Abstract

The high-frequency performance of traveling wave optical modulators is ultimately limited by the difference in the propagation velocities between the RF and optical signals.¹ This velocity mismatch leads to a phase asynchronization at higher frequencies that allows the latter part of the traveling wave structure to cancel the modulation produced by the forward part. One approach that overcomes this limitation, and that leads to efficient bandpass operation at millimeter wave frequencies, is to use a periodic intermittent interaction electrode² (Fig. 1). The periodic electrode "resets" tire phase relationship between the RF and optical signal at predetermined points along the traveling wave structure, so that each section of the traveling-wave structure makes a positive contribution to the overall modulation. This paper presents experimental results for an X-cut LiNbO₃ Mach-Zehnder interferometric modulator with a periodic electrode structure designed for optimum operation at 35 GHz.

© 1991 Optical Society of America