Integrated Dual-Mode 3-dB Power Splitter Based on Multimode Interference Coupler

We design and experimentally demonstrate a dual-mode 3 dB power splitter based on the self-imaging effect in a taper-assisted multimode interference (MMI) coupler. The quality reduction of the two mirrored half-power images of the input field due to accumulated high-order eigenmodes phase error will degrade the performance of dual-mode power splitter. We propose an eigenmode-selective-excitation method to suppress the excitation of high-order eigenmodes in the MMI. By optimizing the geometric parameters and injection position of the input taper waveguide, we realize power ratios of 95.9 % and 94.2 % for the lowest three and five eigenmodes when input TE 0 and TE 1 modes, respectively. The fabricated device occupies a footprint of 5\,\,\mu \text{m}\,\,\times 86.5\,\,\mu \text{m} with 5.2~\mu \text{m} assisted tapers. The measured excess losses and crosstalks for both modes are less than 0.76 dB and-20.5 dB, on average, over the observable 60 nm bandwidth, respectively, which are consistent with the numerical simulations.