Advances on Topological Photonics in Non‐Hermitian, Spatial‐Temporal, Nonlinear, and Quantum Regimes

ABSTRACT

Topological photonics has emerged as a versatile platform for exploring robust wave phenomena by translating concepts from topological band theory into optical systems. Early developments focused on photonic analogues of topological insulators, where protected edge states enable disorder‐immune light transport and robust photonic devices. These foundational studies, realized in photonic lattices, established topological protection as a practical design principle for optical routing, lasing, and light‐matter interfaces. Recent advances have expanded this field far beyond its original Hermitian and static framework. Non‐Hermitian photonic systems, incorporating gain, loss, and radiation, have revealed complex spectral topologies, exceptional points, and unconventional bulk‐boundary correspondence. Time‐modulated and spatiotemporal structures introduce Floquet engineering, momentum‐gap topology, and temporal boundary states, positioning time as an active topological dimension. Meanwhile, nonlinear photonic platforms enable interaction‐driven topological phenomena, including solitons and self‐induced phase transitions, while quantum topological photonics provides robust channels for single photons and light‐matter entanglement. Together, these developments mark a transition from static band topology to a broader paradigm of driven, open, nonlinear, and quantum topological photonic matter, establishing topological photonics as a unified platform, for both fundamental physics and next‐generation optical technologies.