  We have demonstrated an ultrahigh-Q whispering-gallery-mode (WGM) microsphere
laser based on the evanescent-wave-coupled gain. Dye molecules outside the
sphere near the equator were excited, resulting in WGM lasing in the lowest
radial mode order. The loaded quality factor of the lasing WGM was 8(2)\times
10^9, the highest ever achieved in the microlaser.
