Non‐Hermitian Topological Lattice Photonics: An Analytic Perspective

Topological lattice photonics leverages concepts from condensed matter physics to engineer robust light propagation in photonic systems. It relies upon foundational models that stem from mathematical equivalence between electronic and photonic systems. This review analyzes three prototypical models—the non‐Hermitian Hatano–Nelson (HN), Su–Schrieffer–Heeger (SSH), and generalized Rice–Mele (RM) models—and addresses their experimental realizations in 1D/2D photonic platforms. The non‐Hermitian HN model exemplifies non‐Hermitian skin effects, where bulk states localize at boundaries due to nonreciprocal couplings, yielding unidirectional transport and enhanced sensing. The underlying point‐gap topology of these effects is revealed by analytical solutions for 1D/2D lattices, as experimentally corroborated in laser arrays. The non‐Hermitian SSH model demonstrates topological edge states and bulk‐boundary correspondence, with 2D extensions hosting skin‐topological edge states that merge the skin effect and topology and higher‐order corner states that feature enhanced intensity. The non‐Hermitian RM model incorporates spin–orbit coupling and staggered potentials, enabling spin‐polarized edge states and dual bulk‐boundary correspondence, where distinct topological invariants govern spin‐up and spin‐down modes. Through the synergy of condensed matter theory and photonic engineering, this field unlocks potential for disorder‐immune lasers, ultrasensitive detectors, quantum light sources, and reconfigurable optical circuits.