A study on the effects of refractive index and geometrical variations in femtosecond laser-written lithium niobate waveguides

This study employs the finite element method (FEM) to simulate refractive index changes in lithium niobate induced by femtosecond laser writing and analyses their effects on waveguide modes and propagation loss. By adjusting refractive index contrast and geometric parameters, we investigate their impact on waveguide performance. A ridge waveguide structure is further designed to examine propagation loss under different configurations. Results demonstrate that optimized laser writing conditions and structural design can significantly reduce loss and improve optical performance. The feasibility of FEM simulation for waveguide design is verified, offering theoretical support for integrated photonic applications.