Origin of crystallization-induced refractive index changes in photo-thermo-refractive glass

    Authors

    J. Lumeau; L. Glebova; V. Golubkov; E. D. Zanotto;L. B. Glebov

    Comments

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    Abbreviated Journal Title

    Opt. Mater.

    Keywords

    Crystallization; Refractive index change; Photosensitivity; Optical; glass; Stress; PHOTOTHERMOREFRACTIVE GLASS; BRAGG GRATINGS; STRESSES; Materials Science, Multidisciplinary; Optics

    Abstract

    Photo-thermo-refractive (PTR) glass is a multi-component silicate that undergoes localized refractive index decrease after UV-exposure and thermal treatment for partial crystallization. Based on this refractive index change, high efficiency volume Bragg gratings have been developed in PTR glass and have been successfully used for laser beam control. However, despite the fact that this type of glass has been widely studied and used over the last 20 years, the origin of the refractive index change upon crystallization is poorly understood. In this paper, we introduce three possible mechanisms (the precipitation of nano-sized NaF crystals and the associated local chemical changes of the glass matrix, the volumetric changes due to relaxation, and the local residual stresses) for the refractive index decrement in PTR glass and estimate the partial refractive index change due to each mechanism. Refractive index measurements are compared with high temperature XRD experiments and a general approach for the simulation of the refractive index change in PTR glass is proposed. We show that among the studied variables the residual stresses surrounding the crystals are the main responsible for the local refractive index decrement in this glass. (C) 2009 Elsevier B.V. All rights reserved.

    Journal Title

    Optical Materials

    Volume

    32

    Issue/Number

    1

    Publication Date

    1-1-2009

    Document Type

    Article

    Language

    English

    First Page

    139

    Last Page

    146

    WOS Identifier

    WOS:000271888500026

    ISSN

    0925-3467

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