In this work, different mixtures of SiO2 and Ta2O5 films were investigated for application in Rugate-filter-design. Not only optical properties were considered but also the mechanical and stoichiometric behavior especially with increasing thermal strain. It could be shown that different compositions of SiO2 und Ta2O5 show different behavior with increasing temperature. Furthermore, it was detected that the requirement of oxygen strongly correlates with the ratio of the two layer materials. Latter results in changes of the optical properties, which can entail the destruction of the optical performance of a Rugate filter. At the end of this article, some suggestions for Rugate design calculations are presented taking the results of this work into account. (C) 2008 Elsevier B.V. All rights reserved.