Design and comparison of single-mode planar and ridge type electro-optic waveguide modulators

Electro-optic waveguide modulators utilizing phase retardation of two orthogonally polarized optical modes in LiNbO₃ and LiTaO₃ waveguides have been designed taking into consideration the optical field distribution in the waveguides and the electrical properties of the electrodes. The analysis has revealed that a driving-voltage to frequency-bandwidth ratio of 1 V/GHz is attainable at the wavelength of 1.05 m using presently available embedded and ridge waveguides. Improvement in waveguide fabrication techniques may reduce the ratio by at least a half. Thus, LiNbO₃ and LiTaO₃ waveguide modulators are considered to be promising candidates for practical application to single-mode optical-fibre transmission systems of higher than 1 Gbit/s.