This report presents a discussion of the engineering issues and results of high power 2μm Tm3+-doped fibre lasers pumped at 790nm. To date we have achieved up to 85W from such devices with 54% slope efficiency relative to launched pump. More recently, through using Tm3+ concentrations of approximately 4(wt.)% to enhance the cross-relaxation process (3H4,3H6->3F4,3F4) we have demonstrated slope efficiencies of up to 67% relative to launched power. This represented ~170% quantum slope efficiency for the 790nm pumped 2μm laser.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.