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This letter reports on long-band (L band) lasing whispering-gallery modes (WGMs) in microspheres based on sol-gel silica-alumina glasses doped with high concentration of erbium ions (Er+3 from 1250 to 15 000 ppm). The sol-gel method for making these Er-doped silica-alumina glasses is described. The microspheres with diameters from 40 to 200μm were built by electrical arc. The experimental results show that laser oscillations with high gain at L band were obtained with different coupling schemes, especially with forward pumping and/or backward pumping coupling. The collected laser output power of one WGM could reach to −5dBm in the L band of 1570–1610 nm.

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