On-chip 2D beam-steering with a liquid-crystal-tunable optical phased array

Optical phased arrays (OPAs) with the ability of dynamic beam-steering hold great promise for industrial applications. Although they potentially offer high-resolution, high-speed and wide-angle beam-steering, 2D beam-steering has only been achieved by 1D OPAs with wavelength-tuning or by 2D OPAs containing enormous numbers of elements, thereby significantly increasing the system complexity and power consumption. Here we demonstrate a liquid-crystal-tunable Bragg-reflector waveguide outcoupler integrated with a 1D OPA. The output beam angle is controlled by an electric-field applied to the liquid crystal between the Bragg-mirrors, independently from steering along a second axis with the OPA. Our proof-of-concept demonstration with an 8-channel OPA shows 2D beam-steering with a 16° × 15° field-of-view and 12 ms × 14 μs time-response. Our approach opens a practical way for scalable OPAs capable of single wavelength 2D beam-steering, as well as demonstrating a strategy for the integration of liquid crystal materials with silicon photonics.