Optical performance improvement in hydrothermal ZnO/graphene structures for ultraviolet lasing

Abstract

Ever since the exploration of ZnO for ultraviolet (UV) lasers, realization of high performance lasing in hydrothermal samples is still a challenge due to the poor crystal quality. In this paper, high quality ZnO microcavities were fabricated by a hydrothermal method with graphene as a growth medium. The structural, optical as well as the exciton dynamic properties were studied systematically. Compared with the one grown without graphene, structured cavity morphology, higher light emission intensity and faster exciton recombination dynamics process were observed for ZnO grown on graphene, which make the ZnO samples suitable for lasing. When it was excited by a 325 nm femtosecond laser, single mode lasing with a central wavelength of about 393.2 nm and a Q value of about 936 was realized in a vertical cavity. By further increasing the exciton recombination rate through Al decoration, intensity improved multimode lasing was realized. Our results propose a strategy for yielding single mode lasers in several micrometers with improved performances.