Flat Emission Silicon Nitride Grating Couplers for Lidar Optical Antennas

Light detection and ranging (Lidar) is a key enabling technology for autonomous vehicles and drones. Its emerging implementations are based on photonic integrated circuits (PICs) and optical phased arrays (OPAs). In this work, we introduce a novel approach to the design of OPA Lidar antennas based on Si3N4 grating couplers. The well-established TriPleX platform and the asymmetric double stripe waveguide geometry
with full etching are employed, ensuring low complexity and simple fabrication combined with the low-loss advantages of the platform. The design study aims to optimize the performance of the grating coupler-based radiators as well as the OPA, thus enhancing the overall capabilities of Si3N4-based Lidar. Uniform and non-uniform grating structures are considered, achieving θ and φ angle divergences of 0.9◦ and 32◦ and 0.54◦ and 25.41◦, respectively. Also, wavelength sensitivity of 7◦/100 nm is achieved. Lastly, the fundamental OPA parameters are investigated, and 35 dBi of peak directivity is achieved for an eightelement OPA.