ERBIUM-DOPED GLASSES FOR FIBER AMPLIFIERS AT 1500-NM

The importance of the host glass composition has been recognized from the earliest days of fiber lasers and amplifiers. Material-dependent properties influencing the performance of fiber amplifiers are reviewed together with the available data for Er-3+. The major glass types potentially useful in this application are considered and compared to silica. The topics addressed include quenching processes and the solubility of rare-earth ions, transition strengths and bandwidths at the 1500-nm gain transition, and the characteristics at the 800-, 980-, and 1480-nm pump bands. Aluminum is shown to be an extremely useful codopant for silica, improving its ability to dissolve rare-earth ions and providing desirable spectroscopic properties for Er-3+. For some of the attributes considered, other glasses have advantages over Al silica, but only with respect to gain bandwidth and pumping at 800 nm is significantly better performance expected from other glass compositions.