Photosensitivity of composite erbium-doped phosphorosilicate optical fibres to 193-nm laser radiation

Results of studying photoinduced changes of a refractive index in the core of a composite erbium-doped phosphorosilicate optical fibre under pulsed UV irradiation at a wavelength of 193 nm and the annealing of these changes are presented and analysed. It is shown that the preliminary saturation of a composite optical fibre by molecular hydrogen substantially increases the photosensitivity. Analysis of thermal anneal kinetics revealed fundamental differences in the photosensitivity mechanisms between the optical fibres saturated with hydrogen and not subjected to hydrogen treatment. Initial and photoinduced absorption spectra of the phosphorosilicate glass are investigated. It is found that in the UV range, the induced absorption is mainly determined by a contribution from the intense absorption band of photoinduced phosphorus electron centres PO₂ with a maximum at 4.7 eV (λ = 260 nm).