Article

Design and Plasma Deposition of Dispersion-Corrected Multiband Rugate Filters

Department of Engineering Physics, Ecole Polytechnique de Montréal, Québec, Canada.
Applied Optics (Impact Factor: 1.78). 10/2002; 41(25):5249-55. DOI: 10.1364/AO.41.005249
Source: PubMed

ABSTRACT

Inverse Fourier transform method has been commonly used for designing complex inhomogeneous optical coatings. Since it assumes dispersion-free optical constants, introducing real optical materials induces shifts in the position of reflectance bands in multiband inhomogeneous minus (rugate) filters. We propose a simple method for considering optical dispersion in the synthesis of multiband rugate filter designs. Model filters designed with this method were fabricated on glass and polycarbonate substrates by plasma-enhanced chemical vapor deposition of silicon oxynitrides and SiO2/TiO2 mixtures with precisely controlled composition gradients.

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    • "One of the most common analytical design methods is based on the inverse Fourier transform [41] [42], which has several inherent limitations [43]. There is no generic analytical solution to date that will transform an arbitrarily complex reflectance (or transmittance) profile into a refractive index profile for real materials with dispersion and absorption [43] [44] [45]. Numerical optimisation techniques are therefore often employed to approach the optimum filter design iteratively. "
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    ABSTRACT: Ce travail est consacré à l'étude de la déposition de couches minces optiques et au contrôle de ce processus. Initialement, la tâche était de développer une technique de commande robuste pour ellipsométriques gradient d'indice de réfraction des couches. Au cours des travaux, il a évolué vers le domaine plus vaste de l'ECR PECVD de recherche et de contrôle optique multicouche ellipsométrie filtre. Malgré le fait que HDP-PECVD est utilisé couramment dans la fabrication microélectronique, de nombreuses questions sur cette technique sont encore sans réponse. Nous avons étudié les aspects de cette technique dans le but d'acquérir de nouvelles connaissances sur les processus physiques impliqués. Dans cette thèse, les parties suivantes de l'œuvre seront discutées, en vue de présenter une vision cohérente de l'objet: 1. Couches minces optiques, les plasmas et de la technologie de dépôt plasma. 2. ECR-PECVD caractéristiques et le développement. 3. Le système de dépôt MDECR Vénus et la caractérisation des plasmas de dépôt. 4. Déposition de filtres optiques à base de silicium oxynitrure alliages, et plusieurs techniques de caractérisation comme ellipsométrie spectroscopique. 5. ellipsométrie cinétique et le contrôle ellipsométrique de couches minces optiques. 6. Conclusion et recommandations pour les travaux futurs. Ces points représentent la structure de ce document. Ils seront détaillés dans les sections suivantes et développé dans les chapitres suivants.
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Questions & Answers about this publication

  • Daniel Poitras added an answer in Thin Films:
    Can any explain how to make a rugate broad band design in visible region?

    Thin film optics

    Daniel Poitras

    The bandwidth of the rugate, as for quarterwave stacks, is mostly set by the refractive indices contrast (nH/nL) in the design; the largest the contrast, the largest the reflection band. If you need sharp edges to the reflection band, the thickness required for doing that will be larger for rugate filters than for equivalent quarterwave stack, and even more if you use an apodization envelop with your rugate design.

    If you need to extend the band further, then you probably need to design a filter that will have 2 or more adjacent reflectance bands on the wavelength scale.  We have published a paper on that topic (see attachment), and I am sure that you could find other similar papers.  The resulting design profile will seem complex, but not necessarily complicated to make (some of these designs are not too sensitive to errors I believe).

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      [Show abstract] [Hide abstract]
      ABSTRACT: Inverse Fourier transform method has been commonly used for designing complex inhomogeneous optical coatings. Since it assumes dispersion-free optical constants, introducing real optical materials induces shifts in the position of reflectance bands in multiband inhomogeneous minus (rugate) filters. We propose a simple method for considering optical dispersion in the synthesis of multiband rugate filter designs. Model filters designed with this method were fabricated on glass and polycarbonate substrates by plasma-enhanced chemical vapor deposition of silicon oxynitrides and SiO2/TiO2 mixtures with precisely controlled composition gradients.
      Full-text · Article · Oct 2002 · Applied Optics