  Microlaser with multiple lasing bands is critical in various applications,
such as full-colour display, optical communications and computing. Here, we
propose a simple and efficient method for homogeneously doping rare earth
elements into a silica whispering-gallery-mode microcavity. By this method, we
demonstrate simultaneous and stable lasing covering ultraviolet, visible and
near-infrared bands in an ultrahigh-Q (exceeding 108) Er-Yb co-doped silica
microsphere under room temperature and continuous-wave pump for the first time.
The lasing thresholds of the 380, 410, 450, 560, 660, 800, 1080 and 1550
nm-bands are estimated to be 380, 150, 2.5, 12, 0.17, 1.7, 10 and 38 {\mu}W,
respectively, where the lasing in the 380, 410 and 450 nm-bands by Er element
have not been separately demonstrated under room temperature and
continuous-wave pump until this work. This ultrahigh-Q doped microcavity is an
excellent platform for high-performance multi-band microlasers,
ultrahigh-precise sensors, optical memories and cavity-enhanced light-matter
interaction studies.
