Modal dimensionality and dephasing effects in slab waveguide electrooptic filters

The voltage-dependent transfer characteristics of multi-mode slab waveguide electrooptic filters have been reexamined analytically in considerable detail, with special attention to differential modal phase delays, modal dimensionality, and attenuation. An important determination was the minimum number of modes (i.e., minimum dimensionality) needed for a reliable representation of the model. We find that a dimensionality of 10 is essentially adequate for the device modeled, having thickness approximately 130 μm, operating near a 0.475-μm wavelength. In addition, we find that inclusion of an initial dead length, with the attendant depbasing of modes, is an important factor in achieving good agreement with experimental data. Suitable allowance for mode-dependent attenuation also aids in improving this match.