We report ultraviolet (UV) whispering-gallery-mode (WGM) lasing in a zinc oxide (ZnO) micro/nanosphere crystal fabricated by simply ablating a ZnO sintered target, which was much more productive method without any time-consuming crystal-growth process. The lasing spectral mode spacing was controlled by changing the diameters, and single-mode lasing was realized from a ZnO nanosphere. Experimental results were in good agreement with predictions from WGM theories. Since the ZnO sphere can operate as an active WGM refractometric sensor for small molecules in UV region, high sensitivity enhanced by high quality factor, refractive index, and wavelength dispersion can be expected.

We report ultraviolet electroluminescence from a hetero p-n junction between a single ZnO microsphere and p-GaN thin film. ZnO microspheres, which have high crystalline quality, have been synthesized by ablating a ZnO sintered target. It was found that synthesized ZnO microspheres had a high-optical property and exhibit the laser action in the whispering gallery mode under pulsed optical pumping. A hetero p-n junction was formed between the single ZnO microsphere/ p-GaN thin film, and a good rectifying property with a turn-on voltage of approximately 6 V was observed in I-V characteristic across the junction. Ultraviolet and visible electroluminescence were observed under forward bias.

No abstract

We succeeded in synthesizing ZnO microspheres by a simple atmospheric laser ablation method. The ZnO microsphere has a completely spherical in shape, and a whispering gallery mode lasing from the microsphere was observed.

Zinc oxide (ZnO) nano/microstructures have been attractive as the building blocks for the efficient opto-electronic devices in the ultraviolet (UV) region. We have succeeded in growing the ZnO micro/nanosphere by a simple laser ablation in the air, and therefore we have obtained UV lasing from the sphere under optical pumping. Recently, large size of several 10 micrometer ZnO microspheres were grown using Nd:YAG laser without Q-switching, and ZnO microsphere/p-GaN heterojunction were fabricated to obtain the electroluminescence (EL) from the microsphere by electrical pumping. Room-temperature EL in near-UV region with peak wavelength of 400 nm is observed under forward bias.