Design of metal electrodes with six important electrooptic materials

The coplanar electrode is analyzed by using conformal mapping and image methods where the electrode thickness is very thin. Three electrode configurations (symmetric, asymmetric and negative symmetric) are analyzed with six electrooptic materials (ADP, KDP, LiNbO₃, LiTaO₃, KNbO₃ and BaTiO₃) to find the characteristic impedance, Z, and the electric field components, E_x and E_y. The dimensions of the electrodes and the thickness of electrooptic material are designed to realize a matching impedance of 50 ohms. The impedance decreases when the relative permittivity, ε_r of the electrooptic material increases but it increases with a buffer layer. There is one or more compatible substrate materials for each electrooptic material. The effect of the shielding electrodes is discussed. The above methods give good accuracy as compared to the finite element method (FEM). The numerical results can be used as guide design curves.