Transcoder for the spatial and temporal modes of a photon

TL;DR

This paper presents a photonic transcoder that converts light carrying orbital angular momentum into Gaussian time-bin pulses and vice versa, enabling compatibility between high-capacity OAM channels and fiber transmission.

Contribution

The authors experimentally realize a scalable photonic space-time transcoder that preserves coherence and minimizes cross-talk between modes, bridging OAM and Gaussian modes for optical communication.

Findings

Successfully converts OAM superpositions into Gaussian time-bin pulses

Demonstrates coherence preservation and low cross-talk between modes

Enables integration of OAM-based and fiber-optic communication systems

Abstract

Encoding information in light with orbital angular momentum (OAM) enables networks to increase channel capacity significantly. However, light in only the fundamental Gaussian mode is suitable for fibre transmission, and not higher order Laguerre Gaussian modes, which carry OAM. Therefore, building a bridge to interface light with OAM and Gaussian mode time-binning is crucially important. Here, we report the realization of a photonic space-time transcoder, by which light with an arbitrary OAM superposition is experimentally converted into a time-bin Gaussian pulse, and vice versa. Furthermore, we clearly demonstrate that coherence is well conserved and there is no cross-talk between orthogonal modes. This photonic device is simple and can be built with scalable architecture. Our experimental demonstration paves the way towards a mixed optical communication in free-space and optical fibre.