An Integrated Few-Mode Power Splitter based on Multimode Interference

A 1×2 integrated four-mode power splitter based on multimode interference (MMI) is proposed and experimentally demonstrated for the first time. Three-dimensional (3D) simulation is used to optimize the core/cladding refractive index difference and the input waveguide position for the $\rm TE_{00}, TE_{01}, TE_{10}, and TE_{11}$ input waveguide modes. Minimum insertion loss (IL) and mode-dependent loss (MDL) of 0.1 dB and 0.2 dB are predicted, respectively. IL and MDL less than 1 dB can be maintained over a bandwidth of approximately 50 nm and 25 nm, respectively. The device was fabricated on $\rm SiO_2$ and experimentally characterized. The variation of the power splitting ratio for each mode is less than 0.4 dB over the full C-band, and the excess losses of the splitter for all four modes exceed the insertion loss of a straight waveguide by less than 1.85 dB.