AVS 52nd International Symposium
    Thin Films Thursday Sessions
       Session TF-ThM

Paper TF-ThM1
Refractive Index Control of Sputtered Multicomponent Bismuthate Glass Films for Bi-EDWA

Thursday, November 3, 2005, 8:20 am, Room 306

Session: Optical Thin Films
Presenter: J. Kageyama, Asahi Glass Co., Ltd., Japan
Authors: J. Kageyama, Asahi Glass Co., Ltd., Japan
Y. Kondo, Asahi Glass Co., Ltd., Japan
M. Ono, Asahi Glass Co., Ltd., Japan
N. Sugimoto, Asahi Glass Co., Ltd., Japan
Correspondent: Click to Email
Multicomponent bismuthate glass films were deposited from a glass target by radio frequency planar magnetron sputtering for fabricating bismuthate erbium doped waveguide amplifier (Bi-EDWA).@footnote 1, 2@ It is essential to control the refractive index of the film, because it affects the beam propagation in optical waveguide structure. The appropriate refractive index difference between the core and the cladding of Bi-EDWA is about 0.03. Thus it is desired that the batch-to-batch reproducibility of refractive index is less than 0.001. The refractive index of the film is mostly stable during the beginning of target life, however it decreases as the total sputtering time increases. In this work, it was revealed that the main reason why the refractive index varies is not the change of cationic composition in the film, but the increase of oxygen concentration in the film as the deposition rate decreases. It was also found that the decrease of deposition rate is caused by the decrease of sputtering rate. Additionally it was considered that the decrease of sputtering rate is linked with the decrease of self bias voltage at the target as the target becomes thinner. We also examined the effect of new magnetic circuit having an improved magnetic alignment and a lower magnetic flux density to make the above-mentioned film properties stable. As a result, we succeeded in obtaining good reproducibilities of refractive index and deposition rate dramatically. It is expected that this method is widely applied in sputtering of insulating films and effective for suppressing the decrease of deposition rates and the variation of film properties. @FootnoteText@ @footnote 1@ Y. Kondo, M. Ono, J. Kageyama, M. Reyes, H. Hayashi, N. Sugimoto, Proc. OFC/NFOEC 2005, Anaheim, CA, USA, PDP2. @footnote 2@ Y. Kondo, M. Ono, J. Kageyama, H. Hayashi, M. Reyes, N. Sugimoto, Electron. Lett. 41, 317 (2005).