Photoinduced absorption and refractive-index induction in phosphosilicate fibres by radiation at 193 nm

The photoinduced room-temperature-stable increase in the refractive index by ~5 × 10^-4 at a wavelength of 1.55 μm was observed in phosphosilicate fibres without their preliminary loading with molecular hydrogen. It is shown that irradiation of preliminary hydrogen-loaded fibres by an ArF laser at 193 nm enhances the efficiency of refractive-index induction by an order of magnitude. The induced-absorption spectra of preforms with a phosphosilicate glass core and optical fibres fabricated from them are studied in a broad spectral range from 150 to 5000 nm. The intense induced-absorption band (~800 cm^-1) at 180 nm is found, which strongly affects the formation of the induced refractive index. The quantum-chemical model of a defect related to this band is proposed.