  We report on the fabrication of three-dimensional (3D) high-Q whispering
gallery microcavities on a fused silica chip by femtosecond laser
microfabriction, enabled by the 3D nature of femtosecond laser direct writing.
The processing mainly consists of formation of freestanding microdisks by
femtosecond laser direct writing and subsequent wet chemical etching. CO2 laser
annealing is followed to smooth the microcavity surface. Microcavities with
arbitrary tilting angle, lateral and vertical positioning are demonstrated, and
the quality (Q)-factor of a typical microcavity is measured to be up to
1.07x10^6, which is currently limited by the low spatial resolution of motion
stage used during the laser patterning and can be improved with motion stages
of higher resolutions.
