A short paper on nonlinear science, co-authored by School of Physics academic and a recently graduated student has been published in the April 18 issue of Royal Society Open Science. Open Science, launched in 2014, is an open access peer-reviewed journal that publishes research from across the entire spectrum of science and mathematics is published by the world’s oldest scientific publisher, The Royal Society of London.

“Advances in synthetic gauge fields for light through dynamic modulation” was co-authored by Dr Enbang Li, and by Daniel Hey, who graduated last year with first class honours in Physics from the University of Wollongong. The paper was written as part of a Phys 457 research project in 2017.

Head of School, Professor Michael Lerch, described the joint article as “impressive” and a good example of the valuable collaborations that frequently develop among faculty and students within the School of Physics.

“Daniel was an outstanding student here, and I am very happy that he will be recognised for this work,” Li said.


Paper Overview

This review article is based on Daniel’s Honours thesis project.  It is related to one of the most advanced research areas in photonics, called topological photonics, and one of the most fundamental problems in physics, that is, how to create the non-reciprocity or break the time reversal symmetry. In 2012, our research collaborators from Stanford University theoretically proposed that when the refractive index of a photonic system is modulated, the phase of the refractive index modulation represents a gauge potential for photons and is nonreciprocal (Phys. Rev. Lett.108, 153901; doi:10.1103/PhysRevLett.108.15 3901). In 2014, we successfully introduced nonreciprocal phases for photons and experimentally observed a gauge potential for photons in the visible range by using the photon-phonon interactions in acousto-optic crystals (. Nat. Commun.5, 3225; doi:10.1038/ncomms4225). For the first time, we also demonstrated the photonic Aharonov–Bohm effect.

Dr Enbang Li


Light obeys a fundamental principle called reciprocity, which is the idea that if light can travel in one direction it can travel in the other direction just as easily. Almost everyone is familiar with this concept: if you are to look at someone, you would expect they could also see you. One of the ultimate goals of photonics is to build tiny devices that break reciprocity – something that allows light to travel in one direction while suppressing backwards propagation. In my thesis, I looked at designing and simulating non-reciprocal devices based on the concept of dynamic modulation, where the material that light is travelling through is modified while the light is still inside it. Since the properties of light depend on the material it’s travelling through, by changing the material in just the right way you can make light do all sorts of tricks. One of these tricks is making light act like an electron would under the influence of a magnetic field, allowing us to trap light, move it in one direction only, or even dance a little jig. My paper reviews the essentials behind this theory and discusses applications outside of just non-reciprocal devices, including applications in the burgeoning field of topological photonics.


Daniel Hey

The full paper can be found on the Royal Society Open Science website.