High-efficiency CW operation of 890 nm pumped holmium fluoride fibre laser

Highly efficient CW operation has been observed from the holmium transition centred at 2.024 μm in a Tm:Ho co-doped single-mode fluoride fibre laser. When pumping holmium directly at 890 nm a minimum threshold of 8.2 mW launched pump power was observed for oscillation at 2.076 μm. A maximum slope efficiency of 30% was achieved for operation at 2.054 μm, which corresponds to a photon conversion efficiency of 69%