【作者】 尹锐；

【导师】 王明华；

【作者基本信息】 浙江大学 ， 微电子与固体电子学， 2001， 博士

【摘要】 光网络的飞速发展，对光信息处理器件的要求越来越高，光子器件的集成变得越来越迫切。本论文的工作是针对两个重要的光子器件—在光网络中必不可少的光开关列阵和能够实现许多光信息处理功能的多模干涉器(MMI)进行集成化研究。其中对光开关列阵的研究主要是通过提高开关单元的消光比和优化列阵结构来扩大其路数和集成度；对MMI干涉器的研究则是改善现有器件的结构以使其能够与多数波导器件实现工艺和结构上的兼容而方便地集成在一起。 在光开关列阵方面，采用速度快、无偏振依赖性的电流注入全内反射机理来实现光的转向。通过对带填充效应、带隙缩小效应和自由载流子吸收效应的分析，得到GaAs材料在0.8μm～1.6μm范围内注入所引起的折射率变化规律。以此为基础对非对称Y分支结做参数优化，将其消光比提高了10dB，单元结构的这个结果有利于列阵的大路数化。在列阵结构方面提出了正交结构光开关列阵，对连接圆弧波导的分析表明此正交结构可将相邻波导的间距缩小为250μm，具有很强的集成潜力。结合优化的单元结构，4×4正交结构光开关列阵的消光比可达25dB以上，串话可达45dB以上。 MMI干涉器的集成化研究方面，传统的MMI干涉器都是深腐蚀强限制波导结构的，而其他多数光波导器件则多为弱限制和具有凸形的渐变边界结构的波导，因此本文研究的主要方向就是弱限制和渐变边界结构在MMI方面的应用分析。为此本文首创了传播常数偏差判定法，它直接从自映像的机理出发，对干涉区内各阶模传播常数的排列情况进行分析，以此来判断自映像的效果。用这个方法分析上述两种结构的结论是，弱限制和凸的渐变边界结构不仅可以应用在MMI干涉器上，而且都能够在一定程度上改善自映像的效果，在增加MMI干涉器与其他器件的兼容性的同时提高其性能：1．对弱限制结构的进一步分析表明，在某个特定的折射率差下自映像的效果最好。 为了求出这个最佳折射率，本文以减少高阶模、近截止模式的传播常数偏差为 出发点，推导出了求解最佳折射率差的公式，这个公式的结果是目前所见的文 献中最好的。以此为基础设计了优化的弱限制1×32MMI功分器，损耗和不均匀 度分别为0.026dB和0.005dB，若采用传统的强限制结构，则分别为1.443dB、 2.049dB。2．在凸形渐变边界结构的分析中，提出了基于指数的渐变边界和梯形截面两种新 型结构的干涉区。前者在合适的参数下可以实现近似理想的自映像，具有很强 的理论指导意义；后者虽在性能方面比不上前者，但在实际工艺的可实现性方 面具有很大优势。在实现2波长波分复用(WDM)时，理想自映像可以达到50dB 左右的对比度，基于指数的渐变边界结构可以达到50.7dB，梯形截面结构可以 达到近47dB，而采用传统的强限制结构，则只有30dB。更多还原

【Abstract】 The integration of photonic device becomes more and more important due to the fast developing optical network. In this dissertation, we study the integration properties of two important photonic devices: optical switch array (the key component of optical network) and multirnode interference (MMI) coupler (it can realize many functions in optical signal processing). One purpose of this study is to enhance the integration ability of optical switch array, which can be realized by increasing the extinction ratio of the switch unit and optimize the array structure. The other purpose is to improve the compatibility between MMI coupler and most waveguide devices. This can be realized by adopting new interference structure.Current-injection total-internal-reflection (TIR) is applied to the switch due to its non-polarization dependent and high-speed property. Considering bandfilling, bandgap shrinkage and free-carrier absorption, the carrier-induced index change of GaAs is analyzed between 0.8|im~1.6jim. The asymmetrical Y-branch is optimized and the extinction ratio is increased more than lOdB. We bring forward perpendicular optical switch, which has strong integration potential. The distance between adjacent waveguide can be as small as 250(j.m. The extinction ratio of 25dB and crosstalk of 45dB is obtained in such a 4x4 array.Conventional MMI coupler is normally fabricated on deeply etched, high-index-contrast waveguide structure, while most other waveguide devices are weak-confined or gradual-bulge-edge structures. So the study on MMI coupler is the combination of MMI and weak-confined waveguide or MMI coupler and gradual-bulge-edge waveguide. The propagation-constant-error judgement method is brought out for the first time to analyze those modes in the MMI region. Results show that self-imaging can be improved by the introducing of weak-confined or gradual-bulge-edge waveguide. This means with the enhanced compatibility of MMI coupler, the performance can be improved at the same time:1. Further study shows that weak-confined MMI coupler reach the best performance under certain index contrast. An equation to solve this optimal index contrast is gained by decrease the propagation constant errors of high-order modes in the MMI region, which has the best resultcompared to other reported researches. For an optimized weak-confined 1x32 MMI splitter, the loss and uniformity are 0.026dB and O.OOSdB, respectively. As for the case of strong-confined one, the values are 1.443dB and 2.049dB, respectively.2. During the study on gradual-bulge-edge waveguide structure, we bring forward two new structures that can be applied to MMI coupler: grade-index-edge based on exponential function and waveguide with trapeziform cross-section. The first structure can nearly realize ideal self-imaging under appropriate condition, while the second structure has the advantage of easy fabrication. In the case of a 2-wavelength WDM, there is the contrast of about 50dB according to ideal self-imaging. The value of 50.7dB and 47dB are gained in the first and second structure, respectively, While in the case of conventional strong-confined structure, the contrast is only about 30dB.更多还原