High-power Tm-doped fiber distributed-feedback laser at 1943 nm

We report on high-power operation of a fiber distributed-feedback (DFB) laser fabricated from Tm-doped photosensitive alumino-silicate fiber and in-band pumped by an $\mathrm{Er}∕\mathrm{Yb}$ fiber laser at $1565\mathrm{nm}$. The fiber DFB laser yielded up to $875\mathrm{mW}$ of single-ended output at $1943\mathrm{nm}$ on two orthogonally polarized modes for $3.5\mathrm{W}$ of absorbed pump power. Further scaling of the DFB laser output power was achieved with the aid of a simple Tm-doped fiber amplifier stage spliced directly to the DFB fiber without the need of an optical isolator. The maximum output power from the DFB laser and fiber amplifier was $>3\mathrm{W}$ for a combined absorbed pump power of $8.1\mathrm{W}$. The influence of thermal loading, owing to quantum defect heating in the Tm-doped core, on the output power and longitudinal mode behavior is discussed, and the prospects for further improvement in performance are considered.