REFINED MODELING OF TRAVELING-WAVE TI-LINBO3 CHANNEL WAVE-GUIDE MODULATOR

A refined computation model for traveling-wave operation of external e lectro-optical phase modulators made of a single titanium in-diffused lithium niobate channel waveguide (Ti:LiNbO(3)WG) is described. The mo dulator circuit model outlined as two traveling-wave coupled microstri ps includes microwave losses and dispersion. In the optimization proce dure, we consider different circuit load conditions. The influence of a dielectric overlay covering the electrodes is examined The consolida ted techniques of conformal mapping, multiple image, and finite elemen t are used to investigate the microwave characteristics of the structu re, and the refractive effective index method is used in calculating t he characteristics of the diffused anisotropic optical channel. The pe rformances of Y-cut and Z-cut substrate configurations are compared. W e have verified that the Y-cut substrate modulator gives the best over all performance and that the overlay presence causes significant impro vements in the evaluated modulation efficiency and in the bandwidth. A model of the modulator that takes electrode thickness into account pe rmits one to obtain a wider bandwidth.