Sub-microwatt lasing of whispering gallery mode microcavities functionalized with lanthanide oxide nanoparticles

The author presents the significant improvement on lowest laser threshold for a rare-earth based microlaser from the previous work of Sandoghdar et. al (1996), achieving values down to 40 nW. Beside the unique properties of whispering gallery mode (WGM) silica microcavities, this progress relies on the use of lanthanide oxide nanoparticles (NP) for their functionalization. It also takes advantage of some techniques that the authors have recently introduced.