Highly efficient hybrid fiber taper coupled microsphere laser

Abstract

A novel hybrid fiber taper is proposed and demonstrated as the coupler in a microsphere laser system. The pump wave and the laser emission, respectively, are more efficiently coupled to and from the sphere modes with this taper structure. A 980-nm pumped erbium–ytterbium codoped phosphate microsphere laser is demonstrated in the 1550-nm band. As much as $112 \mu \mathrm{W}$ of single-frequency laser output power was measured, with a differential quantum efficiency of 12%.