Non-Hermitian Skin Effect — Photonic Ring Array

Thirty-two photonic ring resonators sit on a circle, each coupled to its neighbours with a stronger hop clockwise than counter-clockwise — a Hatano–Nelson chain, the simplest non-Hermitian lattice. As long as the ring stays closed, that asymmetry only shows up as a topological winding number in the complex spectrum and the light stays spread evenly around the loop. Cut a single bond and the whole picture changes: every mode of the lattice, not just one, collapses exponentially onto the resonator next to the cut — the non-Hermitian skin effect. Watch the field evolve and renormalize toward its dominant mode live, toggle the boundary condition to switch the effect on and off on the same lattice, and read off the winding number, localization (skin) length and inverse participation ratio as you tune the non-reciprocity.