Topologically Protected Single Edge Mode Lasing in Photonic Crystal Su–Schrieffer–Heeger Lattice with Directional Loss Control

Abstract

Topological photonics is considered to be a robust and flexible platform for the design of nanophotonic devices against structural imperfections and performance degradation. Combining with parity-time (PT) symmetry systems based on spatially distributed gain and loss, photonic crystal (PhC) lasers with micron-size carrier reservoirs offer an ideal test bed for lasing mode competition and topological protection in nanophotonic structures. In this study, single topological edge mode (TEM) lasing is demonstrated in PhC lasers with a Su–Schrieffer–Heeger lattice comprised of coupled nanoresonators. By inducing directional loss control, a mode selection strategy is implemented, that achieves single TEM lasing with a side-mode-suppression ratio exceeding 30 dB. One of the TEMs exhibits remarkable robustness against local potential variation introduced by additional loss channels. This strategy integrating both topological protection and PT symmetry in nanophotonics would open up new prospects for the development of on-chip single-mode topological lasers unperturbed by output channels in nanophotonic integrated circuits.