Abstract

Devices such as optical fibre gratings and waveguides whose fabrication is based on photoinduced effects of UV light are finding a growing number of applications in telecommunications, sensing and other areas.¹ Yet there remains some doubt as to the precise nature of the induced optical property changes being exploited, which leaves some question as to the permanence and reliability of such devices, especially when the responsible active material is not well known.^2,3 New research in this field should provide us with a still better understanding of a relationship between composition and structure,^4,5 and it should complement the already known information from existing techniques, such as EPR,⁶ NMR,⁷ photoluminescence⁸ and cathodoluminescence,⁹ X-ray diffraction¹⁰ and X-ray spectroscopy.¹¹ The Extended X-Ray Absorption Fine Structure (EXAFS) we propose here for such a purpose has been applied successfully for analysing glasses, in particular germanosilicate glasses.¹² However, what we are demonstrating is that EXAFS can be very appropriate also for studying devices such as optical fiber gratings and integrated optic waveguides. It should be emphasized that the rapid progress in both the detection and processing of EXAFS data made in recent years, together with the availability of appropriate synchrotron X-ray sources, have made this technique more applicable to routine tests than was possible previously.

© 1995 IEEE