Integrated Optical Phased Arrays and Highly Efficient Spot-size Converting Coupler for LIDAR Applications

Abstract

Light detection and ranging (LIDAR) is a currently developing sensing technology that detects objects using light. The next generation of information technologies including autonomous vehicles and AI robotics all require the LIDAR sensing system due to its high resolution for a more accurate sensing than radio detection and ranging (RADAR). Currently, LIDAR systems use a mechanical based beam steering approach where multiple lasers are mounted on a mechanical apparatus which is rotated to steer the beam. The mechanical device is expensive, bulky, and large. The scanning rate of the device is limited to the physical rotation of the rotor, and that the systems fail to capture accurate data when the rotor is stuck. This device will require high maintenance and the mechanical approach makes LIDAR systems not so attractive. The approach of using Silicon-on-Insulator (SOI) based optical phased array (OPA) solves these problems by being cheap to manufacture, small in size and does not require maintenance as it does not have any moveable parts. In this thesis, the design and simulation of the optical phased array are presented. Simulation methods such as finite element method (FEM) and finite-difference time-domain method (FDTD) are used to conduct this study. The thesis demonstrates the need for crosstalk reduction and the detrimental effects it has upon the beam steering mechanism. A near half-wavelength one-dimensional (1-D) OPA antenna which incorporates a superlattice structure design is proposed which overcomes conventional crosstalk problems and offers high resolution broadband beam steering while preserving a small footprint size. The element spacing of 0.8 μm is achieved for the grating OPA and results show that the proposed OPA can steer 130° in the longitudinal axis with a divergence beam width of 2.52° at the main lobe for 33 grating elements. The thesis also describes to improve the fiber-to-chip coupling efficiency.