Narrow-band interference filters as phase accordant elements: comparison and theory

Classical narrow-band interference dielectric filters with all-dielectric reflectors have the quarter-wave stacks separated by a half-wave thickness (or multiple) spacer layer. These filters are essentially the Fabry-Perot filters and hence the theory developed for the latter applies in full. The paper presents the theory of narrow-band interference dielectric filters with non-conventional spacer layers. This spacer consists of the layers of two different materials. The optical features of these filters are compared with the features of Fabry-Perot filters. It is analyzed the influence of the errors of layer on spectral characteristics. Presented theory may be applied to any spectral ranges as well as to any thin film materials including absorbing and nonlinear materials.