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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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 · National Research Council Canada

    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).