Ultra-Compact Non-Travelling-Wave Silicon Carrier-Depletion Mach-Zehnder Modulators Towards High Channel Density Integration

Abstract

Silicon Mach-Zehnder modulators (MZMs) utilizing carrier depletion usually adopt traveling-wave (TW) electrodes for their long phase shifters, which have inherent challenges in miniaturization, limiting the integration density of monolithic transceivers. In this work, we experimentally demonstrate non-TW carrier-depletion MZMs that give better compromises between compact footprint, modulation depth, and high speed. They adopt densely meandered phase shifters and thus offer an ultra-compact lumped-element MZM for using carrier depletion. Up to 28.1 Gb/s NRZ eye diagrams and ∼26 GHz electro-optic bandwidth were experimentally achieved. The proposed lumped circuit model well explains the experimental data, indicating that impedance mismatching is the dominant factor in determining experimental bandwidth and a LC resonance contributes to the bandwidth improvement. Driving configurations with better impedance matching are proposed to further improve bandwidth. This novel MZM can enhance the integration density of modulators in wavelength-division multiplexing transceivers.