Tunable and efficient diode pumped Tm3+-doped fluoride fibre laser for hydrocarbon gas sensing

The operation of an efficient CW thulium-doped fibre laser emitting at wavelength, lambda = 2.31 mu M is reported. The operation of the fibre laser is optimised with a view to producing a small and efficient laser source far optical absorption based gas sensing. A 2 mW output power combined with a high slope efficiency make this fibre laser a useful source for sensing spectroscopic based hydrocarbon gases which absorb at h = 2.3 mu n. A lower limit of detection of 1000 ppm metres for methane is routinely demonstrated using an unoptimised laser system. The tunability of the fibre laser has also been investigated in order to target specific hydrocarbon absorption features.