Abstract
The authors report the use of enhanced inter-ion cross-relaxation in Er:ZBLAN fibres of double clad geometries for the realisation of high-power (400 mW) diode-pumped 2.7 mu m lasers. The enhanced Er-Er cross-relaxation was enabled by the formation of clusters, around drawing-induced defects, even at moderate mean doping densities in such fibres. Further extension of this work should enable multi-Watt CW power level lasers at 2.7 mu m in the foreseeable future.