Topological lasers

Recently, we have demonstrated novel lasers which exploit the topological properties of the photonic band structure to control the scaling and emission profile of semiconductor lasers. Among them are topological lasers based on the quantum-hall and valley-hall effects. These laser cavities rely on feedback from edge-modes that are robust to disorders and can produce vortex beams with orbital angular momentum. We also developed the first bound state in the continuum (BIC) laser which can minimize the threshold for small cavities and investigated their viability for electrical injection. Due to the properties of this topological singularity, lasers operating at BIC modes can be optimized for both small and large scale apertures. In this talk, we will focus on the scaling of photonic crystal lasers with increasing cavity size. The influence of the symmetry of the modes and the coupling between Bloch bands on the lasing response will also be discussed. Finally, we conclude by introducing a scheme that can improve the threshold gain difference between the fundamental and higher-order modes and enable single-mode lasing in large-scale photonic crystal lasers.