Interferometric waveguide modulator with polarization-independent operation

A Mach-Zehnder interferometric waveguide modulator is demonstrated which simultaneously modulates both TE and TM modes. Two sets of electrodes are utilized to provide approximate independent control of vertical and horizontal field components across the channel waveguides. In Z-X–cut LiNbO3 this is shown to provide two polarization-independent points of operation. With Ti-diffused waveguides operated at 0.633 μm we obtained 90–95% modulation with applied voltages of 1.3 and 44 V and also with −8 and −36 V. Electrode design and alignment are shown to be important factors in device operation.