Optical gain in Er-doped SiO 2–TiO 2 waveguides fabricated by the sol–gel technique

Abstract

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 ≈1.1×10 20 Er 3+/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.