Synthesis and research of the optimum conditions for the optical monitoring of non-quarter-wave multilayers.

ABSTRACT

Many optical filtering problems require the use of assemblies of layers with thicknesses that bear no obvious relationship to each other. Here we present the results obtained for a number of examples in which optical monitoring is performed with a change of control wavelengths for each layer of the stack. For this, it is necessary to determine for each layer the different wavelengths that provide an extremum of transmittance when the required thickness is achieved. We show that this leads, in some cases, to making the benefit of error compensation analogous to the well-known method used in the production of quarter-wave stacks. Because ion-assisted deposition and ion-plating techniques are suitable from the point of view of refractive-index reproducibility, optical monitoring can be used at a good level of performance. However, the production of high-quality optical thin films needs more than just the choice of a monitoring process. In particular, problems of uniformity are critical for high-performance coatings. Here we show how uniformity can be determined for each material involved.