Erbium-activated silica xerogels: spectroscopic and optical properties

Silica-based sol-gel glasses activated by Er3+ ions are attractive materials for integrated optics (IO) devices such as frequency upconverters and optical amplifiers. Monolithic erbium-activated silica xerogels with erbium content ranging from 0 up to 40 000 ppm were prepared by the sol-gel technique. Samples were densified by thermal treatment in air at 950 degreesC for 120 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 upconversion luminescence upon continuous-wave excitation at 514.5 nm was observed 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.