Solid-State Photonics-Based Lidar With Large Beam-Steering Angle by Seamlessly Merging Two Orthogonally Polarized Beams

Abstract

In a solid-stage photonics-based Lidar, all essential components are integrated into a silicon chip using silicon photonic technique. It is preferable to implement Lidar's beam steering through wavelength tuning due to its simplicity. However, a large wavelength tuning range is usually required to generate a satisfactory beam-steering angle, which usually is constrained by the limited material and waveguide dispersion. In silicon-on-insulator (SOI) waveguide, the effective index of the transverse-electric (TE) mode is significantly different from that of the transverse-magnetic (TM) mode. This allows us to design a novel device that is composed of two grating couplers optimized for two orthogonal polarizations. Two beams diffracted from two grating couplers with the orthogonal polarization can be seamlessly merged together. Combining these two orthogonally-polarized output beams significantly increases the beam-steering angle and dramatically reduces the required wavelength-tuning range.