61-Port Fan-Shaped Ge-on-Si Photodetector for Large-Scale Waveguide-Multiplexed Photonic Matrix-Vector Multiplication

Multiport photodetectors (PDs), which sum multiple optical signals, play a critical role in waveguide-multiplexed photonic matrix-vector multiplication (MVM). To date, only relatively small-scale multiport Ge-on-Si PD with up to 16 ports has been demonstrated. Scaling the number of PD ports requires increasing the Ge width, which inevitably enlarges the Ge area and leads to a slower response speed and higher dark current. In this work, we propose a novel fan-shaped geometry and shorten the Ge length to reduce the Ge area. Using the new design, we demonstrate a 61-port PD that achieves a 3-dB bandwidth of 16.4 GHz and a dark current of 15.1 nA at −3 V bias. Furthermore, we compare the multiport PD with the single-port PD array and demonstrate the advantages of the multiport PD in terms of the response speed and dark current. This work reports the largest-scale multiport PD to date, paving the way for a large-scale photonic MVM based on waveguide multiplexing.