Abstract
We report on recent progress in power scaling of cladding-pumped Er,Yb and Tm-doped silica fiber lasers in the ~1.5μm and ~2μm spectral regimes respectively, and also on some recent developments in fiber-bulk hybrid lasers based Er:YAG and Ho:YAG operating at ~1.6μm and ~2.1μm respectively. A cladding-pumped Tm-doped silica fiber laser pumped by a beam-shaped diode-stack at 790nm and with core composition optimized for efficient 'two-for-one' cross-relaxation yielded 66W of continuous-wave output at ~2μm for 117W of launched pump power. The corresponding slope efficiency with respect to launched pump power was 61%. An Er,Yb fibre laser, cladding-pumped by two spatially-multiplexed diode-stacks at 976nm and with core composition optimized for efficient energy-transfer from Yb<sup>3+</sup> to Er<sup>3+</sup>, yielded up to 188W of continuous-wave output at 1570nm with an average slope efficiency with respect to launched pump power of 41%. The prospects for a further increase in output power from Tm and Er,Yb fiber lasers are considered. Efficient operation of hybrid Er:YAG and Ho:YAG lasers, pumped in-band by Er,Yb and Tm doped fibre lasers operating at 1532nm and 1907nm respectively has been demonstrated. Both lasers, when operated in continuous-wave mode, had slope efficiencies with respect to incident pump power of ~80%. The Er:YAG laser produced ~60W of continuous-wave output at 1645.3nm for 82 W of incident pump power, and, in Q-switched mode, produced pulses of energy, ~5.5mJ and duration, ~81ns (FWHM) corresponding to a peak power of ~67kW at a repetition rate of 500Hz for an incident pump power limited by the onset damage to 16.8W. The prospects for further improvement in continuous-wave and Q-switched performance are discussed.
Published Version
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