【作者】 王喆超；

【导师】 何赛灵；

【作者基本信息】 浙江大学 ， 光学工程， 2010， 博士

【摘要】 经过多年发展,硅光子学如今已经成为受到广泛关注的热点研究领域。利用硅的高折射率差和成熟的制造工艺,硅光子学被认为是实现高集成度光子芯片的最佳选择。但是,硅光子学也有其固有的缺点,比如缺乏高效的硅基有源器件,极低的光纤-波导耦合效率以及硅基波导显著的偏振相关性等都制约着硅光子学的进一步发展。本论文针对这些问题,试图通过新的尝试给出一些全新的解决方案。首先我们回顾了一些光波导的数值算法,并在此基础上开发了一个基于柱坐标系的有限差分模式分析器,它非常适合于分析弯曲波导的本征模场。对于复杂光子器件结构的分析,我们主要利用时域有限差分以及波束传播法等数值工具。接着我们回顾了硅基光子器件各项主要的制造工艺和测试技术。重点介绍了几种基于超净室设备的关键工艺,如等离子增强化学气相沉积,电子束光刻以及等离子体干法刻蚀。为了同时获得较高的耦合效率以及较大的对准容差,本论文主要利用垂直耦合系统作为光子器件的主要测试方法。针对不同的硅波导结构,我们提出并且实验验证了两款新型耦合器以提高硅波导的耦合效率。一款基于非均匀光栅的垂直耦合器,在实验中,我们得到了超过60%的光纤-波导耦合效率。此外,我们还开发了一款用以实现硅条形波导和狭缝波导之间高效耦合的新型耦合器,理论设计和实验结果都证明该耦合器可以实现两种波导之间的无损光耦合。为了消除硅基无源器件显著的偏振相关性,我们首先利用一种特殊的三明治结构波导,通过优化多层结构,成功消除了一个超小型微环谐振器中心波长的偏振相关性。同时,我们分析了另外一种可以有效消除偏振相关性的偏振分级方案,并提出了两种新型结构以实现该方案中的两种关键元件。通过理论分析以及实验验证,一个基于一维光栅的偏振分束器被证明能够实现两种偏振光的有效分离。该分束器同时还能作为光纤与硅波导之间的高效耦合器。实验中我们获得了超过50%的耦合效率以及低于-20dB的偏振串扰。我们还对一个基于硅条形波导的超小型偏振旋转器进行了理论分析,该器件能够实现100%的偏转转化效率,并拥有较大的制造容差。在本论文中,我们还对利用侧向外延生长技术实现Ⅲ-Ⅴ材料与硅材料混集成的可行性进行了初步分析,并优化了诸如氢化物气相外延,化学物理抛光等关键工艺。在该方案中,二氧化硅掩膜被用来阻止InP种子层中的线位错在外延生长中的传播。初步实验结果和理论分析证明该集成平台对于实现InP和硅材料的混合集成具有很大的吸引力。更多还原

【Abstract】 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.更多还原