Wafer-Scale Fabrication of Silicon Film on Lithium Niobate on Insulator (LNOI)

Hybrid integration of silicon photonics with lithium niobate (LN) devices provides a promising route to enable an excellent modulation performance in silicon photonic integrated circuits. To realize this purpose, a substrate containing a Si film on an LNOI substrate, called Si on the LNOI structure, was analyzed and fabricated. The mode propagation properties in the Si-on-LNOI structure were simulated in detail and a vertical adiabatic coupler (VAC) between the Si waveguide and LN waveguide was simulated to help in the determination of the dimension of this structure. A 4-inch wafer-scale Si on an LNOI hybrid structure was fabricated through the ion-cut process. This structure has a single-crystalline quality, high thickness uniformity, smooth surface, and sharp bonding interface, which are practical for realizing low loss and high coupling efficiency.