O‐Band Multimode Interference Coupler Power Combiner Using Slot‐Waveguide Structures

Photonic transmitters that operate with a high data transfer rate (over 150 Gb/s) at the O‐ band range (1260–1360 nm) require at least 100 milliwatts of power to overcome the power losses that are caused by using high‐speed modulators. A laser with higher power can probably handle this requirement; however, for the transmitter system, this solution can be problematic due to the nonlinear effects that can happen, which may lead to high noise in the transmitter system. Thus, to solve this issue, we propose a new design of a 2 × 1 multimode interference (MMI) power combiner using silicon nitride (SiN) slot waveguide structures. The MMI power combiner and the SiN slot waveguide structures were optimized using the full‐vectorial beam propagation method (FV‐BPM) and the finite difference time domain (FDTD) method. After combining two sources, high efficiency was obtained of 94.8–97.6% from the total power after a short coupling length of 109.81 μm over the O‐band range with a low back reflection of 44.94 dB. Thus, the proposed device can be very useful for combining two O‐band sources to gain a higher power level, which can be utilized to improve performances in transmitter systems.