Abstract

High gain amplification has been demonstrated at 1310 nm with a Pr-doped fluorozirconate fiber [1], but with a much lower pump efficiency than a comparable Er-doped silica amplifier at 1550 nm. This low pump efficiency is attributable to the low quantum efficiency of the ^lG₄->³H₅ transition of Pr³⁺ [2], which follows from the preponderance of multiphonon mediated decay from the ¹G₄ to the nearby ³F₄ level. The probability of multiphonon decay between two energy levels is inversely related to the number of phonons required to bridge the energy gap. Therefore, the lowering of this probability and an improvement in the quantum efficiency would be expected through the use of a host material with lower phonon energies. In addition, an improvement in the quantum efficiency also would be expected in those materials with larger ^lG₄->³H₅ radiative rates. Over the last year a number of potentially more efficient host glasses have been reported [3,4,5,7]. Here we consider two of these, the mixed-halides [4] and the lanthanum gallium sulfide (LaGaS) [3], in detail.

© 1993 Optical Society of America