A Monolithically Integrated Large-Scale Optical Phased Array in Silicon-on-Insulator CMOS

Abstract

A large-scale monolithic silicon nanophotonic phased array on a chip creates and dynamically steers a high-resolution optical beam in free space, enabling emerging applications in sensing, imaging, and communication. The scalable architecture leverages sub-array structure, mitigating the impact of process variation on the phased array performance. In addition, sharing control electronics among multiple optical modulators in the scalable architecture reduces the number of digital-to-analog converters (DACs) required for an $N^{2}$ array from $\mathcal {O}(N^{2})$ to $\mathcal {O}(N)$ , allowing a small silicon footprint. An optical phased array for 1550-nm wavelength with 1024 uniformly spaced optical grating antennas, 1192 optical variable phase shifters, and 168 optical variable attenuators is integrated into a 5.7 mm $\times$ 6.4 mm chip in a commercial 180-nm silicon-on-insulator RF CMOS technology. The control signals for the optical variable phase shifters and attenuators are provided by 136 DACs with 14-bit nonuniform resolution using 2.5-V input-output transistors. The implemented phased array can create 0.03° narrow optical beams that can be steered unambiguously within ±22.5°.