Design of Traveling-Wave Electrode for Silicon Mach-Zehnder Electro-Optic Modulator

In this paper, a new differential-drive traveling-wave electrode with wide bandwidth used to drive silicon-based Mach-Zehnder modulator (MZM) is proposed. The electrode is achieved by loading the partly removed Si substrate under the coplanar waveguide (CPW). By using the modified substrate, the transmission loss of the microwave signal can be effectively reduced compared with the signal with overlapping substrate. The bandwidth $\left(\left|S_{21}\right| \leqslant -3 \mathrm{dB}\right)$ of the presented electrode is well improved, which can reach at 28 GHz from 0.1 to 28.1 GHz. The electrode owns the merits of wide bandwidth, high phase shifting efficiency, and low cost. Thus, the proposed electrode has great values and broad prospects in the high-rate optical communication applications.