Interferometric polarization-independent modulator in LiTaO3

Polarization-independent Mach-Zehnder modulators that utilize the off-diagonal r₅₁ electrooptic coefficient are produced in LiTaO₃. The waveguides are formed by Zn vapor diffusion. Extinction values of 85% at 0.633-μm wavelength are demonstrated for both transverse electric and transverse magnetic polarization using a single control voltage and thermal tuning. The relatively large voltage-length product values (VL⩾15 V-cm) attained in these devices are attributed to a weak overlap between optical and electrical field profiles. Electrode alignment and dielectric loading are critical factors for the optimization of device operation