Development of resonantly cladding-pumped holmium-doped fibre lasers

The resonant pumping of holmium fibre lasers provides a fibre laser platform capable of addressing a wide range of applications that benefit from operation at wavelengths beyond 2.1 μm. This architecture can provide laser devices that promise high efficiency sources in the 2.1 μm spectral region with excellent beam quality and power scalability. This paper presents our recent results of resonantly pumped pulsed and CW holmium fibre lasers. We have demonstrated the first efficient resonantly cladding-pumped holmium fibre laser source. We have investigated both single mode and large mode area fibres and achieved CW output powers of ~140 W with excellent beam quality. In addition to these CW lasers we have investigated core-pumped, pulsed holmium fibre lasers and demonstrated output energies of up to 16 μJ at a repetition rate of up to 600 kHz. These developments provide an opportunity to build a high average power, pulsed 2.1 μm laser for the purpose of power scaling future mid-infrared sources.