Fundamental understanding of Photonics leads to new on-chip manipulation of light

31 January 2014

Sydney University Photonics researchers have combined fundamental ideas of quantum mechanics with modern optical technology to build a non-reciprocal, one way, circuit for light.

By incorporating the latest developments in photonics and integrated optics being researched at CUDOS, the photon-phonon interaction demonstrated in this work could be utilised to fabricate integrated photonic devices, such as magnet-free on-chip isolators that are a critical building block for the photonic chip, which CUDOS's research is focused on.

The experimental setup
The experimental setup

Dr Enbang Li and Professor Ben Eggleton from CUDOS (ARC Centre of Excellence for Ultrahigh bandwidth Devices for Optical Systems) at the University of Sydney's School of Physics have led an international collaboration to observe the Aharonv-Bohm (AB) effect for light. The research builds on a long standing collaboration with Wollongong University, as well as Dr. Kejje Fang of Caltech, and Prof. Shanhui Fan at Stanford University, and appears in Nature Communications on January, 2014.

"We have demonstrated both theoretically and experimentally that by using the interactions between photons and phonons (acoustic waves), we can introduce non-reciprocal phase shift to photons" said Dr Li

The results presented here points to new possibilities to control and manipulate light by the photon-phonon interactions that can occur in different platforms, including waveguides and photonic crystals.

It's the photonics version of one way sunglasses. The person wearing the glasses can see out but others can't see in. - Professor Eggleton

In telecommunications non-reciprocity underpins devices referred to as an isolator that transmit photons in a single direction only, these isolators are essential for further photonics experiments and developments as the circuits rely on non-reciprocity.

Dr Enbang Li and Professor Ben Eggleton
Dr Enbang Li and Professor Ben Eggleton

The classical AB effect is well understood for charged particles such as electrons but has not been observed for photons. The new physics in this experiment is the demonstration of the AB effect, in photons, or light.

We can't do better than our results!- Dr Li.

This breakthrough demonstrates that AB effects do exist for photons, or neutral particles. This was achieved by having photons interact with the material they propagate through, with acoustic waves called phonons, in such a way that renders the photons non-reciprocal.

The AB effect for charged particles is dependent on a magnetic field, which interacts with the particle. This is not the case with neutral particles, which do not interact with the magnetic field, so an experimental equivalent was produced to see the effect.

The AB effect for charged particles has applications in various fields, including quantum interference at the single-molecule level, understanding of the micro- and nano-structures and materials, and matter/wave investigations.

Read the full Nature Communications paper online at

Contact: Tom Gordon

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