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The use of molecular beam technology (MBD) under ultra high vacuum conditions (UHV) has proved to be a highly controllable process capable of producing dense films which are free of porosity, low in impurities and having bulk like optical properties. These distinctions are requisite for coatings which require a high laser damage threshold, low scatter and stable spectral characteristics. The application also lends itself to the formation of novel distributed Bragg reflectors (DBR) and rugate structures which require a highly controllable deposition process to form the many, often very thin, layers involved. In order to further the research in this field and produce advanced optical coatings for applications requiring stringent specification beyond the capability of conventional technology, a VG Semicon V90H MBE system has been installed at OCLI, Scotland, purchased and operated under a joint venture between OCLI Ltd and Heriot Watt University. This facility can provide a thickness uniformity of better than +/- 0.5% over a 4" substrate. This paper will review the current results from this unique deposition facility and describe the advances made in depositing complex multilayer coatings. |
