Ultraviolet laser emission observed from gallium nitride vertical-cavity structure
A gallium nitride (GaN) based vertical-cavity surface-emitting laser (VCSEL) has been demonstrated with surface emission near 363 nm at room temperature. The device was pumped with the 337-nm output of a nitrogen laser along a cleaved sample edge. Researchers from Advanced Technology Materials (Danbury, CT) and the University of Massachusetts (Amherst, MA) believe this is the first laser action in a GaN-based vertical-cavity structure.
The VCSEL structure was grown on a sapphire substrate by metal-organic vapor-phase epitaxy and consists of a 10-?m GaN active region sandwiched between 30-period Al0.40Ga0.60N/Al0.12Ga0.88N Bragg reflectors. At optical pum¥intensities greater than about 2.0 MW/cm2, a narrow laser mode at 363.5 nm emerges from the GaN photoluminescence spectrum. At higher pum¥powers, this mode becomes the dominant feature of the spectrum, and additional modes appear at about 1.3 nm above and below this mode. Commenting on their results, the researchers note that this mode spacing is consistent with expectations for the VCSEL structure based on an electromagnetic model.