AVS 47th International Symposium
    Thin Films Thursday Sessions
       Session TF-ThM

Paper TF-ThM10
Inhomogeneous Optical Coatings Deposited by Plasma

Thursday, October 5, 2000, 11:20 am, Room 203

Session: Optical Films
Presenter: D. Poitras, National Research Council, Canada
Authors: D. Poitras, National Research Council, Canada
L. Martinu, Ecole Polytechnique, Canada
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Inhomogeneous optical coatings with a refractive index continuously varying with thickness appear to offer several attractive features from both fundamental and application points of view: (1) Understanding how accidentally-generated inhomogeneities can affect the optical performance of coatings can help to optimize the performance of optical filters; (2) purposely introduced and controlled optical inhomogeneities can be used to fabricate high performance inhomogeneous optical systems such as rugate filters; and (3) coatings with graded interfaces generally exhibit higher mechanical strength, better adhesion and good long term stability. In the present work, we studied these different aspects of inhomogeneous coatings produced by plasma enhanced chemical vapor deposition (PECVD). We used admittance diagrams (i) to interpret recent results concerning the effect of transition layers on the reflectance spectra of homogeneous single films, and (ii) to derive an alternative explanation of specific properties of rugate filters. In addition, we describe a simple way for introducing the refractive index dispersion while designing rugate filters. The latter approach is documented by the performance analysis of complex refractive index profiles in a double band rugate filter and in a chirp mirror fabricated by PECVD.