Chapter 17 - Rare Earth Doped Lasers and Optical Amplifiers

Abstract

Rare earth ions are used widely in optical gain media. The most important applications are in (i) optical amplifiers for telecommunication networks, especially erbium-doped glass fiber amplifiers and (ii) solid state lasers. Erbium-doped fiber amplifiers are by far the most important amplifiers in the world's optical fiber communications system. They are used to amplify weakened signals about every 80km along a fiber transmission line. They are compact, rugged, and reliable. They are able to handle up to 160 channels, e.g., 160 simultaneous telephone conversations, per fiber. Rare earth ions are also used in lasers, specifically in the near infrared region. Neodymium lasers emit at around 1μm, erbium 1.5-2.9μm, thulium and holmium ~2μm. These lasers are mainly used in medical applications, especially for cataract removal (Nd3+) and laser surgery (Tm3+ and Er3+). However, they must be handled with extreme care to avoid damaging other tissues, especially the retina.