Coherent Beam Steering via a Synthetic-Aperture Integrated Waveguide Grating Antenna

The waveguide grating antenna serves as the optical-frequency counterpart of radio-frequency phased array, enabling high-speed beam steering in a fully solid-state form. It offers comprehensive advantages such as high integration, low power con-sumption, and a wide field of view (FOV). However, due to limitations in fabrication techniques, achieving large apertures along with precise phase error detection and correction remains a significant challenge. In this work, we design and fabricate a synthetic-aperture waveguide grating antenna to achieve a larger aperture, which consists of two sub-apertures with a total of 512 channels. The two sub-apertures are fed independently by external optical fibers and synthetized as separate wave-guide grating antennas. Multiple detection techniques, including target-in-the-loop optimization and digital holography, are incorporated to build a combined system for inter-aperture and intra-aperture phase errors measurement and correction. This approach establishes a complete technical framework for high-accuracy beam control using in the synthetic-aperture integrated waveguide grating antenna. High-quality synthesized beam steering over a 30° FOV is achieved. After correction, the average residual intra-aperture phase error is measured at λ/15.97, and the residual inter-aperture phase error is meas-ured at λ/39.37. The peak intensity in the steering direction is enhanced by an average factor of 46.73, and the main lobe power increased by an average factor of 11.07. The synthetic-aperture waveguide grating antenna enables large-aperture, high-quality, wide-field synthetic beam steering, providing a promising pathway toward compact, solid-state, cost-effective, and high-performance systems for applications in communication and ranging.