Sensitivity to RF Drive Power and the Temperature Stability of Mach-Zehnder Modulators

Waveguide electrooptic modulators usually require a DC bias voltage that is used to set an optical phase relation between waveguides to attain proper operation. In practice, the DC bias voltage consists of intrinsic and extrinsic components. The intrinsic component is that voltage necessary for an ideal device, which may be zero by design, while the extrinsic component is required to compensate for materials and fabrication imperfections and/or environmental influences. As the power supplies allowable for applications will place strict bounds on the bias voltage range, it is essential to prepare materials and formulate designs for maximum stability. In this work we concentrate on the temperature stability of traveling-wave Mach-Zehnder modulators, and, in particular, those fabricated in LiNbO3. We present results of experiments on the sensitivity of the bias point to RF drive power that emphasize the importance of structural symmetry in achieving environmentally stable devices.