1.91-1.99 μm Tm3+/Yb3+ co-doped tellurite fibre laser pumped using a 1088 nm Yb3+ fibre laser

We report the operation of a Tm³⁺/Yb³⁺ co-doped tellurite fibre laser operating in the range 1.91-1.99 μm when pumped with a 1088 nm Yb³⁺ doped silica fibre laser. Tellurite glass is a more chemically and environmentally stable glass than fluoride glass, making for improved long-term reliability of devices. Improved efficiency should be possible by pumping directly with a ˜980 nm laser source to take advantage of the high absorption in Yb³⁺ at this wavelength and also to minimise the required fibre length. This fibre laser exhibits strong blue fluorescence from the Tm³⁺:¹G₄ level due to 2-stage pump excited state absorption (ESA) which reduces the 2 μm efficiency by depopulating the Tm³⁺:³F₄ upper laser level.