Investigation of the ultraviolet lasing characteristics of zinc hexagonal microtubes

Prismatic zinc oxide (ZnO) hexagonal microtubes have been fabricated on silicon substrate by vapor transport. It is shown that the ZnO hexagonal microtubes have demonstrated ultraviolet (∼393 nm) lasing emission under 355 nm optical excitation. Furthermore, the lasing as well as modal characteristics of the microtube lasers are investigated theoretically. It can be explained that the high threshold pump intensity of the microtube lasers is due to high radiation loss near the prismatic facets. In addition, our calculation has shown that the output beam from the microtube lasers has a shape similar to the doughnut ring, which can find application as laser tweezers to trap low refractive index small particles.