Ultra-compact 2 × 2 dual-mode power splitter based on a slotted subwavelength grating multimode interference coupler

We design and demonstrate a dual-mode power splitter that equally splits both the fundamental (TE0) and higher-order (TE1) modes, based on an ultra-compact multimode interference (MMI) coupler utilizing slotted subwavelength grating structures. The fabricated MMI coupler occupies a footprint of only 33 × 5 µm², which, to the best of our knowledge, is the smallest footprint reported for a 2 × 2 dual-mode power splitter. Furthermore, experimental results demonstrate favorable power-splitting characteristics over a 60-nm bandwidth, with worst-case excess losses of 0.98 dB for TE0 input and 1.38 dB for TE1 input, and modal crosstalk below -16.4 dB.