A study on the beam steering using solid state device for LiDAR applications

Abstract

At present, extensive research is underway within the automotive industry focusing on self-driving vehicles. Consequently, there is a heightened demand for a multitude of sensors, with significant emphasis placed on sensor research. Specifically, attention is drawn to LiDAR research, poised to supersede RADAR technology, which identifies objects through radio wave detection. Within the automotive sector, Velodyne's LiDAR is currently under scrutiny as an autonomous driving sensor, utilizing a conventional methodology. Conventional LiDAR systems employ a rotating mirror mechanism for distance measurement. However, these mechanical LiDARs suffer from drawbacks such as considerable bulk, limited durability, and sluggish steering capabilities. Hence, the principal objective of this dissertation is to pioneer the development of a solid-state LiDAR sensor. The solid-state LiDAR presents advantageous features including compact size, swift scanning capabilities, durability, cost-effectiveness, and the potential for mass production. The second chapter is dedicated to exploring research on micro ring cavities tailored for comb LiDAR light sources. We specifically investigated the evanescent wave coupling of microresonators on silicon nitride platforms. Our study focuses on analyzing the geometric impact of the straight bus waveguide on microring resonator coupling. The optimized waveguide width facilitates efficient excitation of the fundamental mode within the resonator waveguide. We substantiated our findings by experimentally showcasing a quality factor microring resonator with a quality factor of 7 million comb generation. The subsequent section involves the design and characteristic analysis of the optical phased array device. Employing FDTD (Finite-Difference Time-Domain) simulations, we meticulously optimized each element of the optical phased array device. In order to minimize waveguide perturbation, a cladding grating structure, segregating the grating from the waveguide, was employed. The utilized phased array integrates a micro heater phase shifter architecture, demonstrating a steering range of 25o with an efficiency of 6%. Finally, beam steering was executed using an LCOS (Liquid Crystal on Silicon) device. According to the grating equation, a short-pitch LCOS element enables broad steering capabilities. We fabricated a device with the shortest pitch of 3.6 μm, demonstrating wide-angle steering of 15.6o.