Room-temperature excitonic lasing in ZnO tetrapod-like crystallites

Room-temperature low-threshold (0.55 mJ/cm2) lasing in UV-region was observed in ZnO powders with tetrapod-like shape of crystallites. Zinc oxide powders were prepared by high-temperature pyrolysis of zinc-containing organic salts. The lasing characteristics were stable and reproducible from pulse to pulse and varied from point to point on the sample surface due to random displacement of crystallites on the sample surface and the dispersion of the crystallite sizes. The lasing spectra were characterized by clear mode structures, the full width of lasing lines at half maximum being equal to ∼0.2 nm. The main characteristics of the lasing spectra indicated that we observed the lasing from single ZnO tetrapod working as high-Q microcavity (microlaser).