Single-mode lasing based on PT-breaking of two-dimensional photonic higher-order topological insulator

Topological lasers are a new class of lasers that seek to exploit the special properties of topological states of light. A typical limiting factor in their performance is the existence of non-topological states with quality factors comparable to the desired topological states. We show theoretically that, by special design of uniform gain and loss on two sublattices of a two-dimensional higher-order topological insulator (HOTI) lattice, single-mode lasing based on topological corner states can be sustained over a wide dynamic range of laser. This behavior stems from the phenomenon of parity/time-reversal breaking of the topological corner states, where the undesired edge and bulk states are suppressed much more effectively than through localized pumping of the domain corners. These promising results shed light on the opportunities for exploiting non-Hermitian phenomena in the design of high performance topological lasers with small footprint.