Based on their expansive flexibility of controlling the propagation, coupling, and confinement of light, photonic systems are a prime physical platform to realize the full potential of devices whose functionality is enhanced by symmetry and topology. Most notably, the capability to manipulate photonic eigenstates through optical gain and loss provides a powerful toolbox for tailoring non-Hermitian Hamiltonians to study symmetry paradigms that go beyond conventional condensed matter systems—marking the birth of non-Hermitian photonics. Rapid developments of these concepts over the past decade have already empowered us to achieve complex optical responses and unique light-matter interactions, in both classical and quantum domains. Despite the similarities shared with electron-based quantum systems, non-Hermitian photonics is rooted in the fundamentals of electromagnetics and governed by Bosonic statistics. The direct inclusion of optical non-Hermiticity in first-principle electromagnetic designs leads to new types of light-matter interaction that are beyond the fermionic symmetry paradigms, leading to a multitude of phenomena that have no counterpart in condensed matter and passive photonic systems. The objective of this special issue is to cover the most exciting developments in the field that enhance our fundamental understanding of quantum and optical physics and facilitate technological breakthroughs for photonic applications.
Guest Editors: Liang Feng, Minghui Lu, Li Ge, and Henning Schomerus