Pseudospin–Orbit Coupling for Chiral Light Routings in Gauge-Flux-Biased Coupled Microring Resonators

Pseudospin–orbit coupling of light, exploiting artificially defined photon spins to steer its spatial motion, underlies many intriguing light–matter interaction phenomena and spin-based optical devices. Microring resonators, hosting counter-circulating whispering gallery modes as two pseudospins, are promising candidates for spin-based light control. Here, by applying a gauge-flux biasing in a microring resonator array with different boundary topologies, we establish a new pseudospin–orbit coupling framework and achieve spin-locked chiral light routing effects. We show that for a closed-loop array with Born–von Karman periodic boundary conditions, a real gauge-flux biasing can induce opposite dispersion relation shifting and hence clockwise and counterclockwise light routings for the two pseudospin modes. We attain spin-locked opposite routing paths both for single-port and multiport inputs using resonator trimer and quadrumer structures, respectively. For open boundary conditions, we find that an imaginary gauge-flux biasing can squeeze the two pseudospin modes to the opposite ports, showing the “non-Hermitian skin effect” and spin-locked amplified and decayed routing effects. Our study may find applications in spin-resolved networks-on-chip optical communications, interconnections, and signal processing.