FMCW LiDAR with a coherent receiver chip based on 3 μm SOI photonics platform

Abstract

Silicon photonics is considered as the ideal solution for chip-scale solid Frequency Modulated Continuous Wave (FMCW) Light Detection and Ranging (LiDAR). In this paper, a coherent receiver chip, integrating beam splitters, 180-degree mixers, germanium-balanced photodetectors, and an on-chip temperature sensor is presented. Benefiting from the micron-scale silicon photonics platform, the propagation loss of the waveguide is 0.19 dB/cm, and the imbalance of 180-degree mixers is only 0.30 dB at 1550 nm. The 3 dB cut-off frequency of the balanced photodetector reaches 37.3 GHz, and the responsivity is 0.32A considering the coupling loss. An FMCW LiDAR system with the coherent receiver chip is built for ranging and velocity measurement. Ranging of distance at 120 m with the precision of 0.3 m is achieved. The micron-scale silicon photonics platform can also provide the capabilities for multi-channel coherent receivers and monolithic integration of transmitters and receivers, providing another practical approach for solid state FMCW LiDAR system which can be applied to autopilot, medical and other field for their lightweight requirement.