High-power diode-pumped ytterbium-doped fibre-laser
This thesis details the work I have done on double cladding ytterbium-doped fibre lasers. The two main subjects developed were the study of an efficient compact-launching system, and the operation of the double cladding compact fibre as a continuous-wave laser and a Q-switched laser.During this work, highly efficient side launching systems were developed. These allowed coupling of more than 70% of the pump light into the doped fibre and gave as good lasing efficiency as end-pumping system. The pump and the signal were also well separated in two different guides at the ends of the device. Efficient lasing at 976 nm (85% slope efficiency) was demonstrated too, by using small inner cladding area and double passed pump. Finally, pulse-energy as high as 7.7 mJ was achieved with a large core cladding pumped ytterbium doped Q-switched fibre laser.