压力场中锗光学性质的第一性原理计算与实验分析

发布时间：2018-04-10 16:28

本文选题：第一性原理计算 + 半导体　；参考：《武汉理工大学》2015年硕士论文

【摘要】：锗折射率在压力下的变化是其他常见的半导体的4~6倍,作为良好的压敏材料,可以将其应用在光纤传感中。但是在入射光波长小于1850nm的吸收区内锗折射率的实验数据及折射率随压力的变化情况未知。论文使用第一性原理计算软件的CASTEP模块,建立了锗晶体的3D模型并进行几何优化;计算了锗的能带结构,并以此为基础推导出介电函数、吸收系数和折射率等光学常数,对计算的结果进行了误差分析。接着运用软件设置环境压力,理论研究了当外界压力变化时,锗折射率的相应变化,得出了锗折射率随压力变化的定量关系。在理论计算过程中,详细分析并给出了相关参数的设置,讨论了Properties处K点数对最终计算结果准确性的影响,最终确定此处K点数设置为11*11*11。为了获得锗折射率-压力关系的实验数据,论文设计并定制了可用于光纤探针的特种液压机。该液压机以液压油为介质,能够实现在0~25MPa区间内连续施加或卸载压力。用于测试的压力传感器,在光纤端面上蒸镀一层纳米量级的半导体锗作为敏感探头,构成一种新型的光纤半导体压力传感器。当液压机压力发生变化时,光纤端面处锗的折射率也会发生相应的变化。通过检测端面的反射率便可建立反射率与外界压力的对应关系,进而推导得到折射率-压力的传感模型。实验结果表明,光纤端面所镀锗薄膜的厚度会对最终检测结果产生很大的影响。论文通过第一性原理计算得到了锗的光学常数及其随外界压力变化的定量关系;并通过实验获得了锗折射率-压力关系的实验数据。通过对理论计算和实验测量结果的分析得出锗折射率随着外界压力的增加而线性减小的结论,论文工作首次为压力场中半导体光学参数的研究提供了实验数据参考。
[Abstract]:The change of GE refractive index at pressure is 4 ~ 6 times of that of other common semiconductors. As a good varistor, germanium can be used in optical fiber sensing.However, the experimental data of germanium refractive index and the change of refractive index with pressure in the absorption region with incident wavelength less than 1850nm are unknown.In this paper, the 3D model of germanium crystal is established and optimized by using the CASTEP module of first-principle calculation software, the energy band structure of germanium is calculated, and the optical constants such as dielectric function, absorption coefficient and refractive index are derived.The error analysis of the calculated results is carried out.Then the corresponding change of germanium refractive index when the external pressure changes is studied theoretically by using the software to set the environmental pressure. The quantitative relationship between the germanium refractive index and the pressure change is obtained.In the course of theoretical calculation, the setting of relevant parameters is analyzed and given in detail, and the influence of K points at Properties on the accuracy of final calculation results is discussed.In order to obtain the experimental data of the relationship between refractive index and pressure of germanium, a special hydraulic press which can be used in optical fiber probe is designed and customized in this paper.With hydraulic oil as the medium, the hydraulic press can continuously apply or unload pressure in the 0~25MPa region.A new type of optical fiber semiconductor pressure sensor is formed by vaporizing a layer of nanocrystalline germanium on the optical fiber end surface as a sensitive probe.When the pressure of hydraulic press changes, the refractive index of germanium at the end of the fiber will also change.The relationship between reflectivity and external pressure can be established by measuring the reflectivity of the end face, and the sensing model of refractive index and pressure can be derived.The experimental results show that the thickness of GE film on the end surface of the fiber has a great influence on the final measurement results.In this paper, the optical constants of germanium and its quantitative relationship with external pressure are calculated by first principles, and the experimental data of the refractive index pressure relationship of germanium are obtained.The conclusion that the refractive index of germanium decreases linearly with the increase of external pressure is obtained by analyzing the theoretical calculation and experimental measurement results. The work of this paper provides the experimental data for the study of semiconductor optical parameters in the pressure field for the first time.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN304.11

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