Inverse design of a dual-mode 3-dB optical power splitter with a 445 nm bandwidth

Optical power splitters are fundamental blocks for photonic integrated circuits. Conventional 3-dB power splitters are either constrained to single-mode regime or to the limited optical bandwidth. In this paper, an alternative design approach is proposed via combined method of topology optimizations on both analog and digital meta-structure. Based on this approach, a dual-mode power splitter is designed on silicon-on-insulator with an ultra-broad bandwidth from 1588 nm - 2033nm and an ultra-compact footprint of only 5.4 µm × 2.88 µm. The minimum feature size is 120 nm which can be compatible with silicon photonic foundry process. The simulated excess loss and crosstalk over this wavelength range for the two lowest TE modes are lower than 0.83 dB and -22 dB, respectively. To the best of our knowledge, this is a record large optical bandwidth for an integrated dual-mode 3-dB power splitter on silicon.