Short-pulse, high-peak-power Q-switched Tm–silica fibre laser at 1.9 μμm

High-performance Tm–silica fibre lasers operating at 1.9 μμm when pumped at 1319 or 1064 nm have been Q-switched using a rotating mirror mounted at an asymmetric angle. Pumping by 1319 nm gives better performance compared with 1064 nm pumping due to greater excited state absorption (ESA) at 1064 nm. A short Q-switched pulse duration of 25 ns and a peak pulse power of about 2.7 kW has been obtained from a 1.8 m fibre for 3.5 W launched pump power at 1.3 μμm. The Q-switch performance has been studied for variation of fibre length and shown that the optimum length under these pumping conditions is around 2 m.