石墨烯复折射率和电导率测量方法设计与研究

发布时间：2018-09-02 05:45

【摘要】：石墨烯作为一种二维材料,已经被广泛应用于光电器件的制作。复折射率和电导率是反映其电学特性和光学特性的两个重要参数。传统测量复折射率的方法如椭偏法具有测量仪器昂贵复杂和光学建模难度大的缺点,同时测量过程中没有引入光波导,测量结果对石墨烯光电器件的设计参考价值不大。传统测量石墨烯电导率的方法需要在其表面蒸镀金属电极,工艺难度大,且引入了接触电阻。因此,设计一种石墨烯混合光波导结构的测量石墨烯复折射率和电导率对于石墨烯光电器件的研究具有重要的意义。本论文基于上述研究背景,提出了一种石墨烯-长周期光纤光栅混合波导的结构用于测量石墨烯复折射率和电导率,重点研究了这一混合波导的测量理论和制备实验,主要完成以下工作:首先,本文对石墨烯基本光电特性和长周期光纤光栅的理论进行了阐述。针对石墨烯复折射率电导率的关系进行了探讨,分析了其可调控性。根据耦合模理论分析了长周期光纤光栅的透射率,且对其透射谱进行仿真,为后文石墨烯-长周期光纤光栅混合波导的建模奠定了理论基础。其次,本文根据两种方法建立了混合波导模型的包层模本征方程。对于第一种石墨烯复折射率包层模型,本文通过求解其本征方程,分析了石墨烯折射率实部和虚部对求解结果的影响,研究了石墨烯折射率实部和虚部对长周期光纤光栅谐振波长的影响。对于第二种表面电流模型,从电场的矢量模型出发,推导了其包层模本征方程,利用图解法研究了其求解结果。然后,本文对长周期光纤光栅的制作和石墨烯的制备进行了研究,利用拉曼光谱对石墨烯进行了表征,完成了石墨烯到长周期光纤光栅的转移实验,为后续测量混合波导传输特性的实验研究奠定了基础。最后,对石墨烯-长周期光纤光栅混合波导的透射谱展开实验测量,对比之前的理论模型,计算了石墨烯的复折射率和电导率,分析了测量误差。这一复合波导的结构增强了长周期光纤光栅对外界环境变化的灵敏度。因此,这一结构也可以实现对外界环境,如液体折射率等的高灵敏传感。
[Abstract]:As a two-dimensional material, graphene has been widely used in the fabrication of optoelectronic devices. The complex refractive index and conductivity are two important parameters reflecting their electrical and optical properties. The traditional methods of measuring complex refractive index, such as ellipsometry, have the disadvantages of expensive and complicated measuring instruments and difficult optical modeling. At the same time, optical waveguides are not introduced in the measurement process, so the results are of little reference value to the design of graphene optoelectronic devices. The traditional method of measuring the conductivity of graphene requires evaporation of metal electrode on its surface, which is very difficult, and the contact resistance is introduced. Therefore, the design of a graphene mixed optical waveguide structure to measure the graphene complex refractive index and conductivity is of great significance for the study of graphene optoelectronic devices. Based on the above research background, a structure of graphene / long period fiber grating hybrid waveguide is proposed to measure the complex refractive index and conductivity of graphene. The main work is as follows: firstly, the basic photoelectric properties of graphene and the theory of long period fiber grating are described. The relationship of complex refractive index conductivity of graphene was discussed and its controllability was analyzed. Based on the coupled mode theory, the transmittance of long-period fiber grating is analyzed, and its transmission spectrum is simulated, which lays a theoretical foundation for the modeling of graphene long-period fiber grating hybrid waveguide. Secondly, in this paper, the eigenequations of the cladding model of the mixed waveguide model are established according to two methods. For the first graphene complex refractive index cladding model, the effect of real and imaginary parts of graphene refractive index on the solution results is analyzed by solving its intrinsic equation. The effect of the real and imaginary parts of graphene refractive index on the resonant wavelength of long period fiber grating is studied. For the second surface current model, the eigenequation of the cladding model is derived from the vector model of the electric field, and the solution results are studied by using the graphical method. Then, the fabrication of long-period fiber gratings and the preparation of graphene were studied. The graphene was characterized by Raman spectroscopy, and the transfer experiment from graphene to long-period fiber grating was completed. It lays a foundation for the experimental study of the transmission characteristics of hybrid waveguides. Finally, the transmission spectrum of graphene / long-period fiber grating hybrid waveguide is measured experimentally. Compared with the previous theoretical model, the complex refractive index and conductivity of graphene are calculated, and the measurement errors are analyzed. The structure of the composite waveguide enhances the sensitivity of the long period fiber grating to the change of the external environment. Therefore, the structure can also achieve high sensitivity to the external environment, such as refractive index of liquid.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN253

【参考文献】