The loading of Ge-doped SiO<sub>2</sub> with hydrogen at nearly room temperature and high pressure (200-700 bars) has been shown to increase by several orders the rate and the magnitude of the UV-induced refractive index change and its value. This pre-treatment is now widely used in industry for the purpose of Bragg grating-based components in telecommunication optical fibers. Its development is also currently in progress for integrated optics. Yet, in this case, the implementation of the technique proves to be more difficult due to rapid out-diffusion of the gas from a thin layer. Many groups have carried out experiments to understand the mechanisms of the enhancement in photosensitivity. In the course of this research, a photosensitization process has been discovered allowing a lock-in of photosensitivity. This points out a catalytic role of a hydrogen containing species. We have analyzed the results of various measurements (such as EPR, UV spectroscopy, and refractive index change) for suggesting a kinetics scheme.

© 2003 Optical Society of America

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