A Taper-Fused Microspherical Laser Source

We report on the realization of an integrated lasing device consisting of a microsphere optical resonator fused to a tapered optical fiber. A microsphere fabricated from Er : Yb-codoped phosphate glass is heated above its glass transition temperature of 375 $^\circ$C by pumping it at 977 nm with 70 mW via a tapered optical fiber. The onset of thermal stress in the glass at a maximum pumping power results in the sphere melting and fusing to the taper coupler, without inhibition of whispering gallery mode lasing. A taper-fused microsphere laser with $\sim$ 4.5 $\mu$W of lasing power at 1593 nm is demonstrated.