Low threshold fiber taper coupled rare earth ion-doped chalcogenide microsphere laser

We report the applications of a low-cost and environmentally friendly chalcogenide glass, 75GeS₂-15Ga₂S₃-10CsI, in building active microsphere laser oscillators. A silica fiber taper is used as the coupling mechanism. With an 808-nm laser diode as a pump source, we show that a high-Q (～ 6×10⁴) laser mode could be obtained from a 75-μm diameter microsphere that is coupled with a 1.77-μm waist-diameter fiber taper. The threshold of the incident pump power is 1.39 mW, which is considerably lower than those of previously reported free-space coupled chalcogenide microsphere lasers. We also note an apparent enhancement in laser power generated from this chalcogenide microsphere laser.