On-chip three-mode (de-)multiplexer based on a grooved waveguide MMI coupler on an InP platform.

A compact on-chip three-mode (de-)multiplexer based on a grooved waveguide multimode interferometer (GW-MMI) coupler was demonstrated on an indium phosphide (InP) platform for the first time. Two grooves were incorporated into the GW-MMI structure to facilitate the generation of three discrete waveguides that would effectively confine the self-images and enhance the phase-matching condition between them, resulting in a significantly more compact MMI length of just 198 μm. The ridge waveguides were fabricated using a conventional contact lithography process, which is both straightforward and cost-effective. The measured insertion losses of the TE, TE, and TE modes are 2.9 dB, 7.53 dB, and 4.05 dB, respectively. Furthermore, the 3 dB bandwidths for all modes are larger than 13.5 nm in comparison to the value at 1550 nm.