Generalized laws of refraction and reflection at interfaces between different photonic artificial gauge fields

Artificial gauge fields the control over the dynamics of uncharged particles by engineering the potential landscape such that the particles behave as if effective external fields are acting on them. Recent years have witnessed a growing interest in artificial gauge fields generated either by the geometry or by time-dependent modulation, as they have been enablers of topological phenomena and synthetic dimensions in many physical settings, e.g., photonics, cold atoms, and acoustic waves. Here, we formulate and experimentally demonstrate the generalized laws of refraction and reflection at an interface between two regions with different artificial gauge fields. We use the symmetries in the system to obtain the generalized Snell law for such a gauge interface and solve for reflection and transmission. We identify total internal reflection (TIR) and complete transmission and demonstrate the concept in experiments. In addition, we calculate the artificial magnetic flux at the interface of two regions with different artificial gauge fields and present a method to concatenate several gauge interfaces. As an example, we propose a scheme to make a gauge imaging system-a device that can reconstruct (image) the shape of an arbitrary wavepacket launched from a certain position to a predesigned location. Photonics: Manipulating light with artificial fieldsArtificial gauge fields are a technique to engineer the potential landscape such that neutral particles mimic the dynamics of charged particles driven by external fields. Researchers in Israel and Germany, led by Mordechai Segev at Technion Israel Institute of Technology, and Georg von Freymann from the University of Kaiserslautern, Germany, and their students Moshe-Ishay Cohen and Christina Joerg, studied theoretically and experimentally what happens when waves are incident at the interface between two photonic systems made from the same material, with the only thing making them different being their artificial gauge fields. The team formulated the generalized laws of refraction and reflection at such gauge interfaces, and demonstrated the concepts with micro-printed waveguides arrays with different tilt angles. The research demonstrates that several interfaces between regions with differing gauge fields could be used to develop novel photonic devices.