Operation of Tm3+ fiber laser at λ = 2.3 μm coupled to a silica fiber Bragg grating

Abstract

A wavelength tunable all fibre laser which utilizes Tm3+-doped fluoride fibre as a gain mechanism emitting around a wavelength of λ = 2.3 μm is reported. Tm3+-doped fluoride fibre was coupled to a fibre Bragg grating inscribed in silica. This laser was evaluated by employing it as a wavelength tunable source in a methane gas optical sensor. A minimum gas detectivity of 100 ppm m limited by the ability to prepare low concentrations of gases was achieved. Emission wavelength control was implemented by thermally tuning the grating, although this method may prove to be too slow and cumbersome for practical use. A model describing the coupling between the silica fibre Bragg grating and the Tm3+-doped fibre was developed and integrated with a fibre laser model. This theoretical framework was used to examine the optimum silica and fluoride fibre parameters to achieve the maximum coupling between the fibres, with the aim of further reducing the fibre laser threshold.