Compact and Ultra-Broadband Silicon Photonic Adiabatic Directional Coupler Using Rib Waveguides

An ultra-broadband and compact 3-dB power splitter has been designed and fabricated using an adiabatic rib silicon waveguide on the silicon-on-insulator (SOI) platform. This device primarily consists of two tapered rib waveguides to facilitate mode evolution for the transverse electric (TE) mode. The results demonstrate that the proposed device can achieve a 150 nm bandwidth in the wavelength range from 1450 nm to 1600 nm for 3-dB power splitting. In addition, the mode evolution footprint is significantly reduced to 78~\mu \text{m} with an excess loss of less than 0.18 dB. This proposed device offers a notable trade-off of device performance for power splitters. With multiple performance metrics, the rib waveguide-based adiabatic directional coupler exhibits significant potential for application in high-density photonic integrated chips (PICs).