Key building block optimization for high-performance transceivers: Multimode interferometers from conventional to sub-wavelength regime

Multimode interferometers (MMIs) are key components for high-bandwidth transceivers in upgrading the data transmission of future detector systems. We present two conventional highperformance MMIs fabricated on a 250 nm SOI platform with different power splitting ratios which operate as 50%:50% power splitter for Mach-Zehnder modulators and as 86%:14% power splitter for loop control in future transceiver designs, respectively. Besides, we present the novel MMIs based on sub-wavelength gratings. By engineering the refractive index of relevant parts, more compact 50%:50% MMIs and multi-port, low phase error MMIs become feasible.