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Abstract
Silicate glasses remain the most investigated systems for optical planar waveguides, since they offer a reasonable solubility for rare-earth ions, they are transparent in the near-infrared–visible region and they are compatible with integrated optics (IO) technology. In the last decade, various technologies have been employed for the fabrication of silica (SiO2)-based IO components and a broad variety of silicate glass systems have been investigated. Besides the SiO2–titania (TiO2) system, which has been widely studied, it has recently been shown that SiO2–hafnia (HfO2) could be a further viable system for 1.5 µm applications. This paper compares spectroscopic results, in particular infrared and Raman spectra, in order to assess the structural and optical properties of erbium-activated SiO2–TiO2 and SiO2–HfO2 planar waveguides, prepared by two different techniques: rf sputtering and the sol–gel method. Particular attention is devoted to the homogeneity of the material structures obtained in each case.
Acknowledgements
We would like to acknowledge the financial support of Fundação para a Ciência e a Tecnologia, through the Programa Operacional ‘Ciência, Tecnologia, Inovação’/Ciência e Tecnologia de Materiais/36109/99 project, of Fundo Social Europeu–Fundo Europeu de Desenudvimento Regional and Instituto de Cooperacão Científica e Tecnologica Internacional–Consiglio Nazionale delle Ricerche, through a collaborative grant on ‘Optical amplification’, of Consiglio Nazionale delle Ricerche–Centre Nationale de la Recherche Scientifique through a collaborative grant on ‘Improvement of the multi-target rf sputtering and sol–gel techniques for silica-based photonic component’ project, as well as that of Foreign Investment Review Board ‘Nanotecnologie, microtecnologie, sviluppo integrato di materiali’ and Ministero dell’Istruzione, dell’Università e della Ricerca (Programmi cofinanziati 2002) ‘Materiali nanostrutturati per l’ottica integrata’ Italian projects.