Properties and generation by irradiation of germanium point defects in Ge-doped silica

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Abstract

Ge doped amorphous silicon dioxide (Ge doped silica) has attracted the attention ofresearchers for more than 50 years. This material is used in many different technologicalfields from electronics, to telecommunication, to optics. In particular, it is widely used forthe production of optical fibers and linear and nonlinear optical devices.The optical fibers, which allow to transmit optical signals with high speed avoidinginterferences, are constituted by two regions with different refractive index values: core(inner part) and cladding (external part). To increase the refractive index of the core withrespect to that of cladding, Ge doping of silica is commonly used. Moreover, in the Gedoped fiber two main radiation effects are observed: the photosensitivity and the secondharmonic generation (SHG). The photosensitivity permits the induction of a spatialmodulation of the core refractive index (Fiber Bragg Grating (FBG)) and together withthe SHG, is useful to produce a great number of devices.The Ge related point defects are considered relevant for the photosensitivity and theSHG, but at the same time they are also causes of the degradation of the fibertransmission properties. For these reasons and for new application fields as the silicabasedsystems for nuclear environments, the defect structures, their properties, theirassociated optical activities, their generation and conversion processes have been widelystudied and represent crucial arguments for ongoing research. These arguments havedouble valence, as they can be considered from a physical point of view and from thetechnological one.In this chapter, we will consider many aspects of the generation processes of thedefects by irradiation, with particular attention to paramagnetic defects Ge(1), Ge(2) andE’Ge, and to oxygen deficient optically active defects as the Germanium Lone PairCenter (GLPC). Some connections between material properties and defects generationwill be investigated too.We will start providing a background on the literature dealing with the Ge dopedglasses, their applications, the effects of the irradiation and the principal types of defects.After that, the principal properties of the investigated materials will be briefly described.The main part of the chapter will be dedicated to the presentation and the discussion ofexperimental data. These data concern the γ and the β radiation effects on varioussamples and the studies on some properties of the induced defects. Finally, we willpresent the main conclusions that can be derived by the data.
Original languageEnglish
Title of host publicationGermanium: Properties, Production and Applications
Number of pages75
Publication statusPublished - 2012

Publication series

NameChemical Engineering Methods and Technology

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)

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    Gelardi, F. M., Agnello, S., & Alessi, A. (2012). Properties and generation by irradiation of germanium point defects in Ge-doped silica. In Germanium: Properties, Production and Applications (Chemical Engineering Methods and Technology).