【作者】 杨波；

【导师】 何赛灵； 戴道锌；

【作者基本信息】 浙江大学 ， 光学工程， 2012， 博士

【摘要】 随着光纤通信技术和光传感技术的快速发展,集成光子器件特别是集成光滤波器由于其低成本、高集成度等特点引起了广泛的关注。在LiNbO3、SiO2、 Si、InP和聚合物等各类集成光学材料中,聚合物材料在降低器件成本、减小器件损耗等方面有着巨大的优势。对于任何材料的集成光子器件,减小器件尺寸、提高集成度是一个长期的发展方向。强限制光波导是实现小型化集成光子器件的最为有效的方法。本文基于SU-8聚合物材料,对脊形光波导和悬挂式光波导两种强限制光波导,以及基于SU-8脊形光波导的小型化阵列波导光栅和微环谐振器进行了深入的理论和实验研究。回顾了光波导基本理论和几种常用的数值计算方法。首先介绍了求解平板波导的解析方法和求解条形波导的近似方法。为了精确求解复杂波导及其器件问题,必须采用数值模拟方法。对有限差分方法、光束传播方法和时域有限差分方法等几种常用的数值计算方法进行了介绍。研究了SU-8脊形光波导这种新型强限制光波导的导波特性。通过对整个工艺过程的调试,成功制作了SU-8脊形光波导。实验得到具有不同波导宽度的SU-8脊形光波导的传输损耗为0.24～0.15dB/mm。并且,验证了这种波导可承受75μm的弯曲半径,因此SU-8脊形光波导具有提高器件集成度的巨大潜力。基于SU-8脊形光波导,本文研究了阵列波导光栅(AWG)和微环谐振器(MRR)两种典型的集成光滤波器。首先对基于SU-8脊形光波导的小型化阵列波导光栅进行了设计制作。由于所用波导的强限制特性,研制出的AWG尺寸仅为基于传统掩埋型SU-8波导的同类器件的1/40,从而大大提高了器件集成度。通过选取合适的波导尺寸,成功消除了AWG的偏振相关性,使TE和TM模式的信道中心波长重合。热光调谐研究表明,所研制的AWG滤波器具有调谐效率高、大范围可调等优势。另外我们还研究了基于SU-8脊形光波导的微环谐振器。采用耦合区波导的宽度进行局部减小的设计,研制出了小型化MRR,并对其光谱特性进行了表征。为了进一步增加光场限制,减小波导的弯曲半径,提高器件集成度,我们对SU-8脊形光波导进行了结构改进。通过将SU-8脊形光波导的Si02下包层腐蚀掉,获得了在侧向和纵向都为强限制型的悬空波导,其弯曲半径可以小至7gm,比相应的脊形光波导小一个数量级。为了实现这种超高集成度的悬空型光波导,研制出低损耗(<0.1dB)的支撑臂结构。基于这种悬空型光波导制作出微盘谐振器,获得了较大自由光谱范围和高消光比的响应特性。更多还原

【Abstract】 As optical communication and sensing technologies progress rapidly, optical integrated devices, especially optical filters, attract more and more interests because of their low cost and compactness. Among various materials for optical integration, polymer shows superior performances in terms of cost reduction and low loss. On the other hand, to achieve lower cost and better performance, higher integration density is desirable for optical integrated devices, where the strongly confined waveguide with a high refractive index contrast is a prerequisite. In this work, two kinds of strongly confined SU-8polymer waveguides, namely, ridge and suspended waveguides are studied systematically. Based on these waveguides, two typical optical filters, i.e., arrayed waveguide gratings (AWG) and microring resonators (MRR), are developed for practical use.The fundamentals of optical waveguides are briefly reviewed. While the slab waveguide mode can be solved analytically, numerical simulation is necessary to solve waveguide problems with more complex situations. Several numerical simulation methods, such as finite difference method (FDM), beam propagation method (BPM), and the finite-difference time-domain (FDTD) method, are introduced. These methods are intensively used in the following.The SU-8polymer ridge waveguides with strong light confinement are studied. The fabrication process is optimized and the fabricated waveguides perform well with a low loss of0.24～0.15dB/mm. According to the measurement results, this kind of waveguide can afford a bending radius as small as75μm, indicating its large potential to increase the integration density.Two typical optical filters, i.e., AWG and MRR, are realized based on the SU-8polymer ridge waveguides. By using this strongly confined waveguide, the fabricated AWG is only1/40in size of that based on the traditional buried SU-8polymer waveguide, showing a considerable increase of the integration density. By adjusting the size of the waveguide, the polarization dependency is eliminated. Besides, the present AWG shows fairly good thermal-optic tuning performances in terms of a high tuning efficiency and a large tuning range. MRR based on SU-8polymer ridge waveguides is also investigated. The waveguides in the coupling region are locally narrowed to improve the light coupling while maintaining a reasonable gap size. The spectral response of the fabricated MRR is characterized. To further enhance the light confinement and reduce the device size, we developed the SU-8suspended waveguide by etching away the buffer layer of the SU-8ridge waveguide. Since this waveguide is strongly confined in both lateral and vertical directions, the bending radius can be reduced to7μm, which is an order smaller than that of the ridge waveguide. While crossing structures (as the supporting elements) are inevitable to realize the suspended waveguide, low-loss (<0.1dB) supporting structures are developed. The microdisk resonators based on the suspended waveguide are fabricated and show a large free spectral range and a high extinction ratio.更多还原