Design and optimization of integrated Mach-Zehnder modulators in X-cut lithium niobate thin film/si wafer

A Mach-Zehnder electro-optic modulator (MZM) was designed using AFM COMSOL software and fabricate using pulse laser deposition method in this work. A successful multilayer structure of (nanoSi/nano SiO/nano LiNbO3) was prepared at optimum condition that obtained previously using theoretical simulation. Two designs were simulated depended on millimeter scale and micrometer scale for device fabrication. The second design was depended for wave guide (WG) fabrication. The size of the utilized Si WG was in the range of 0.7-3 mu m, the results show that effective index tended to increase as the thickness and width of the Si WG increased, however, upon the addition of the LN layer, the effective index values decreased. The effective mode area increased in both MZM and MZM-LN devices alongside the Si WG width increment. In contrast, the effective mode area exhibited a reduction in the acquired values as the Si WG thickness increased. In the confinement variation, high confinement was noticed at a low Si WG width, while a high-order mode and low confinement were observed at a larger width. Refractive index of (Delta n >= 0.13) is required to achieve 100 GHz electrical modulation bandwidth, and a device length of 2 cm produced significant figure of merit (V pi center dot L) values in the range of 2.12-2.25.