Abstract

Over the past two years several upconversion-pumped visible laser systems based on lanthanide-doped fluorozirconate glass fibre have been reported[1-5], illustrating the great potential of this medium for efficient infrared to visible conversion. Confinement of pump radiation in a small core fiber lead to rapid multiple step pumping of high-lying metastable energy levels for fairly modest levels of pump power. Compared to silica fibers the low vibrational energies of the heavy metal fluoride glass matrix leads to a greatly reduced competition to optical pumping and emission processes from nonradiative decay. A further advantage relative to silica is the narrowness of the absorption and fluorescence bands giving higher peak cross-sections and less likelihood of unwanted excited state absorption(ESA). Fluoride fibre fabrication technology has now reached a point at which small core fibres (i.e. monomode in the visible) with scattering losses down to ~ 0.2dBm⁻¹ can be made, so that the remarkable properties of the fluoride glass host can be embodied in efficient compact devices.

© 1992 Optical Society of America