Erbium electron system

Stimulated by these ESR measurements, Weber et al. (1985-1987) and Brandt et al. (1994) published a series of detailed theoretical papers in which they proposed a new Jahn-Teller mechanism for Er " in mixed valence hosts. In this model the degenerate Er ground state interacts with excitations of the mixed-valent state, whereas the direct erbium-phonon interactions are as small as in conventional host crystals. The electron capture at the impurity site can be explained within this model by formation of a band-gap state in the coupled system. 

Light amplifiers are essential to all-optical systems (no electronic repeaters, no hght-to-electronic conversion) since they compensate for optical losses within the fibers and the associated connectors, couplers, and switches. They are achieved by doping the fiber core with fluorescent lasing ions such as erbium or neodymium, and pumping using laser diodes. 

---