CW fluorescence and absorption spectra of erbium-doped fluoroaluminate glass

Abstract

Rare-earth (RE) doped fiber, erbium-doped fibers in particular, has already been successfully applied as optical amplifiers in optical telecommunication systems. Optically pumped laser systems based on RE doping also show promise in many diverse fields, among these are spectroscopy and medical surgery. Of particular interest to these applications is the operation of such laser systems in microchip configurations.
While the operation of optically pumped microchip lasers has already been demonstrated, they have mostly employed crystal host materials. There has been only one report of a microchip laser using a phosphate glass host. Glass host materials are more desirable since they are less expensive, can incorporate various dopant concentrations, and are readily manufactured as bulk elements or optical fibers. However, much higher RE concentrations are required in glass hosts to obtain sufficient absorption of the pump radiation in a thin sample. This is complicated by fluorescence quenching phenomena at high concentrations due to ion-ion interactions.
Heavy metal fluoride glass is ao attractive host material for compact laser configurations as its low phonon energies reduce non-radiative decay rates and increase radiative quantum efficiencies. High fluorescence intensities, with long lifetimes and minimal quenching effects have been reported for fluorozirconate glass with doping concentrations up to 18 mol%. However, it is hygroscopic and unsuitable for use in humid tropical climate. R Yanagita, et al., suggested that fluoroaluminates may be the most practical fluoride host for RE ions due to its superior chemical durability and mechanical properties.
The spectroscopy of RE-doped glass plays an important role in its utilization for optical device applications. All the important device characteristics of RE glass are fundamentally related to their spectroscopic properties. This paper reports the initial results of a spectroscopic study of erbium-doped fluoroaluminate glass. Included are the absorption and CW fluorescence spectra and the dependence of fluorescence intensity with the excitation power.