Lead silicate glass microsphere resonators with absorption-limited Q

We report the fabrication and characterization of a lead-silicate glass microsphere resonator. We show that at the wavelengths near 1555 nm high Q modes can be efficiently excited from a 109 μm diameter lead-silicate glass microsphere via evanescent coupling using a tapered silica fiber with a waist diameter of 2 μm. Resonances with Q -factors as high as 0.9× 10 ⁷ were observed. This is very close to the theoretical material-limited Q -factor and is the highest Q -factor reported so far from a nonlinear glass microsphere.