Electro-optic cutoff modulator using a Ti-indiffused LiNbO(3) channel waveguide with asymmetric strip electrodes

A new type of cutoff light modulator, which consists of a single-mode channel waveguide and strip electrodes placed asymmetrically on either side of the guide, is proposed. When a voltage is applied to the electrodes, this device exhibits an asymmetric refractive-index profile along a direction parallel to the crystal surface through the electrooptic effect. This produces a strong condition for cutoff of the fundamental mode of the guide. An ultrahigh extinction ratio of greater than 56 dB has been achieved by using a Ti-indiffused Y-cut LiNbO(3) cutoff modulator with a 165-V drive at a wavelength of 0.6328 microm.