Design and simulation of three-dimensional hologram emitting phased arrays in the near field

Abstract

Silicon photonics technology is gaining attention in both research and industry because of its potential to revolutionize optical components and systems while utilizing the well-established silicon semiconductor fabrication processes. Similarly, three-dimensional holography technology is emerging to build the foundation for three-dimensional displays, interfaces, and many other applications. This work attempts to combine these two technologies to generate a method to design a phased array that will emit three-dimensional holograms and investigate the scalability of the phased arrays. This thesis will cover the design and functionality of optical phased arrays and how they have been previously used to emit patterns in the far field. It will then explore three-dimensional hologram theory to prompt its incorporation into a phased array design. In order to accomplish three-dimensional holograms, this design technique takes advantage of the fact that the near field allows for multiple planes of focus, as opposed to the single focal pattern of the far field. A three-dimensional hologram can then be generated by breaking it up into planes and having the phased array recreate them by emitting the patterns that come into focus at different distances from the array. The method to do this involves back propagating desired output planes using Fresnel Diffraction and superimposing the back propagated electric fields to generate the required phased array parameters to emit such a field. This work will then explore simulation results required to design the system and various techniques to improve the process and output quality. The proposed design increases the size of the array by four times our previous designs, requiring three-dimensional Finite-Difference Time-Domain (FDTD) simulations to provide a wider range of coupling. These additional coupler simulations also prove to be critical as this proposed design alters both the amplitude and phase of each antenna in the array, which can be controlled by these couplers. We demonstrate the flexibility of the design by designing and simulating multiple output patterns as well as at varying wavelengths.