Low-Threshold Microlaser in Er : Yb Phosphate Glass Coated Microsphere

We developed a new method to fabricate a silica microsphere coated by a thin layer of Er : Yb-doped phosphate glass. The coated microsphere possessed high-Qwhispering-gallery modes and formed single-mode and multimode microlasers in the both 1550- and 1040-nm bands. A low-loss fiber taper was used to not only launch the pump power around 980 nm into the microsphere, but also collect the resulting laser emissions. In our experiment, the threshold pump power as low as 30 muW of a single longitudinal mode was obtained.