Deep‐UV Photonic Crystal Surface‐Emitting Lasers

Abstract 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 (<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 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.