the sol–gel technique

The sol–gel technique is a highly flexible technique for fabrication of oxide glasses, and various researchers have previously reported fluorescence studies of Er-doped sol–gel films and monoliths. Here we report the fabrication of Er-doped strip-loaded sol–gel silicate waveguides, using a silica–titania–alumina host composition, and Er concentrations up to f1.1=10 Er rcm, for possible application in integrated optic waveguide amplifiers. We have obtained high Ž . fluorescence lifetimes )8 ms , propagation loss values of 0.6–0.75 dBrcm at 1330 nm, and favourable fluorescence spectral shape. Relative gain levels up to 1 dBrcm were obtained. These results indicate that about half the Er ions effectively contribute to gain, suggesting segregation of the remaining ions in crystallites or clusters of some kind. q 1999 Elsevier Science B.V. All rights reserved.