Whispering-gallery mode lasing in ZnO microcavities

Abstract

Zinc oxide (ZnO) is considered as an ideal candidate for ultraviolet (UV) lasers due to its unique advantages of wide direct bandgap and large exciton binding energy. Recently, whispering-gallery mode (WGM) lasing has attracted considerable attention for its high quality factor and low lasing threshold. The corresponding investigations have very important significance not only for fundamental scientific research but also for the potential applications in short-wavelength optoelectronic devices. In this paper, progress in ZnO microlasers is reviewed systematically. The fabrication methods for ZnO WGM microcavities are introduced first. Then the characteristics of single-photon and multiphoton pumped WGM lasing are presented. The lasing mechanisms on excitonic, electron-hole plasma and exciton-polariton lasing are reviewed in detail. Finally, recent advances in ZnO-based microlaser devices such as heterojunction laser diodes are explored. The further research challenges and some strategies are also indicated for the promising applications. © 2014 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.