Abstract

The invention of erbium-doped fiber amplifiers (EDFAs) [1] evolutionized long-haul fiber-based optical communications. Erbium amplifiers have a number of unique properties highly suitable for optical communications, such as the broadband gain covering optical communication bands around 1550 nm, a long ms-lifetime of the parity forbidden intra-4-f shell transition that leads to slow gain dynamics and negligible inter-channel crosstalk, high temperature stability, and low noise figure. Rare-earth ion doping can equally provide a basis for compact erbium-doped waveguide amplifiers (EDWAs) [2]. Earlier efforts in the 1990s were made to implement EDWAs based on oxide glass waveguides, but these approaches were limited by large waveguide background losses, large device footprints and incompatibility with contemporary photonic integrated circuits. Recent demontrations of ED-WAs using Erbium-doped Al₂O₃, TeO₂ and erbium chloride silicate nanowire achieved output power of typically < 1 mW, far below the level demanded by many applications.

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