2-PHOTON EXCITATION AND BLEACHING OF THE 400 NM LUMINESCENCE BAND IN GERMANIUM-DOPED-SILICA OPTICAL FIBERS

The 400 nm luminescence band of germanium-doped-silica optical fibres was excited via two-photon absorption of an argon ion laser beam. It w as observed that the photoluminescence decreased by as much as 25% dur ing the exposure of the fibres to several hundred milliwatts of optica l power for a few hours. Surprisingly, the amount of bleaching is not a given proportion of the initial intensity of the luminescence band. These luminescence measurements are qualitatively related to the photo sensitivity of the optical fibres. The saturation of two-photon absorp tion at relatively low power is also observed.