Performance-enhanced single-mode microlasers in an individual microwire covered by Ag nanowires

Abstract

Developing miniaturized microlasers with higher monochromaticity and better beam quality is crucial importance because of their tremendous potential in commercial applications. Among various experimental schemes, reducing the microlaser size has always been accepted as the simplest approach to obtaining single-mode operation, but such modulation is impeded by unfavorable factors including higher threshold, lower cavity quality and poorer laser beam quality. In the present research, we realized a stable single-mode microlaser in an individual ZnO microwire via Ga-incorporation (ZnO:Ga MW), with the laser performances enhanced using Ag nanowires decoration. The ZnO:Ga MWs with hexagon-shaped cross-sectional profiles can function as optical cavities and support whispering gallery mode (WGM) lasing. By comparing the bare ZnO:Ga wire, the single-mode microlaser exhibited a lower threshold of 137.7 kW/cm2 and a higher Q-factor value of about 2428 profiting from the covered Ag nanowires. A possible working principle was herein proposed that the ultraviolet plasmons derived from Ag nanowires might play a crucial influence on the enhanced laser performances. First, the enhancement in lasing intensity is ascribed to the coupling between Ag nanowires plasmons and ZnO:Ga excitons. Second, the spatially strengthened electric field around the pentagonal edges of Ag nanowires can tremendously increase the total internal-wall reflection of hexagon-shaped wire WGM microresonator, thus contributing to the increase of cavity quality. The results illustrated that the promising potentials of high-performance single-mode microlasers are much desirable for realistic applications in highly integrated optoelectronic devices, especially for the potential fabrication of electrically pumped micro/nanolaser devices.