High-power microcavity lasers based on highly erbium-doped sol–gel aluminosilicate glasses

High-power whispering-gallery-mode (WGM) lasing from highly erbium-doped sol–gel aluminosilicate microsphere cavity coupled to a half-tapered optical fiber is presented. The lasing output power as high as 0.45 mW (−3.5 dBm) was obtained from sol–gel glass microsphere cavity with diameters in the range of 40–150 μm. The sol–gel method for making highly concentration Er-doped aluminosilicate glasses with Er-ion concentrations from 0.125 to 0.65 mol% of Er3+ is described. Controlling collected lasing wavelength at each WGM is possible by adjusting the distance between the half-taper fiber and the microcavity and by diameter of the waist of half-taper fiber. Using the analytic formulas we calculated the TE and TM lasing modes and it is shown that the experimental results are in good agreement with the calculation prediction.