Design and Simulation of Single Mode Rib Waveguide Based on Thin Film Lithium Niobate on Insulator

The demand for high capacity and superfast optical communication interconnects, has led to advancement in optical waveguide technology. Thin film Lithium niobate-on-insulator (TFLNOI) has recently emerged as a promising optical material platform for advanced photonic integrated circuits (PICs) owing to the excellent electro-optic properties of lithium niobate (LN). Apart from the variation of a material index, the optimization of the width and height of the waveguide core is observed to improve the confinement of electromagnetic waves across the rib waveguide. In this paper, a single mode (SM), z-cut rib waveguide device was designed and simulated using VPI photonics simulation software. With the aim of operating within the single-mode conditions (SMCs), the effect of the width (w) on the mode distribution and the effective refractive indices of LNOI rib waveguide at a fundamental wavelength of 1550 nm were demonstrated. The width of the rib was varied from 700 nm to 1200 nm with the height of the slab (H) fixed at H=700 nm. The results indicated that the effective refractive index increases gradually with the increase in width from about 700 to 1100 nm, and the mode distribution shows increased electromagnetic field confinement as observed in the Gaussian fields.