Optimized design of 1x4 optical splitter based on annealed proton exchanged waveguides in LiNbO3 crystal

A 1x4 optical splitter based on annealed proton exchanged (APE) waveguides is designed and fabricated. The beam propagation method and refractive index profile of APE waveguide are analyzed numerically. The symmetry of the optical splitter is reformed and optimized by adding straight waveguide in the cascaded Y-branch structure. The relationship between the length of the straight waveguide and the beam-slipper coefficient is obtained. The function of the 1x4 optical splitter is simulated by the commercial software BeamProp (RSoft). And the result indicates that the output uniformity of the optical splitter is improved when the length of the straight waveguide is 1935 mu m. Furthermore, the polarization-maintaining is gained in the 1x4 optical splitter since only the TE mode can propagate in the APE waveguide in X-cut LiNbO3 crystal. Finally, the optical splitter is fabricated and tested experimentally and the results show good agreement with the simulation.