Feasibility of constructing a UV fibre laser based on a nitrogen-doped silica optical fibre

Nonlinear frequency conversion of neodymium laser (λ = 1.06 μm) radiation was observed when this radiation was injected into the core of a single-mode optical fibre made of nitrogen-doped silica. This resulted in generation of visible violet and near-ultraviolet radiation (355 — 430 nm). The conversion efficiency was up to 2 × 10^–4. The observed UV radiation was the result of the following processes: generation of the third harmonic of the fundamental pump frequency, stimulated Raman scattering of the third harmonic, and generation of the third harmonics of the Raman-scattered components of the pump radiation. Lasing was also observed in the 380 —430  nm wavelength range at colour centres associated with the presence of nitrogen in the silica core.