Optical phased arrays (OPAs) are renowned for their exceptional ability to manipulate and direct light beams, positioning them as an ideal choice for solid-state light detection and ranging (LiDAR) technologies. This review provides a comprehensive examination of the current research landscape for photonic integrated circuit (PIC)-based OPAs. It begins by addressing the critical design elements at the component level necessary for optimal functionality. This review then delves into phase calibration techniques and the overarching architecture of OPAs. It concludes by emphasizing the innovative 3-D OPA design, which stands out for its enhanced optical efficiency.

The traditional photonic integrated circuit (PIC) inherits the mature CMOS fabrication process from the electronic integrated circuit (IC) industry. However, this process also limits the PIC structure to a single-waveguide-layer configuration. In this work, we explore the possibility of the multi-waveguide-layer PIC by proposing and demonstrating a 3D optical phased array (OPA) device, with the light exiting from the edge of the device, based on multi-layer Si₃N₄/SiO₂ stacks. This device is in a multi-waveguide-layer configuration at every single position of the device. This configuration offers the possibility of using edge couplers at both the input and the emitting ends to achieve broadband high efficiency, and its uniqueness provides the potential for a more extended detection range in the lidar application. The device has been studied by numerical simulation, and proof-of-concept samples have been fabricated and tested.