【作者】 梁东；

【导师】 邢岐荣；

【作者基本信息】 天津大学 ， 光电子技术， 2007， 硕士

【摘要】 随着THz产生和探测技术的发展,设计和制作THz波段的传输和控制器件变得越来越迫切。本文提出了THz波段的很有潜力的候选传输器件——THz波段微结构金属光栅,并对其性质进行了创新性的理论和实验研究。本文先从基本电磁理论出发,应用弗洛奎—布洛赫定理和表面波阻抗匹配边界条件,在电磁波以p偏振态入射的情况下,将麦克斯韦方程用于求解微结构金属光栅各个空间场分布的解析表达式。进一步将微结构金属光栅等效成F-P标准具,并求出了光栅上下表面的透射和反射系数。在近周期波段(入射波长与光栅周期相近)和长波段(入射波长远大于光栅周期)分别分析了金属光栅的性质。在近周期波段,光栅表现出著名的Wood反常现象。在长波段,从理论上论证了亚波长金属光栅可以等效为具有均匀等效折射率的奇异介质(Metamaterials)平板,并且在其表面支持类表面等离激元极化波(SPPs),这种被束缚的表面波使得亚波长光栅表现出了增强的透射效应。另外,本文还首次从理论上论证了周期不变、缝宽啁啾变化的亚波长微结构金属光栅具有自聚焦效应。实验上,我们利用基于ZnTe的THz时域光谱系统考察了自己制作的微结构金属光栅在p偏振THz波垂直入射时的一次非共振透射特性。测得的透射曲线与理论上按照正态分布的非均匀光栅周期所对应的透过率相符。同时,我们还测量了当光栅样品绕THz波入射方向旋转时的透射率,理论上从电场矢量投影关系结合晶体的偏振相关探测特性成功解释了所得到的透射现象。更多还原

【Abstract】 With the development of generation and detection of Terahertz radiation, the design and fabrication of the controlling device in THz frequency region become more and more imperative. In the thesis, a candidate device for controlling THz radiation is proposed, which is microstructured metallic grating in THz frequency region. A theoretical and experimental study on the proposed metallic grating is detailed.Based on the fundamental electromagnetic theory, we obtain the field distribution in whole space by applying Floquet-Bloch Theorem and surface impedance boundary condition to the metallic grating exposed to p-polarized electromagnetic wave. Furthermore, we treat the microstructured grating as effective F-P interferometer, then extract the scattering coefficients of both the front and bottom surface of the grating. When the incident wavelength is close to the grating period, the grating exhibits famous Wood anomalies. When the incident wavelength is larger than the grating period, it is demonstrated theoretically that the grating can be considered as a kind of metamaterials with homogenous refractive index equal to the ratio of grating period to the slit width. The surface of such a microstructured grating can support the bond surface mode similar to the Surface Plasmon Polaritons(SPPs). It is shown that the grating exhibits enhanced transmission due to the surface mode. In addition, we have proposed theoretically in the long wavelength region that the microstructured metallic grating with constant period but chirped slit width behaves self-focusing effect.We have used ZnTe-based THz time domain spectroscopy(THz-TDS) to experimentally investigate the nonresonant transmission of the microstructured metallic grating perpendicularly impinged by p-polarized THz radiation pulse. The experimental results agree with the theoretical calculation under the assumption that the nonuniform period of the grating satisfying normal distribution. Meanwhile, the transmission is also measured when the grating is rotated around the axis perpendicular to the grating surface. We have successfully explained the transmission theoretically by employing electric field vector projection and polarization-dependant detection of the ZnTe crystal.更多还原