Erbium-activated silica xerogels: spectroscopic and optical properties

Silica-based sol-gel glasses activated by Er3+ ions are attractive material s for integrated optics (IO) devices such as frequency upconverters and opt ical amplifiers. Monolithic erbium-activated silica xerogels with erbium co ntent ranging from 0 up to 40 000 ppm were prepared by the sol-gel techniqu e. Samples were densified by thermal treatment in air at 950 degreesC for 1 20 h. The densification degree and the relative content of hydroxyl groups were studied by Raman spectroscopy. Refractive indices were measured at 632 .8 and 543.5 nm by a prism coupling technique. Green to blue and violet upc onversion luminescence upon continuous-wave excitation at 514.5 nm was obse rved for all samples. Emission at 1.5 mum, characteristic of the I-4(13/2) --> I-4(15/2) transition of Er3+ ions, was observed at room temperature for all samples upon continuous-wave excitation at 980 nm. For the 5000 Er/Si ppm-doped xerogel, a photoluminescence was observed and a lifetime of 8 ms for the metastable I-4(13/2) level was measured. (C) 2001 Elsevier Science B.V. All rights reserved.