MMI Waveguide Reflector Based on Lithium Niobate Thin Film

Based on the principle of multimode interference (MMI) imaging, an MMI waveguide reflector with high reflectivity, high bandwidth, and high process tolerance is designed using a lithium niobate thin film. The simulation results show that when the input light is transverse electric (TE) polarized, the maximum reflectivity of the designed MMI waveguide reflector is 96.5% at the working wavelength of 1.55 μm, and the bandwidth is 110 nm with more than 90% reflectivity. We also designed an experiment to measure its reflectivity. The experimental result of reflectivity is 85.24%. Compared with other proposed waveguide reflectors, it has the advantages of high reflectivity and large bandwidth. These results indicated that this optimized waveguide reflector design can be applied to integrated optical system based on lithium niobate thin film.