  Erbium-doped lithium niobate high-Q microdisk cavities were fabricated in
batches by UV exposure, inductively coupled plasma reactive ion etching and
chemo-mechanical polishing. The stimulated emission at 1531.6 nm was observed
under the pump of a narrow-band laser working at 974 nm in erbium-doped lithium
niobate microdisk cavity with threshold down to 400 {\mu}W and a conversion
efficiency of 3.1{\times}10^{-4} %, laying the foundation for the LNOI
integrated light source research.
