Deep-UV Photonic Crystal Surface-Emitting Lasers

Journal article, 2025

Today's ultraviolet lasers are bulky, expensive, have low power-conversion efficiency, and usually suffer from poor beam quality. Semiconductor lasers have addressed these issues in the visible and infrared parts of the electromagnetic spectrum; but in the ultraviolet, they are just starting to see the light of day. Edge-emitting semiconductor lasers are the only ones demonstrated under electrical injection in the deep-ultraviolet ((Formula presented.) <280 nm) and they inherently suffer from poor beam qualities, multiple modes, and catastrophic optical damage to the mirror. The first deep-UV photonic crystal surface-emitting lasers are demonstrated here. The devices show single-mode emission around 279 nm with less than 1 (Formula presented.) beam divergence. They require a specific design to overcome optical scattering and the low refractive index that otherwise prohibits a 2D standing optical field. The optically pumped deep-ultraviolet photonic crystal surface-emitting lasers offer drastically improved beam quality and provide an important step toward low-divergent, watt-class, electrically-driven UV PCSELs.