Silicon optical phased array transceivers for lens-less LiDAR application

Abstract

LiDAR (light detection and ranging) is a technology that detects distance using light, and has recently been spotlighted in various applications such as autonomous vehicles and small robots. Among them, OPA (optical phased array) have various advantages because it can be manufactured at a chip level through a CMOS-compatible process. Previously, a LiDAR system was constructed by using OPA as a component that emits light in a desired direction, but recently, studies using OPA as a light receiving element have also been proposed. In this paper, a LiDAR system capable of measuring distance by performing transmission and reception functions simultaneously using a single OPA is proposed and verified through experiments. First, the OPA device for a LiDAR system was designed and fabricated to beam scanning experiments. The design of the electro-optic p-i-n phase shifter was optimized in consideration of the phase tuning efficiency and optical loss. And the high-speed, low-power beam scanning operation was verified with the OPA using such electro-optic phase shifter. In addition, the phase control of OPA and the possibility of continuous beam scanning were discussed by calculating the phase error caused by the fabrication error in the Si-based optical devices. Using the same OPA element, receiving operation was also verified and finally the bidirectional LiDAR system that simultaneously performs transmission and reception operations based on one OPA is implemented. The single-OPA-based bidirectional LiDAR system can measure distances in a wide angular range and could utilize the coherent detection methods such as FMCW. Such bidirectional LiDAR system can become a core technology for next generation OPA-based LiDAR which provides high-precision performance and compact footprint.