Table of Contents
Physics Research International
Volume 2013, Article ID 379041, 14 pages
http://dx.doi.org/10.1155/2013/379041
Review Article

A Minireview of the Natures of Radiation-Induced Point Defects in Pure and Doped Silica Glasses and Their Visible/Near-IR Absorption Bands, with Emphasis on Self-Trapped Holes and How They Can Be Controlled

Impact Glass Research International, San Carlos, SON, Mexico

Received 9 May 2012; Accepted 19 October 2012

Academic Editor: Robert McLeod

Copyright © 2013 David L. Griscom. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The natures of most radiation-induced point defects in amorphous silicon dioxide (a-SiO2) are well known on the basis of 56 years of electron spin resonance (ESR) and optical studies of pure and doped silica glass in bulk, thin-film, and fiber-optic forms. Many of the radiation-induced defects intrinsic to pure and B-, Al-, Ge-, and P-doped silicas are at least briefly described here and references are provided to allow the reader to learn still more about these, as well as some of those defects not mentioned. The metastable self-trapped holes (STHs), intrinsic to both doped and undoped silicas, are argued here to be responsible for most transient red/near-IR optical absorption bands induced in low-OH silica-based optical fibers by ionizing radiations at ambient temperatures. However, accelerated testing of a-SiO2-based optical devices slated for space applications must take into account the highly supralinear dependence on ionizing-dose-rate of the initial STH creation rate, which if not recognized would lead to false negatives. Fortunately, however, it is possible to permanently reduce the numbers of environmentally or operationally created STHs by long-term preirradiation at relatively low dose rates. Finally, emphasis is placed on the importance and utility of rigorously derived fractal-kinetic formalisms that facilitate reliable extrapolation of radiation-induced optical attenuations in silica-based photonics recorded as functions of dose rate backward into time domains unreachable in practical laboratory times and forward into dose-rate regimes for which there are no present-day laboratory sources.