Investigation Of Passive Silicon Photonic Devices And A Hybrid Integration Platform

Silicon photonics is now a widely studied research topic. Due to its high-index-contrast and the compatibility with the mature complementary metal-oxide-semiconductor technology, silicon photonics is a promising platform for low cost high density integration. Besides its advantages, there are still some general problems, including the lack of silicon active devices, the difficulty of light coupling, the polarization dependence, etc. This thesis aims to give some novel solutions and new attempts to address these problems.Numerical methods are reviewed first. A semi-vectorial finite-difference mode solver in cylindrical coordinate system is developed and it is very useful for eigenmode analysis of the bent waveguide. We also use the finite-difference time-domain method and beam propagation method to analyze the light propagation in complex structures.The fabrication and characterization technologies are reviewed and studied. We mainly focus on the fabrication techniques based on clean room facilities, including plasma assisted film deposition, electron beam lithography and dry etching. We mainly use vertical coupling system for characterization in this thesis, since it can provide much higher coupling efficiency and larger alignment tolerance.Two novel couplers related to different silicon waveguides are studied. In order to improve the coupling efficiency of a grating coupler, a nonuniform grating is theoretically designed and over 60% coupling efficiency is experimentally obtained. We also demonstrated another novel coupler facilitating the light coupling between silicon photonic wires and slot waveguides, both theoretical and experimental work have been done. Almost lossless coupling is achieved in experiments.In order to eliminate the polarization dependence of silicon photonic wire based devices, we proposed two different approaches. The first one is the use of a sandwich waveguide structure. By optimizing the multilayer structure, we successfully eliminate the large birefringence in an ultrasmall ring resonator. Another approach is to use polarization diversity scheme. Two key components of the scheme are studied. We theoretically analyzed and experimentally verified an efficient polarization beam splitter based on a one-dimensional grating coupler. Over 50% coupling efficiency from optical fibers to silicon waveguides for both polarizations and-20dB extinction ratio between them are experimentally obtained. A compact polarization rotator based on silicon photonic wire is theoretically analyzed.100% polarization conversion is achievable and the fabrication tolerance is also analyzed.We investigate a novel integration platform based on nano-epitaxial lateral overgrowth technology to realize hybrid integration of III-V materials on silicon. A silica mask is used to block the threading dislocations from the InP seed layer on silicon. Technologies such as hydride vapor phase epitaxy and chemical-mechanical polishing are developed. Preliminary results show that a thin dislocation free InP layer on silicon is obtained experimentally.