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Trends in optical thin film interference filters have created an increasing demand for the production of
high tolerance designs for a wide number of applications. Much has been achieved by conventional filter
designs but more novel structures such as distributed Bragg filters (DBR) and rugates are of increasing
interest. Such filters require a highly controlled deposition technology as many of the constituent layers are
only a few tens of angstroms thick.
At this previous conference (Hamburg 1988) the potential of molecular beam epitaxy (MBE) was discussed with
reference to the manufacture of such demanding structures. Although MBE equipment is usually associated with
the epitaxial growth of IIIV semiconductor material, the application has lead to the the availability of a
wide range of ultra high vacuum (UHV) equipment suitable for the deposition of optical thin films. To date,
considerable development has taken place with the commissioning of e Vacuum Generators V9OH production GaAs
machine, adapted for optical thin film fabrication.
This unit has a single 4" substrate capacity or multiples of smaller dimensions. Film thickness uniformity
of better than +1- 0.5% have been routinely achieved over the maximum substrate area using a single rotation.
Materials under current study include ZnSe, ZnS, BaF2 and PbF2. These offer candidate low and high index pairs
from the UV to the IR region of the spectra and have been shown to be compatible for incorporation in a single
chamber environment with minimal cross contamination.
In this paper, current results will be presented from this unique deposition facility with particular
emphasis on the gains made in depositing highly complex multilayer structures. An assessment will be given as
to the potential of molecular beam deposition (MBD) as a production technique.
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