Broadband Silicon Nitride Power Splitter Based on Bent Directional Couplers with Low Thermal Sensitivity

Directional couplers, as power splitters, have provided a significant contribution for light splitting and combining in silicon photonics. However, the splitting ratio of conventional directional couplers is very sensitive to wavelength, which limits the bandwidth and the transmission performance of the devices. In this work, a silicon nitride bent directional coupler with large bandwidth, large fabrication tolerance, and low thermal sensitivity is proposed and demonstrated through simulation analysis and experiments. Moreover, the fabrication process of 400 nm thick silicon nitride photonic devices is described, which are compatible with complementary metal-oxide-semiconductor technology. The 1 dB bandwidth of the bent waveguide coupler can reach 80 nm, and the thermal sensitivity is reduced by 85% compared to the silicon-based devices.