【作者】 廖进昆；

【导师】 张晓霞；

【作者基本信息】 电子科技大学 ， 光学工程， 2015， 博士

【摘要】 随着宽带光纤通信技术的飞速发展,人们对光波导电光调制器的性能指标提出了越来越高的要求。作为光通信系统中的关键器件,不仅在调制速率方面对其提出了更高的要求,同时还希望具有尽可能低的半波电压和高的稳定性。有机聚合物电光材料以其介电常数低、电光系数大等突出优点,对于制备高速宽带、低驱动电压电光调制器具有明显的优势。此外,有机聚合物还因具有制作工艺简单、传输损耗低、与光纤耦合损耗低等优点,在光波导器件中得到了广泛的应用。目前,有机聚合物电光材料已成功应用于电光调制器、光开关、可调衰减器、滤波器、多模干涉分束器等器件中,大幅度地提高了光器件的性能。电光调制器除应用于光通信系统之外,还应用于微波光子学、光控相控阵雷达等先进光电系统中。通常,在光通信系统中多用调制器单元器件,而在相控阵雷达等系统中还对阵列调制器具有较强的需求。对于有机聚合物电光材料,由于利用旋涂工艺易于实现光波导器件的平面集成和垂直集成,这对阵列电光调制器的制备具有十分重要的意义。本文针对有机聚合物材料的特点,以实现X波段微波信号的宽带传输为目标,提出了一种电极带斜坡过渡的Mach-Zehnder干涉仪型电光调制器结构,并对器件进行综合设计仿真。在此基础上,对电光调制器单元器件进行制备和测试,其半波电压为11.4V；与此同时,还对有机聚合物电光阵列调制器进行了设计和制备,验证了制备工艺的可行性。本论文的主要研究内容包括：1.研究了有机聚合物脊型光波导中影响传输损耗的主要因素：吸收和散射的物理机制,并建立了有机聚合物光波导传输损耗测量系统。研究分析了有机聚合物电光材料光学活性的物理成因,并研究了简单反射法测量电光系数的原理和误差来源,推导出精度较高的电光系数表达式,搭建了电光系数测量系统。合成并表征了新型电光有机聚合物FFC/PSU,其电光系数大于130pm/V。2.研究了有机聚合物脊型光波导的模场分布和色散特性,提出单参数变分有效折射率法并分析了聚合物多模光波导的模场分布并利用矢量波动方程对TE、TM模的色散特性进行偏振修正。对Mach-Zehnder干涉仪结构光波导中TM模的传输特性,在运用有限差分束传播法(FD-BPM)分析的基础上还研究了运用算子展开束传播法(OE-BPM)对M-Z光波导传输特性进行更为细致的分析。在上述工作的基础上,为电光调制器设计了单模工作的Mach-Zehnder干涉仪并优化了结构参数。3.研究了微带线、共面线的传输特性,分析了特性阻抗与结构参数的依赖关系。在此基础上对微带线到共面线的宽带过渡结构进行了研究,对宽带高速电极获得满足指标要求的具体结构。与此同时,还提出了新型的带斜坡的微带线到共面线宽带过渡结构,经仿真其特性得到显著提高。4.研究了有机聚合物Mach-Zehnder构型电光调制器的物理、数学模型,重点研究了电光相互作用对器件调制带宽的影响。在Mach-Zehnder电光调制器的设计中,对具有不同脊形波导结构、电极结构电光调制器的性能进行了分析和比较,综合优化了器件性能。5.研究了有机聚合物电光调制器的制备及其相关工艺。重点研究了利用旋涂、光刻和反应离子刻蚀工艺制备脊形光波导；利用溅射(蒸发)、腐蚀和电镀制备厚金电极；对极化工艺和极化稳定性进行了较细致的研究。综上所述,本文针对电光有机聚合物光波导调制器进行研究,合成表征了新型电光聚合物材料FFC/PSU其电光系数大于130pm/V；提出用单参数变分有效折射率法带偏振修正的方法分析脊型光波导的光场分布与色散特性,并对算子展开束传播法进行加速处理显著提高了计算速度；提出斜坡过渡的微带线到共面线的电极宽带过渡结构,改善了电极的传输特性,明显地提高了电光调制器的调制带宽。在此基础上,对有机聚合物电光调制器和阵列调制器进行制备和测试,验证了相关理论结果的有效性与合理性。更多还原

【Abstract】 With the rapid developments of wideband fiber optic communication technologies, the demands of high-performance optical waveguide electro-optic (EO) modulators are urgently increased due to the widespread applications. As an indispensable device in optic communication system, the modulator of high modulation rate is required in advanced networks, meanwhile the as low as possible Vπ and high stability are also expected for the modulator.Organic/polymer electro-optic materials have prominent advantages over inorganic materials such as low dielectric constant, large EO coefficient that they have promising potential to fabricate high-speed, low drive voltage EO modulators. Moreover, polymer EO materials are broadly applied in optical waveguide devices duo to the simple fabrication process, low propagation loss and low coupling loss with optical fiber. At present, organic/polymer EO materials have been successfully used in optical devices such as EO modulator, optical switch, tunable attenuator, optical filter and MI splitter etc., enhancing the performances of optical devices substantially.Besides being applied to optic communication systems, EO modulator is also used in advanced opto-electronic systems such as microwave photonics and optical phase controlled array radar systems. Generally, the unit modulator is used in optic communication system, while the arrayed device is demanded intensely in optical phase controlled array radar system. Organic/polymer EO materials are apt to realize planar and vertical integration of optical waveguide devices by spin-coating process, which is favorable for the fabrication of arrayed EO modulator.Considering the characteristics of organic/polymer materials, a novel Mach-Zehnder EO modulator with slope transition electrode is proposed to propagate broadband microwave signal in X band. Based on the results of synthetical design and simulation, the unit device of EO modulator has been fabricated successfully. The measurement indicates that the Vπ is 11.4 V. Furthermore, the feasibility of fabrication process for arrayed modulator is verified by organic/polymer EO materials.The main research work in the thesis is as follows:1. The dominent factors affecting propagation loss in organic/polymer optical rib waveguides are investigated, i.e., the mechanism of propagation loss involves absorption and scatter mainly. Also, the measurement system of propagation loss in organic/polymer waveguides has been established. The physical mechanism of optical activity of organic/polymer EO material is analyzed, and the principles and errors of simple reflection method to measure EO coefficients of polymer materials are studied. Moreover, the expression of EO coefficient with high precision is deduced strictly, and the measurement system of EO coefficient is set up successfully. A novel EO organic/polymer material FFC/PSU has been synthesized and characterized. The EO coefficient of FFC/PSU is as large as 130pm/V.2. The distributions of optical field and dispersion characteristics are analyzed for fundamental and higher order modes of organic/polymer optical rib waveguides. The distributions of optical field are analyzed by variational effective refractive index method. The dispersion characteristics are modified by vector wave equation considering the polarization of TE and TM modes. For Mach-Zehnder (M-Z) interferometer constructed by rib waveguide, the propagation characteristics of TM mode are analyzed by finite difference beam propagation method (FD-BPM). Moreover, operator expansion beam propagation method (OE-BPM) is applied to investigate M-Z interferometer waveguide in detail with fast speed. Based on the work above-mentioned, the structure parameters of M-Z interferometer are designed and optimized for the EO modulator operating in single mode.3. The propagation characteristics of microstrip line and coplanar line are studied, and the relationship between characteristic impedances and structure parameters is analyzed. After the simulation of the broadband transition from microstrip line to coplanar line, the specific structure parameters of high speed travelling wave electrode satisfying requirements are obtained. Meanwhile, a novel transition from microstrip line to coplanar line with slope is proposed to realize broadband transition. The simulation indicates that the performances of the electrode have been enhanced dramatically.4. The operation principle of organic/polymer M-Z OE modulator is discussed by its physical model, and the interaction between microwave and optical wave is investigated in detail. In the design of EO modulator, the performances have been analyzed and compared among rib waveguides and electrodes of different structure parameters to optimize the device.5. The fabrication processes and procedures of organic/polymer EO modulator are investigated by amounts of experiments. The low loss optical rib waveguide is fabricated by spin-coating, photolithography and reactive ion eatching. The thick Au electrode is fabricated by sputtering (evaporation), corrosion and electroplate. Careful research work has been conducted for poling process and stability to acquire as large as possible EO coefficient.In conclusion, the object of this thesis is the investigation of EO organic/polymer optical waveguide modulator. The main research work includes:1) A novel EO polymer material FFC/PSU is synthesized and characterized, the EO coefficient of which is 130pm/V; 2) Single parameter variational effective refractive index method with polarization modification is proposed to analyze the optical distributions and dispersion characteristics of optical rib waveguide, and the OE-BPM has been accelerated to shorten the computation time greatly; 3) A novel broadband slope transition from microstrip line to coplanar line is proposed to improve the propagation property of electrode, which enhances the modulation band of EO modulator obviously; 4) Based on the theoretical results above-mentioned, EO organic/polymer modulator and arrayed modulator are fabricated and measured to verify the validity and rationality of theoretical results.更多还原