Core-Shell ZnO Nanorod Lasers

Room-temperature ultraviolet lasing in [0001] oriented zinc oxide nanorods are grown on silicon and fused silica substrates by a simple vapor transport and condensation process. These wide band-gap semiconductor nanorods form natural laser cavities with diameters varying from 150 to 350 nm and lengths up to 10 mu m. Under optical excitation, surface-emitting lasing action was observed at 385 nm. The dielectric core-shell Al2O3@ZnO nanorods exhibit enhanced axial Fabry-Perot resonating characteristics with (0001) crystal faces acting as mirror facets and improved by a metallic reflector at one end. This metallic coating and dielectric oxide shell greatly increase near-band edge emission while reducing excitation power thresholds due to lower losses and increased optical density from improved refractive index mediated waveguiding during optical pumping.