SYNTHESIS AND RESEARCH OF THE OPTIMUM CONDITIONS FOR THE OPTICAL MONITORING OF NON-QUARTER-WAVE MULTILAYERS

Many optical filtering problems require the use of assemblies of layer s with thicknesses that bear no obvious relationship to each other. He re we present the results obtained for a number of examples in which o ptical monitoring is performed with a change of control wavelengths fo r each layer of the stack. For this, it is necessary to determine for each layer the different wavelengths that provide an extremum of trans mittance when the required thickness is achieved. We show that this le ads, in some cases, to making the benefit of error compensation analog ous to the well-known method used in the production of quarter-wave st acks. Because ion-assisted deposition and ion-plating techniques are s uitable from the point of view of refractive-index reproducibility, op tical 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 unifor mity are critical for high-performance coatings. Here we show how unif ormity can be determined for each material involved.