Highly efficient hybrid fiber taper coupled microsphere laser

Summary form only given. High Q dielectric microcavities, in which light is trapped internally as whispering gallery mode (WGM) resonances, have attracted interest in applications as diverse as quantum optics and optical communications. Among these, rare-earth doped glass microsphere lasers have been demonstrated as potentially compact laser sources. We recently presented a fiber-taper coupled microsphere laser in the 1550-nm band, which exhibited efficient fiber to sphere coupling and the advantages of fiber compatibility. In this paper, we propose a novel hybrid-fiber-taper based laser coupling configuration, in which the microsphere is coupled using a single fiber taper that is a combination of 980-nm single mode fiber (SMF) and 1550-nm SMF. The pump source and the laser emission are then both guided in single mode fiber to or from the taper region. This structure has greatly improved the coupling of the fundamental pump mode to WGMs of the microsphere. In addition, the measured laser output power of 112-/spl mu/W is over an order of magnitude larger than our previous result. The differential quantum efficiency has been measured to be 12%.