Optimization of the optical properties of a deeply etched semiconductor electrooptic modulator

A rigorous numerical study of a deeply etched semiconductor electrooptic modulator is presented. A Laplace equation solver followed by a full-vectorial modal solution technique for general anisotropic optical waveguides, all based on the versatile finite-element method, is used to find the potential distribution, the modulating electric fields, the changes in the permittivity tensor associated with the electrooptic effect, and the different modes of propagation. In particular, the optimization of the optical properties of the modulator structure such as the half-wave voltage length product V_πL and the optical losses due to the imperfectly conducting electrodes has been carefully carried out and results reported. In addition, the effect of the waveguide parameters on the microwave properties such as the microwave index n_m and characteristic impedance Z_c is explained.