TCO-electrode BTO modulator toward 400G/800G interconnects: achieving 0.09  V·cm and bandwidth beyond 100  GHz

Silicon photonics is crucial for high-capacity interconnects in the post-Moore era. This paper examines the fundamental electro-optic (EO) conversion component within this technological framework and introduces a highly efficient Mach-Zehnder electro-optic modulator (EOM) based on a barium titanate (BTO) platform. This study innovatively employed a composite electrode structure of transparent conductive oxide (TCO) and gold. By reducing the electrode gap to enhance the RF electric field within the waveguide, while simultaneously capitalizing on the low optical absorption loss characteristic of the TCO material, the modulation efficiency is significantly improved. Simulation results indicate that the modulator can achieve a modulation efficiency of 0.09 V·cm, while the calculated electrode-induced optical absorption loss is only 0.001 dB/cm, with a bandwidth far exceeding 100 GHz. The insertion loss of the multimode interference (MMI) and edge couplers is 0.07 and 0.69 dB, respectively. Furthermore, to address the challenge of push-pull modulation for a-oriented BTO, we propose a novel dual-drive differential structure, to our knowledge, that not only effectively suppresses external electric field interference but also achieves efficient push-pull modulation.