High power 2μm Tm3+-doped fibre lasers

Using Tm3+-doped double-clad silica fibre we have produced high power, high efficiency 2mum lasers. To date we have achieved a 59% slope efficiency relative to launched pump power using single end pumping and double passing the pump light. By pumping the fibre laser from both ends, we achieved up to 118W peak output power with 54% slope efficiency relative to launched power at 25% duty cycle. The quantum efficiency of this laser was 120% relative to launched pump power, which we attribute to a cross-relaxation process in Tm3+ (H-3(4),H-3(6)-->F-3(4),F-3(4)). We have also demonstrated fixed wavelength operation of the laser near 1.9mum by using fibre Bragg gratings.