Analysis and Optimization of InP-InGaAsP MZI Modulators with Zinc Diffusion Effect

We investigate the effect of Zinc diffusion during MOCVD epitaxy on the modulation efficiency and optical insertion loss of InP-based Mach-Zehnder Interferometer (MZI) modulators, and propose an asymmetric active region design to overcome Zn diffusion effect. By quantitatively analyzing the electric-optical field distribution and free-carrier absorption loss, we demonstrate that positioning the MQW active region closer to the n-contact layer will improve the modulation efficiency of InP-based MZI modulators by 47% and reduce the absorption loss by 0.4 dB/cm under high Zn diffusion concentration, comparing with a symmetric active region design.