Optimization design of optical waveguide in Mach-Zehnder electro-optical polymer modulator

In order to reduce transmission loss of the optical waveguide in Mach-Zehnder (M-Z) electro-optical (EO) polymer modulator, the basic iterative formula of semi-vector finite-difference beam propagation method (FD-BPM) is obtained from the scalar wave equation. The transition waveguide is combined with S-type bend branch waveguide for the M-Z EO modulator in the branch waveguide. The effects of structure parameters such as ridge width, length of the branch waveguide and interferometer spacing on the transmission loss are systematically studied by using the semi-vector FD-BPM method. The structure is optimized as an S-sine bend branch waveguide, with rib width w=7 μm, length of branch waveguide L=1200 μm and interferometer spacing G=22 μm. The results show that the optimized structure can reduce transmission loss to 0.083 dB, which have a certain reference value to the design of optical waveguide in M-Z polymer modulator.