Ultraviolet Lasing Phenomenon of Zinc Oxide Hexagonal Microtubes

Prismatic zinc oxide (ZnO) hexagonal microtubes have been fabricated on silicon substrate using vapor transport. Two morphologies, bell-mouthed and uniform hexagonal microtubes, are obtained from the fabrication process. The ZnO hexagonal microtubes have demonstrated ultraviolet (∼393 nm) lasing emission under 355 nm optical excitation. It is found that the threshold pump intensity and cavity mode spacing of the microtube lasers are ∼500 kW/cm 2 and ∼0.7 nm, respectively. The lasing characteristics of the microtube lasers are also investigated. It is shown that high threshold pump intensity of the microtube lasers is due to the high radiation loss arising from the hollow hexagonal structure near the prismatic facets.