Absorption of erbium doped silicate glasses

Abstract

There is an interplay between developments in glass technology and advances in lasers and optical telecommunications systems. Many ions and host glasses were investigated and the features and merits of glasses as a host relative to crystals have been established. Optical parameters of doped glasses for different applications can be tailored by changing the chemical composition of the glass. The most common glasses studied are silicate, germanates, phosphates, and fluoride glasses doped with rare-earth ions.
Glasses are commonly made up of network formers, e.g. SiO₂, which form covalent bonded structure and network modifiers, e.g. Na⁺ forming ionic bonds with SiO^- groups which break up the covalent structure thus allowing more modest processing temperatures. The rare-earth ions (e.g. Er³⁺) added to the glass system as dopants, are usually trivalent and take the place of the network modifier. Presence of the nonbridging oxygen groups promote solubility and incorporation of the rare-earth ions into the glass. Thus, clustering which reduces radiative transitions is prevented.
Another important feature of the host glass environment is its effect on the rare-earth ions. This can be conveniently studied from absorption and fluorescence spectra of the doped glass. The widths of the various ion energy bands can be controlled to some degree by a suitable choice of host glass. The effect of the host glass is to perturb slightly the energy levels of the ions. The ligand field causes Stark splitting in the energy levels of the dopant ions which is similar to those of the free ions.
This paper reports on the initial results of the spectroscopic study of erbium:silicate glass systems jointly fabricated by the Laser Physics Laboratory and the Department of Science and Technology. These information are important in optimizing the parameters of the doped glass system for technological applications such as waveguides, optical fiber amplifiers, and microchip lasers.