High-stability coatings for space optics: application to Silex program

Patrice Davi

doi:10.1117/12.188108

30 September 1994 High-stability coatings for space optics: application to Silex program

Patrice Davi

Proceedings Volume 2210, Space Optics 1994: Space Instrumentation and Spacecraft Optics; (1994) https://doi.org/10.1117/12.188108
Event: Space Optics '94, 1994, Garmisch, Germany

Abstract

In space optics, optical components are required more and more insensitive to extremely severe environmental conditions, with guaranted time of life and, concerning coatings, very severe spectral specifications. For most applications, coatings made with oxyde layers are not anymore convenient, because of their low compactness. Absorption and desorption of water in atmospheric or vacuum conditions induce stress in the stack which can involve incertainty in the stability in life. Indexes of materials are higher in atmospheric pressure than in vacuum, which makes shift the spectral curve. High and low index material which are quarter wave during evaporation in vacuum are not anymore quarterwave after beeing put in atmospheric conditions, which can completely affect the shape of the spectral curve. This phenomenon is particularely sensitive for bandpass interference filters which cannot be manufactured by classic thermal evaporation of oxyde materials. Less hard coatings can be used if protected by bonding but these kinds of components are sensitive to climatic conditions, involving changes in wavefront. Moreover, the resistivity of the cement to irradiations is not fully convenient. So it was necessary to develop new kinds of hard coatings with very high compactness, deposited on external faces of single substrates. In the contex of spatial programs, the coating Laboratory of MATRA has developped such components. Based on materials which are not oxydes, these coatings are perfectly compact so that their spectral curve is completely insensitive to air vacuum transition. Moreover, their hardness make them cleanable and resistive to adhesion and abrasion test. These qualities has been obtained by the choice of materials and the optimisation of their conditions of evaporation, the procedure including only classic thermal evaporation, without any kind of assisted ion gun. Many kinds of coatings can be made by these procedures which provide components of very high stability in terms of time of life and during all environmental conditions

Citation Download Citation

Patrice Davi "High-stability coatings for space optics: application to Silex program", Proc. SPIE 2210, Space Optics 1994: Space Instrumentation and Spacecraft Optics, (30 September 1994); https://doi.org/10.1117/12.188108

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