Filter synthesis for coupled waveguides

The synthesis of realistic coupled waveguide filters is considered. The emphasis is on the synthesis of physical devices, rather than on the approximate coupled-mode representations. For this purpose, variational optimization is combined with the normal-mode analysis of interacting waveguides. Physical effects such as the change in coupling strength with waveguide or material dispersion are naturally taken into account. The beam propagation method (BPM) is used to verify the effectiveness of the designs and thus lends a measure of confidence of the applicability of the method to realistic devices.