The exploitation of non-Hermitian quantum physics concepts in classical photonics has spawned much research activity during 2017. We conclude the year with a focus issue on parity–time symmetry and concepts with overlapping goals, in particular topological and non-reciprocal photonics.
The exploration of photonic systems embracing the concepts of PT symmetry, topology and non-reciprocity has become highly active in recent years. Studies on these topics are not only providing rich scientific insight in terms of new physics but also potentially have important long-term technological implications, including the development of on-chip optical systems that support states of light that are immune to back scatter, are robust against perturbation and feature guaranteed unidirectional transmission.
Nature Photonics spoke to Demetrios Christodoulides, of CREOL, The College of Optics & Photonics, University of Central Florida, about the birth of the parity–time-symmetry concepts in optics and the challenges and prospects on the path ahead.
General concepts and recent developments of parity–time symmetry in classical photonics are reviewed.
Topological photonic structures offer unique features such as reflection-free and non-reciprocal devices. This Review highlights the experimental progress in the relatively new field of photonic topology.
The progress on non-reciprocal photonic devices enabled by temporal modulation is reviewed.