Photo-thermo-refractive glasses: crystallization mechanism for optical applications


Optics, Photorefractive materials


Due to their ability to undergo a refractive index change (.dn) induced by appropriate UV irradiation and thermal development, Photo-Thermo-Refractive (PTR) glass is a candidate material for use in optical applications such as hologram recording, optical data storage, or spectral filters.

Although this refractive index modulation (.dn) has been characterized in terms of its optical ramifications, glass scientists are working to understand more clearly the underlying mechanisms associated with the photo-induced crystallization process. Despite numerous difficulties such as the insulating nature of PTR glass, low concentration levels of photosensitive species, nanometer size of the resulting crystalline phase, and reactivity of these crystals to ion and electron beam radiation and temperature, characterization techniques have been successfully used, resulting in an improved understanding of the photo-induced crystallization mechanism.

Results of absorption spectroscopy, interferometry, thermal analysis, x-ray diffraction, transmission electron microscopy have allowed detailing a self-consistent mechanism to describe the multiple steps of this complex process.

The photo-induced crystallization process has been experimentally verified, step-by-step. Additionally, the evolution of the hetereogenous phase has been quantified.

Sodium fluoride precipitates that results from bulk crystallization were determined to be less than 0.25% of the total volume and were within the range of 8 to 14nm in size.

Experiments combining interferometry and x-ray diffraction analyses of glasses heterogeneously crystallized at 520°C for 1 hour led to a linear correlation between (.dn) decrement and UV exposure doses.

A kinetic study of the heterogeneous crystallization using thermal analysis revealed an exponential decay law linking the activation energy for heterogeneous crystallization as a function of the UV dose for given heat-treatments.


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Doctor of Philosophy (Ph.D.)


College of Engineering and Computer Science





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Doctoral Dissertation (Open Access)




Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic; Optics

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