Optical gain in Er-doped SiO2-TiO2 waveguides fabricated by 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 approximate to 1.1 x 10(20) Er3+/cm(3), for possible application in integrated optic waveguide amplifiers. We have obtained high fluorescence lifetimes (> 8 ms), propagation loss values of 0.6-0.75 dB/cm at 1330 nm, and favourable fluorescence spectral shape. Relative gain levels up to 1 dB/cm 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. (C) 1999 Elsevier Science B.V. All rights reserved.