Strong refractive index changes induced in Ag+ ion exchanged Er doped phosphate glass using 248 nm excimer laser radiation
The photosensitivity of a commercial phosphate glass (Schott IOG-1), which is doped with Er3+ ions and has been ion exchanged with Ag+ ions, was examined using nanosecond 248 nm excimer laser radiation. Grating structures were inscribed in the untreated and ion exchanged Er doped IOG-1 glass by employing phase mask interference in contact mode. The dependence of ultraviolet induced refractive index changes upon the ion exchanged Ag+ concentration and the number of ultraviolet pulses was studied using diffraction efficiency measurements. Refractive index changes in untreated glasses are of the order of 10−5, whereas for silver ion exchanged samples they reach ∼2·0×10−3, for ultraviolet exposures of 30000 pulses of 400mJ/cm2 energy density. Measurements of the absorption spectra of exposed and unexposed samples were carried out in order to reveal absorption bands and illustrate photosensitivity mechanisms. Furthermore, energy dispersive spectrum microanalysis and scanning electron microscopy of the exposed ion exchanged glass samples reveal that ultraviolet radiation induces migration of the Ag+ ions towards the areas of high energy density.
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Document Type: Research Article
Publication date: April 1, 2005