Deciphering cavity modes in Berkeley surface-emitting lasers (BerkSELs)

Despite the engineering advancements in the development of very large photonic crystal lasers, there has been very little progress in the development of better physics-based strategies. Our strategy employs an open-Dirac singularity related to an effective zero-index medium, enabling the existence of a flat-envelope mode. The resulting devices, called Berkeley surface-emitting lasers (BerkSELs), are uniquely characterized by this unconventional mode, effectively mitigating the spatial hole burning effect and leading to more robust single-mode emission. The device architecture enabling this new strategy consists of a photonic crystal patterned as a triangular lattice, truncated to a hexagonal shape, thus forming a finite cavity. The parameters of the photonic crystal are tuned to create an accidental degeneracy forming an open-Dirac singularity. We indicate the properties of the linear band structure that are present in the finite system and enable the in-principal scale invariance of the BerkSEL. In conclusion, this work augments our comprehension in the physics of this newly discovered flat-envelope mode in BerkSELs, shedding light on its role in achieving scale-invariant single-mode operation in photonic crystal lasers. The insights gained from our investigation hold considerable promise for transformative progress in laser technology, unlocking diverse applications in optical communication, sensing, and quantum photonics.