A silicon chip with a serpentine optical phased array (SOPA), developed by researchers at the University of Colorado Boulder, could improve the resolution and scanning speed of lidar systems while reducing bulkiness, making them scalable for a range of applications. The SOPA is based on an array of low-loss grating waveguides and supports passive, 2D wavelength-controlled beam steering. The beams are controlled by changing wavelengths. Multiple phased arrays can be controlled simultaneously to create a bigger aperture and a higher-resolution image. Compact, wavelength-steered tiles are packed efficiently into the array and do not require active control. The space-efficient design enables scalable tiling of SOPAs into large apertures. A silicon chip with an array of SOPA tiles. The 32 tiles in the 8-by-4 array have slightly differing grating designs, showing here two matching pairs of tiles “lighting up” at this viewing angle. Drawn superimposed are beams from two matching tiles and the far-field beam interference pattern demonstrating tiled beam forming. Courtesy of Bohan Zhang and Nathan Dostart. “We’ve figured out how to put this two-dimensional rainbow into a little teeny chip,” professor Kelvin Wagner said. The researchers demonstrated a SOPA tile using a 1450- to 1650-nm wavelength sweep to produce 16,500 addressable spots in a compact array. They demonstrated the tiling approach through far-field interference of beams emitted from two separate OPAs on a single silicon photonic chip. The researchers believe that the SOPA design is a promising solution for achieving easily controllable, large, 2D beam steering apertures for applications such as long-range integrated photonic lidar. A raster scan pattern addressed by wavelength-steered silicon photonic optical phased array. The curving of this pattern is an indicator of the dispersion in the on-chip waveguide system. Courtesy of Nathan Dostart. Whether it’s on top of a self-driving car or embedded inside a smartphone or augmented reality game, lidar will play a role in future technologies for consumers and business. “We’re proposing a scalable approach to lidar using chip technology. And this is the first step, the first building block of that approach,” said researcher Nathan Dostart, who will continue the work at NASA Langley Research Center in Virginia. The research was published in Optica (www.doi.org/10.1364/OPTICA.389006).