Lidar systems use pulses of infrared light to measure distance and map a 3D scene with high resolution, allowing autonomous vehicles to rapidly react to obstacles that appear in their path. However, traditional lidar sensors are expensive, bulky systems with many moving parts that degrade over time, limiting their deployment. A new study from MIT researchers proposes a novel design for a silicon-photonics chip that could enable next-generation lidar sensors that are compact, durable, and have no moving parts. The key advancement is an integrated antenna array design that minimizes unwanted crosstalk between antennas, allowing a lidar chip to scan a wider field of view while maintaining low-noise operation compared to other silicon-photonics-based methods. This innovation could drive the development of advanced lidar sensors for demanding applications such as autonomous vehicle navigation, aerial surveying, and construction site monitoring.
Traditional lidar systems map a scene using a bulky box that spins to send pulses of light in multiple directions. In contrast, silicon-photonics-based lidar sensors systematically scan an emitted light beam in multiple directions non-mechanically using an integrated optical phased array (OPA). The OPA relies on an array of integrated antennas with tiny perturbations along their length, allowing them to scatter light from an input source. By adjusting the phase of light routed to each antenna, researchers can change the angle at which the light is emitted.
However, if antennas are too close together, they will couple with each other, causing the emitted light to become jumbled. To avoid this, scientists typically space antennas farther apart, but this leads to multiple copies of the light beam at different angles, limiting the field of view. MIT researchers addressed this issue by designing reduced-crosstalk antennas that can be placed closer together without significant coupling. They created three antennas with different geometries, varying their widths and the size and arrangement of corrugations, allowing each antenna to have a different propagation coefficient.
To ensure that the antennas emit light in the same way despite their different geometries, researchers designed the antennas to meet three parameters: each antenna must emit the same amount of light, each must emit a beam at the same angle, and the emission angle must change uniformly across the array. By successfully fabricating the OPA with reduced-crosstalk antennas spaced significantly closer than traditional designs, they demonstrated accurate beam steering across a wide field of view without grating lobes.
In the future, researchers aim to further improve their technique for an even wider field of view and explore new potential solutions discovered during the development of the underlying theory. This work addresses a longstanding challenge in integrated optical phased arrays and represents a significant step forward for chip-scale, solid-state beam-steering technology.
Blogger's Review: This breakthrough showcases the immense potential of photonics technology in the lidar domain, particularly its significance in demanding applications like autonomous driving. By overcoming the limitations of traditional lidar with innovative antenna design, the researchers lay the groundwork for future intelligent transportation systems. Excited to see further advancements and real-world applications of this technology.