High power upconversion lasing at 810 nm, in Tm:ZBLANfibre

The Letter reports upconversion lasing at 810 nm in thulium doped fluorozirconate fibre pumped by an Nd:YAG laser at 1064 nm, with an output power greater than 1.2 W and slope efficiency of 37%. Tunability over the range 803–816 nm is demonstrated. This is the highest power and most efficient upconversion laser reported to date in any gain medium.