum (OAM) of light using a compact and practical OAM spectrometer that maps the OAM spectrum to time. The spectrometer consists of a single optical delay loop to achieve timing mapping, a vortex phase plate that iteratively decreases the OAM value, and a single mode fibre to distinguish zero from non-zero OAM states. Light with arbitrarily OAM compositions can be measured. For light with OAM up to 4hbar, we measured an average crosstalk of -21.3 dB, which is mainly limited by the purity of the input states and optical alignment.