Intracavity absorption spectroscopy from 1.7 to 2 /spl mu/m with thulium-doped fibre laser

Summary form only given. We investigate a fibre laser based on a single mode silica fibre, doped with 1000 ppm Tm/sup 3+/. The fibre laser is excited by a laser diode (70 mW at 780 nm), and it includes an intracavity absorption cell filled with air or sample gases. The fibre laser has about 1 mW cw output power, and it call he tuned from 1.7 to 2 /spl mu/m by moving the aspheric lens, which couples the fibre to the output mirror through the absorption cell. For analysis of the laser emission spectrum we built a special rapid scan Fourier spectrometer with 0.015 cm/sup -1/ spectral resolution. Due to strong water vapour absorption near 1.85 /spl mu/m the Tm-doped fibre laser is especially suitable to make a water vapour detector of highest sensitivity.