Rare-earth-doped sol-gel waveguides: a review

Sol-gel-based photonic components' technology is gaining an increasing interest. This is due in part to the overall properties of the sol-gel process, and in part to the specific characteristics which concern the inclusion into a glass matrix of nonlinear and/or active compounds, thus paving the way to the development of all-optical devices. Here a brief review is presented of the progress under way in the design and development of different sol-gel glass matrices where neodymium and erbium ions have been dispersed. So far, at our knowledge, a measurement of optical gain in this class of materials is still lacking; however, optical propagation and spectroscopic properties of the newly developed materials are quite satisfactory and perspectives of realizing lasers and amplifiers before too long are good.