基于导模谐振的超高Q太赫兹超材料研究

发布时间：2018-01-29 03:56

本文关键词： 太赫兹超材料高Q 导模　出处：《中国计量大学》2016年硕士论文　论文类型：学位论文

【摘要】：超材料(Metamaterial)是一类由亚波长结构周期性排列的人工复合材料,由于其特殊的电磁效应,因而受到广泛关注,这些特殊的电磁特性来自于超材料丰富的谐振效应。关于谐振峰的评价指标就是品质因子(Q值),但是由于受到辐射损耗和金属欧姆损耗的影响,谐振峰的Q值很难大幅度提高,传统的获得高Q值的方法都是基于超材料表面模式建立的,这些方法虽然能在一定程度上压制辐射损耗,但是效果却相当有限。由于超材料结构的周期性,可以将其等效为一种类光栅结构,电磁波入射时也会产生光栅衍射效应,此效应可将入射电磁波耦合进波导,激发导模谐振。这一类谐振是由于波导限制电磁波的传输而产生,可以极大地抑制能量向自由空间的辐射,实现谐振峰的超高Q值,这在光栅领域已经有相关报道证实。本文首次利用金属单闭环在超材料领域引入导模谐振,并研究了各结构参数对导模谐振的调控作用,进一步在此基础上提出了两种分别以金属双闭环和金属双开口环为例的调控超材料导模以获得高Q的方法:(1)基本结构单元为两个金属闭环均匀分布于X方向周期为2d、Y方向周期为d的PI薄膜上,此时超材料相邻两个金属环间中心距均为d,实际周期也为d,类似于一个均匀的二维光栅。有电磁波入射时,就会产生光栅衍射效应,并激发光栅周期为d的导模。当将两个金属闭环进行相向或反向平移(这二者是等价的)时,就会造成超材料相邻两个金属环间的中心距离不等,引入2d光栅周期并激发该周期的导模。通过调节平移量可以调控导模能量在2d光栅周期上的分量(即调制深度),从而调节此导模谐振峰的Q值和幅值。通过仿真研究,平移量越小,导模谐振峰的Q值越高而幅值越小,仿真中可达104以上。在此基础上继续讨论了波导层厚度对导模谐振峰的影响,研究发现波导层材料以选取损耗小厚度薄的为佳。最后,用激光直写化学镀铜方法加工了样品,并用THz-TDS进行了测试,实验结果与仿真结果高度吻合。(2)基本结构单元为两个金属开口环均匀分布于X方向周期为2d、Y方向周期为d的PI薄膜上,其中两个环的开口位置分别分布在环的上部和下部。当将两个金属环以各自环中心为圆心同时旋转或者将两个金属环的开口位置进行相向或反向平移时,这样也能引入2d的光栅周期并激发该周期的导模,与前一种方法的规律类似,旋转角度或平移量越小,导模谐振峰的Q值越高而幅值越小,仿真中同样获得了104以上的Q值。另外,还提出了一种调控基于导模与偶极谐振峰相互作用产生的类EIT谐振峰的峰宽调控方法,并在仿真中给出了调控的效果。最后,同样用激光直写化学镀铜方法加工了样品,并用THz-TDS进行了测试,实验结果与仿真结果高度吻合。
[Abstract]:Metamaterial) is a kind of artificial composite which is arranged periodically by subwavelength structure. Because of its special electromagnetic effect, it has been paid more and more attention. These special electromagnetic properties come from the rich resonance effect of metamaterials. The evaluation index of the resonance peak is the Q value of the quality factor, but it is affected by the radiation loss and the metal ohmic loss. The Q value of the resonant peak is difficult to increase greatly. The traditional methods of obtaining high Q value are based on the surface mode of metamaterials, although these methods can suppress the radiation loss to a certain extent. However, the effect is quite limited. Because of the periodicity of the supermaterial structure, it can be equivalent to a kind of grating structure, and the grating diffraction effect will also occur when the electromagnetic wave is incident, which can couple the incident electromagnetic wave into the waveguide. This type of resonance is caused by the waveguide limiting the transmission of electromagnetic waves, which can greatly suppress the energy radiation to the free space and achieve the high Q value of the resonance peak. This has been confirmed in the field of grating. In this paper, we first use metal single closed-loop to introduce the guided mode resonance in the field of supermaterials, and study the regulation of the structure parameters on the guided mode resonance. On the basis of this, two ways to obtain high Q are proposed, one is metal double closed loop and the other is metal double open ring. The basic structural elements are two metal close-loop uniformly distributed in the X-direction cycle of 2d. On Pi thin film with Y direction period d, the center distance between two adjacent metal rings is both d and the actual period is d, which is similar to a uniform two-dimensional grating. The grating diffraction effect is generated and the guided mode with a grating period of d is excited. When the two metal closed loops are shifted in opposite direction or in reverse direction (which are equivalent). The distance between the centers of the two metal rings adjacent to the metamaterials is not equal. The period of 2d grating is introduced and the guided mode of the period is excited. The component of guided mode energy (i.e. modulation depth) on the period of 2d grating can be adjusted by adjusting the translation. Through the simulation, the smaller the translation, the higher the Q value and the smaller the amplitude of the guided mode resonance peak. On the basis of this, the influence of waveguide thickness on the resonant peak of guided mode is discussed. It is found that the material of waveguide layer is better to select the thin one with small loss. Finally, the influence of the thickness of waveguide layer on the resonant peak of guided mode is discussed. The samples were fabricated by laser direct writing electroless copper plating and tested by THz-TDS. The experimental results are in good agreement with the simulation results.) the basic structural elements are two open metal rings uniformly distributed on Pi thin films with the X direction cycle of 2dU Y direction period of d. The opening positions of the two rings are distributed in the upper and lower parts of the ring respectively.; when the two metal rings are rotated at the center of each ring at the same time or the opening positions of the two metal rings are shifted in opposite direction or reverse. In this way, the grating period of 2d can be introduced and the guided mode of the period can be excited. Similar to the rule of the former method, the smaller the rotation angle or the translation, the higher the Q value and the smaller the amplitude of the resonant peak of the guided mode. The Q value above 104 is also obtained in the simulation. In addition, a method to adjust the width of the EIT resonant peak based on the interaction between the guide mode and the dipole resonant peak is proposed. The control effect is given in the simulation. Finally, the sample is processed by laser direct writing electroless copper plating method, and tested by THz-TDS. The experimental results are in good agreement with the simulation results.
【学位授予单位】：中国计量大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB33

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