Balanced bridge modulator switch using Ti-diffused LiNbO3 strip waveguides

An experimental integrated optical version of the Mach-Zehnder interferometer switch, analogous to the microwave balanced bridge, is reported. The bridge is formed by 3-μm-wide Ti-diffused strip waveguides in LiNbO3 and the switch utilizes electro-optical tuning to achieve 3-dB operation of the directional couplers. The switching voltage required to switch between the states, corresponding to a π phase shift in one arm, equals 14.8 V. The cross talk between channels that corresponds to the extinction ratio when operated as an on-off modulator is −21.6 dB.