High power double-clad Tm-doped fibre laser with >12 W single-mode output at 2 /spl mu/m

Summary form only given.High power sources operating in the 2 /spl mu/m region have applications in medicine and LIDAR, and also provide an ideal starting wavelength for nonlinear frequency conversion to the mid-infrared spectral region. For many of these applications the need for high power and high efficiency are also accompanied by the requirement for good beam quality. This combination of operating characteristics is often difficult to achieve in bulk solid-state lasers due to strong thermal effects which degrade beam quality and reduce efficiency. Cladding-pumped fibre lasers offer an alternative route to power-scaling with the attraction that heat generated due to the laser pumping cycle can be dissipated over a long length of fibre, minimising the risk of thermally induced damage. In addition, the output beam quality is determined by the waveguiding properties of the doped core, which can easily be tailored to produce a single-mode output. In this paper we report a Tm-doped silica fibre laser with a single-mode power of 12.2 W for 38.3 W of launched diode pump power. To the best of our knowledge, this is the highest power in the 2 /spl mu/m spectral region so far reported for a fibre laser.