Non-reciprocity and and non-reciprocal effective gauge field in dynamically modulated photonic structures

In photonics, the capability to break time-reversal symmetry or reciprocity in electromagnetic wave propagation is important both from a practical and from a fundamental view point. From a practical point of view, non-reciprocal devices are widely used to achieve signal isolation that is crucial for the performance and scalability of large-scale optical networks. One of the long standing challenges in integrated photonics has been to create non-reciprocal devices on-chip. We show that dynamic modulation of photonic structure provides a natural and practical way to achieve on-chip non-reciprocal devices. From a fundamental point of view, breaking time-reversal symmetry results in a wide variety of physical effects that cannot be observed in reciprocal structures. We show that the use of dynamic modulation can result in the creation of an effective gauge potential and gauge field for photons, leading to novel effects such as Lorentz force for photons, and one-way edge state that is a direct analogue of the electronic quantum Hall effect.