Optically active oxygen-deficiency-related centers in amorphous silicon dioxide

The spectroscopic properties, structure and interconversions of optically active oxygen-deficiency-related point defects in vitreous silica are reviewed. These defects, the E'-centers (oxygen vacancies with a trapped hole or 3-fold-coordinated silicons), different variants of diamagnetic "ODCs' (oxygen-deficiency centers), and their Ge-related analogs play a key role in the fiber-optic Bragg grating writing processes. The controversy surrounding the structural models for the Si- and Ge-related ODCs is discussed and the similarity between the bulk and surface point defects in silica is emphasized. The possible interconversion mechanisms between 2-fold-coordinated Si, neutral oxygen vacancies and E'-centers are discussed. The effects of glassy disorder have a profound effect on defect properties and interconversion processes in silica, (C) 1998 Elsevier Science B.V. All rights reserved.