Two-dimensional (2D) laser arrays are shown to be achievable at a large scale by exploiting the interplay of higher-order topological insulator (HOTI) physics and the so-called non-Hermitian skin effect (NHSE). The higher-order topology allows for the amplification and hence lasing of a single mode protected by a band gap, whereas the NHSE is introduced to compete with the topological localization of corner modes. By tuning the system parameters appropriately and pumping at only one site, a single topologically protected lasing mode delocalized across two dimensions emerges, with its power widely tunable by adjusting the pump strength. Computational studies clearly indicate that the lasing mode thus engineered is stable, and the phase difference between all lasing sites is locked at zero, even after disorder is accounted for. The total power of the designed laser array is proportional to the area of the 2D lattice accommodating a HOTI phase. Based on existing experiments, we further propose to use coupled optical ring resonators as a promising platform to realize large-scale 2D laser arrays.

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• Optics & lasers
• Topological insulators
• Topological materials