Observation of reversible orbital angular momentum transfer based on photon-phonon coupling

TL;DR

This paper demonstrates reversible transfer of orbital angular momentum between photons and phonons using Brillouin coupling, enabling potential advancements in high-capacity optical signal processing and multiplexing.

Contribution

It introduces the first observation of controllable, reversible OAM transfer between photons and phonons via photon-phonon coupling, expanding the capabilities of signal processing schemes.

Findings

Reversible OAM transfer between photons and phonons demonstrated.

OAM and spin angular momentum are independently conserved during conversion.

Potential for extending photon-phonon signal processing with OAM multiplexing.

Abstract

Orbital angular momentum (OAM) has gained great interest due to its most attractive feature of high dimensionality, and several ground-breaking demonstrations in communication based on OAM multiplexing have been carried out. Accordingly, a rapid data-density growth from OAM multiplexing has posed a great challenge to the signal-processing layer. Meanwhile, in another area, optical signal-processing circuit based on photon-phonon conversion has received considerable attention and made rapid progress. Here, with an aim of finding the intersection between OAM multiplexing and photon-phonon conversion, we report on the observation of reversible OAM photon-phonon conversion. A specific OAM state can be flexibly and controllably interconverted between photonic and phononic domains via Brillouin photon-phonon coupling within the decay time of acoustic signal, in which OAM and spin angular momentum are independently conserved. Our result demonstrates the controllable OAM transfer between photons and phonons, shows the potential of using OAM multiplexing to extend the capacity of photon-phonon conversion based signal-processing scheme, and may trigger the development of OAM-multiplexed photon-phonon circuit.