CHARACTERIZATION AND SIMULATION OF PROTON EXCHANGED INTEGRATED OPTICAL MODULATORS WITH VARIOUS DIELECTRIC BUFFER LAYERS

Fast and accurate numerical techniques are developed for calculating the optical depth of modulation of integrated optical devices with various dielectric buffer layers. The matrix effective refractive-index (MERI) method is used in calculating the LiNbO3 proton exchange single-channel optical mode parameters. An approximate technique for calculating electrode electric field distributions as a function of various buffer layers is presented. Comparisons of computer simulations to experimental measurements performed on Mach-Zehnder modulators containing various buffer layers demonstrate that the numerical techniques are sufficiently accurate for computer-aided design (CAD) use. The error between calculated and measured V-pi is less than 3% for a modulator with a 60-nm SiO2 buffer layer and less than 1% with a 200-nm ITO electrode structure. In general, given the same electrode dimensions, the use of ITO electrodes results in a reduction of the drive voltage required as compared to electrodes on thin (< 100 nm) dielectric buffer layers.