Luminescence and laser properties of RE-doped silica optical fibers: The role of composition, fabrication processing, and inter-ionic energy transfers

Abstract

Silica glass doped with rare-earth ions remains one of the most frequently used materials for fiber lasers and amplifiers, owing to various advantages such as high thermal resistance, mechanical and chemical durability, high transparency up to 2.2 μm, and last but not least, a proven and relatively cheap technology. However, the performance of fiber lasers and amplifiers based on silica glass is limited by several drawbacks, including low solubility of rare earths, which causes a high rate of inter-ionic energy transfers processes, or high phonon energy of the silica lattice, which leads to non-radiative decay via multiphonon relaxation. Both obstacles can be countered by various strategies, with the most perspective being the addition of suitable co-dopants. The luminescence properties and laser characteristics of the final optical fiber are thus strongly dependent on the composition, as well as the fabrication processing of the material. In this review, we summarize the basic concepts and recent developments in the role of various co-dopants of rare earth ions, the fabrication processes used in the making of high-silica fibers and the inter-ionic energy-transfers, with respect to their influence on the luminescence and laser properties of the fibers.