【作者】 盛振；

【导师】 何赛灵； 戴道锌；

【作者基本信息】 浙江大学 ， 光通信技术， 2010， 博士

【摘要】 信息和通信技术的发展彻底改变了人们的思维方式和生活方式,促进了经济和社会的飞速发展。而光通信的诸多优势使得人们希望这项技术不仅仅局限于长距离通信方面的应用,而应该延伸至中短距离通信以及互连领域。由此,光通信及光互连中大量使用的集成光电子器件的研究吸引了越来越多的注意力。在降低成本和提高性能的愿望驱使下,集成光电子器件朝着高集成度的方向不断发展。在减小器件尺寸方面,采用高折射率差的光波导成为最直接有效的途径；在功能集成方面,将所有光功能集成在硅基材料中具有无可比拟的成本优势和诱人的发展前景。本论文紧紧围绕提高集成度的上述两个方面展开研究和讨论。首先回顾了光波导基本理论,在用解析方法求解平板波导的同时介绍了波导的各种重要概念。为了精确求解复杂的光波导及其集成器件问题,必须采用数值模拟方法。对各种常用数值计算方法进行了介绍,包括有限差分方法、光束传播方法和时域有限差分方法。研究了三种新型硅基强限制微纳光波导。通过调试并改进深刻蚀工艺,成功制作出了深刻蚀二氧化硅脊形光波导,实验中验证了这种波导可承受数十微米的弯曲半径,具有提高器件集成度的巨大潜力。根据不同的波导宽度,其传播损耗为0.33～0.81dB/mm,而侧壁散射是传播损耗的主要来源。基于这种波导,制作出了多模干涉耦合器,初步探索其在制作实际器件方面的应用价值。为了降低成本,制作并测试了SU-8聚合物脊形光波导及器件,如Y分支、微环谐振器、阵列波导光栅等。研究了硅纳米线光波导在极小弯曲半径下的弯曲损耗特性。通过比较各种数值计算方法,确定三维时域有限差分方法在此计算中是必要且可行的,并由此计算出弯曲损耗随波导尺寸和结构的变化关系。还进一步给出了微环谐振器的本征Q值与弯曲半径的关系。基于硅纳米线光波导,本文研究了阵列波导光栅、微环谐振器等两种典型集成光滤波器。首先对硅纳米线阵列波导光栅进行了优化设计。通过在阵列波导末端引入双锥形辅助波导,并采用新型混合方法对辅助波导进行快速而精确的结构优化,有效改进了器件的通道均匀性。在不增加器件尺寸的情况下,使阵列波导光栅的可用通道数增加了50%。而为了采用硅纳米线光波导实现超高密度波分复用器(通道间隔0.1nm),我们选用微环谐振器阵列这一设计方案。通过合理设计,使单个微环谐振器的光谱响应达到系统要求,制作出的器件的Q值为4×104。考虑到实验工艺误差,我们还制作了微加热器,通过热光调谐的方式分别调节每个单元的谐振波长,从而使相邻微环谐振器的谐振波长间隔符合设计值0.1nm。实验结果表明,热光调谐方式可以方便的实现这一目标,且几乎不会改变原有的光谱响应形状。为了降低光集成器件的成本及满足多功能集成的要求,需要把各种光功能器件集成在硅基材料上。由此引入了Ⅲ-Ⅴ族材料和硅基的异质集成技术。我们对异质集成技术的研究现状进行了讨论,并重点介绍本文所采用的以BCB聚合物为粘合剂的晶片粘合工艺。通过这一技术并采用倏逝波耦合方式,我们研制了SOI基InGaAs PIN型探测器。在器件设计阶段,为了消除电极对光的有害吸收以及满足光耦合的相位匹配条件,分别对电极结构和本征吸收层厚度进行了改进或优化。制作出的器件具有优良的性能：暗电流～10pA,响应率1.1A/W,并且响应谱宽可以覆盖整个S、C、L通信波段。更多还原

【Abstract】 The progress of information and communication technology has significantly changed people’s life style, and promoted the rapid development of economy and human society. While optical communication has dominated today’s long-haul communication, it is expected to extent its application to access network and interconnects. Accordingly, photonic integrated devices, which have been widely used in optical commnication, are attracting more and more research attention. To achieve lower cost and better performance, higher integration density is desirable for photonic integrated devices. While using waveguides with high refractive index contrast is a main method to reduce the size of photonic integrated circuits (PIC), integrating all kinds of optical functions on silicon substrate is the most promising way in terms of functional integration because of its unsurpassable low cost. This thesis is focused on on the above two aspects of increasing PIC’s integration density.Firstly we briefly review the fundamentals of optical waveguides. The slab waveguide mode is solved analytically, while the basic concepts of waveguides are introduced. Numerical simulation is necessary to solve waveguide problems with more complex situations. Various numerical simulation methods are introduced, including finite difference method (FDM), beam propagation method (BPM), and the finite-difference time-domain (FDTD) method.Three kinds of silicon-based waveguides with high index contrast are investigated. By exploring and optimizing the deep etching process, the deeply-etched SiO2 ridge waveguides are fabricated for the first time. According to the measurement results, this kind of waveguide can afford a bending radius as small as several tens of microns. With different core widths, the propagation loss ranges from 0.33 to 0.81dB/mm and the sidewall scattering is the main source of loss. Multimode interference couplers based on the deeply-etched SiO2 ridge waveguide are also fabricated and show fairly good performances. For lower cost, SU-8 polymer ridge waveguide and devices are fabricated, including Y-branches, arrayed waveguide gratings (AWG) and microring resonators (MRR). Ultrasharp SOI (silicon-on-insulator) nanowire bends (with a bending radius of R<2μm) are analyzed numerically. We have found 3D-FDTD method is necessary and feasible for this simulation after comparing different numerical methods. Subsequently, the bending losses of different waveguide sizes and structures are determined. The relationship between the intrinsic Q-factor of an MRR and the bending radius is also obtained.We investigate two typical kinds of optical filters, namely, AWG and MRR, based on silicon nanowire waveguides. Firstly, dual-tapered auxiliary waveguides at the exit of the waveguide array are introduced to improve the channel uniformity of a Si-nanowire-based AWG demultiplexer. By using a hybrid simulation method, the dual-tapered auxiliary waveguides of the AWG demultiplexer are optimized reliably and efficiently. As a result, the total number of channels allowed in the designed AWG demultiplexer is 50% more than that of the conventional one. Then we demonstrate the design, fabrication and measurement of the SOI MRR suitable for ultra dense WDM applications with a channel spacing of 0.1 nm. The demultiplexer is realized by cascading MRR with different resonant wavelengths. The fabricated MRR has a Q-factor of 4×104. In order to ensure that the resonant wavelength difference between neighbouring MRR is 0.1nm, we introduce micro-heaters and separately tune the resonant wavelength of each MRR by using a thermal-optic effect.Integrating III-V materials on Si is a promising candidate to realize both passive and active optical functionalities on a single silicon chip. Various heterogeneous integration technologies are reviewed with an emphasis on the adhesive die-to-wafer bonding process that we adopt. By using this technology, we investigate an InGaAs PIN photodetector integrated on SOI waveguides. The light is evanescently coupled from the SOI waveguide to the photodetector. The serious light absorption by p-contact layers is greatly reduced by introducing a central opening on these layers. The thickness of the i-InGaAs layer is also optimized towards phase matching between the SOI waveguide mode and the detector mode. The fabricated photodetector performs well in terms of very low dark current (～10pA), high responsivity (1.1A/W), and a wide wavelength range covering the whole S, C and L communication bands.更多还原