Abstract
Two complex multilayer thin-film filters have been produced by reactive e-beam evaporation. The filter specifications were challenging with respect to design and manufacturing. The optimized design configurations of 29- and 44-layer structures for the two filters, based on TiO2 and SiO2 as high- and low-index materials, have been finalized. The total thickness for the 29-layer filter is 2.1 μm and for the 44-layer filter is 4.1 μm. The deposition conditions and optical parameters of the material used were optimized and the films were characterized using spectrophotometry, atomic force microscopy, x-ray diffraction, and scanning electron microscopy, prior to manufacturing of multilayer structures. The multilayer structures are also characterized using the same techniques. Extremely good spectral performance, matching design specifications, has been achieved for the two filters, with compact and smooth film surfaces and dense structure. Both filters have been subjected to optical and structural characterization, and the results are discussed. The multilayer filters also passed the standard tape test to show good adhesion of the films to the substrate. The performance of the prepared filter samples are comparable with similar characteristic samples prepared by more energetic techniques like sputtering.
