Doped microspheres for whispering gallery mode microlasing

Whispering gallery mode(WGM)optical microcavities,which are capable of light field confinement and manipulation in a relatively small volume,have gained considerable attention from fundamentals in enhanced light-matter interactions to laser applications[1].Undergoing decades of development,the improvement of lasing performance is always a significant issue,including low threshold and high quality(Q)factor[2].Increasing optical gain and reducing the losses are the key aspects towards the realization of a high-quality WGM laser.A perfect cavity structure and a smooth surface are the most crucial determinants to reduce optical losses and enhance light field confined abilities.