Coherent Synthesis of Silicon Optical Phased Arrays toward Enhanced Power and Aperture

Optical phased arrays (OPAs) have become essential components in light detection and ranging (LiDAR) systems and free-space optical communication (FSO), where OPAs with optimized power output and aperture size are crucial for enhancing the detection range and improving signal transmission reliability. While current methods focus on utilizing high-power-tolerant waveguide materials (e.g., SiN) to boost OPA output power and increasing the number of grating antennas to enlarge the output aperture, several factors─such as on-chip tree-like beam-splitting structures, on-chip losses, and the limitations of the effective photolithographic area─restrict the achievable output power and aperture size. We demonstrate the coherent beam synthesis of multiple OPAs using off-chip phase-locked loop compensation, which results in a 319% enhancement in peak power in the far-field main lobe while achieving a 62% reduction in fwhm of the main lobe compared to that of a single OPA. Moreover, our method enables precise beam steering without the need for tedious recalibration. The demonstrated technique shows excellent scalability for modular expansion, offering a promising framework for next-generation OPA applications in long-range sensing and reliable optical communication systems.