DEVELOPMENT OF LIGHT WAVEGUIDE OF FLUORIDE GLASS THIN FILMS BY COMBINED SOL-GEL AND FLUORINATION

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Recently much attention has been paid to rare-earth-containing fluoride glasses because of the high potentiality for active optical devices such as light delivery, fiber laser, optical frequency upconversion, optical amplification, photochemical hole burning memory and so on. A conventional preparation technique of fluoride glasses is batching, melting and quenching of the starting fluorides. Since several years ago, however, different preparation techniques have been attempted for various fluoride glasses to prepare glasses with forms suitable for active optical devices. It is anticipated that a multistep process incorporationg sol-gel synthesis and reactive atmosphere processing can be used to prepare momolithic fluoride glass films which can be used as optical waveguide. The present investigation succeeded in the preparation of rare-earth-containing fluorozirconate glass films by using metal alkoxides and an NF_3 gas as starting materials and a fluorination gas, respectively. Regretably, however, it was found that combined processes of sol-gel and fluorination is inadequate for preparing optical waveguide. Thus, an ECR microwave plasma CVD process was attempted as an alternative process. In this technique beta-diketonates of metals and an NF_3 gas were employed as starting materials and a fluorination gas, respectively. ZrF_4-BaF_2-LnF_3 glass films (Ln=Pr, Eu and Er) were successfully synthesized. Moreover the formation of optical waveguide was confirmed by observing the Er^<3+> upconversion luminescence of Er-doped ZrF_4-BaF_2 glass films.