Grating Coupler Design for Vertical Light Coupling in Silicon Thin Films on Lithium Niobate

In this paper we provide a design for a vertical grating coupler for a silicon thin film on lithium niobate. The parameters-such as the cladding layer thickness of lithium niobate, fiber position, fiber angle, grating period, and duty cycle are analyzed and optimized to reduce the mode mismatch loss and the internal reflections. The alignment tolerances, for the grating coupler parameters, are also simulated and evaluated. We determine that our simulated grating coupler exhibits high efficiency, enhanced light coupling, and high alignment tolerance.