Manufacture of complex optical multilayer filters using automated deposition system

It is now possible to design complex thin film multilayer coatings that can achieve almost any desired spectral performance. Moreover, these coatings can consist of tens or hundreds of layers each of which may have a differen t thickness. It is a challenge to accurately manufacture such complex coati ngs. An automated deposition system (ADS) has been developed which is able to fabricate complex optical coatings on a routine basis. This deposition s ystem uses a wideband optical monitor to accurately determine the deposited layer thickness and to re-optimize the remaining layer thicknesses, if req uired One advantage of this process is that no operators are required durin g the manufacture of a filter. For this technique to work, however, an ener getic deposition process such as sputtering is necessary in order to achiev e thin films with a bulk-like refractive index with little or no porosity o r inhomogeneity. As well, the optical constants of the thin film materials must be accurately known. A number of thin film filters have been manufactu red using this ADS. These include all-dielectric coatings as well as metal/ dielectric filters. in this paper, the ADS and the real-time process contro l algorithms will be described in more detail and several examples of manuf actured complex thin film filters will be described for different applicati ons. Crown copyright (C) 1998 Published by Elsevier Science Ltd. All rights reserved.