Integrated solid-state lidar employing orthogonal polarizations and counterpropagation

Light detection and ranging (lidar) has attracted significant interest as a sensing technology for its ability to achieve highresolution imaging and wide-angle perception. However, conventional lidar systems, built with separate components, are often bulky, expensive, complex, and prone to instability. In contrast, solid-state lidar, based on silicon photonics technology, offers a solution with its compact size, less expense, low energy consumption, and improved reliability. However, achieving precise beam steering remains a critical challenge for integrated lidar systems. Various methods have been demonstrated for beam steering, which is one of the simplest and most efficient approaches that utilize wavelength tuning with a grating coupler antenna. In this review, we introduce the fundamental principle of optical phased array for beam steering and provide an overview of the recent advancements in integrated solid-state lidars utilizing orthogonal polarizations and counterpropagation to enhance beam-steering range and angular resolution.