General photonic-crystal slab cavity design for scalable high-power single-mode lasing

Scaling up the area of photonic-crystal surface-emitting lasers (PCSELs) to produce higher output power while maintaining single-mode operation has been a longstanding objective in photonics and laser physics. Achieving this goal requires two fundamental physics: the difference between the modal losses of the fundamental and higher-order modes, and the mode competition between them. Both physics contribute to the lasing threshold difference between the fundamental and higher-order modes and have been considered individually in past works. But there has not been a theoretical study that treats both physics together for the design of PCSELs. Here we provide a theoretical framework to elucidate the interplay between differential modal losses and mode competition in PCSELs. Based on this framework, we introduce designs based on spatial engineering of photonic-crystal slabs to simultaneously control the modal properties and mode competition. Compared to designs that focus on only one of these physics, our designs can increase the difference between the lasing thresholds of the fundamental and higher-order modes by orders of magnitude. Our findings provide new insights into realizing scalable PCSELs for large-area single-mode lasing.