A 1×2 Power-Monitoring Splitter Based on a Ge/Si Hybrid MMI Structure

A 1×2 optical power splitter with power monitoring capability based on a Ge/Si hybrid structure is proposed and demonstrated. An optical power splitter based on multimode interference (MMI) is designed for silicon and a short piece of germanium (Ge) layer is then placed above the MMI structure, where the electric field is weak. Therefore, only a small portion of the input optical power is absorbed by the Ge layer for power monitoring, while transmission and splitting of light in the Si waveguide remain minimally affected. Fabricated using standard CMOS processes, the device exhibits an insertion loss of ~ 0.5 dB and a responsivity of ~ 9 mA/W at -1 V around 1550 nm. Without altering the fundamental MMI-based splitter, this design simultaneously achieves both optical splitting and power monitoring.