【作者】 李胜；

【导师】 张怀武；

【作者基本信息】 电子科技大学 ， 电子信息材料与元器件， 2010， 博士

【摘要】 太赫兹(THz)频谱代表一个特别有趣的频段,它既不能很明确地归于微波段或光波段,又不能用目前已有的微波或者光波理论去直接研究。但其有着广泛的应用前景,因此THz产生、接收、与物质的作用及其传输等相关领域成为目前国际上的研究热点和难点。由于缺少低损耗、低吸收、低色散传输THz波的波导材料,现有的THz波系统都是基于自由空间传播理论,而太赫兹波在自由空间中的传输损耗又很大,因此,以波导为基础的太赫兹材料和器件就成了太赫兹传输的重要基础,也是太赫兹波能否广泛应用的关键。光子晶体和电磁超颖材料作为一种新型人工材料有望在THz功能器件的开发和研制中起到越来越大的作用,也成为THz系统的集成化和小型化的研究热点。本论文主要围绕光子晶体和电磁超颖材料在THz频段的应用基础而展开,论文的主要内容包括:1.THz光子晶体功率分配器:利用平面波展开法理论,通过改变二维正方形THz光子晶体的结构对其带隙进行优化,在此基础上设计不同结构的二维正方形THz光子晶体功率分配器,并利用时域有限差分法对进行分析比较,结果发现改进型T形功率分配器通带幅频特性的平坦度为84%和92%,优于普通型T形功率分配器的频带平坦度76%,另外改进型T形功率分配器的两输出端口间的隔离度也高于普通型。改进型Y形功率分配器-3dB带宽达0.224THz,峰值为1655.73,都优于普通型的0.216 THz和1577.25,使改进型的Y形功率分配器更为实用。在以上理论分析的基础上,我们利用现代光刻工艺制备了相应的二维THz光子晶体功率分配器。2. THz光子晶体上/下载滤波器:设计了不同结构的二维正方形THz光子晶体上/下载滤波器并利用时域有限差分法对其进行分析比较,研究结果表明,三个点缺陷组成的L形谐振腔结构的上/下载滤波器可以同时上/下载三个频率点,四个点缺陷组成的右T形上/下载滤波器的峰间频率间隔达0.342 THz,可以实现较大频率间隔的双频点上/下载滤波。在以上理论分析的基础上,我们利用现代光刻工艺制备了相应的二维THz光子晶体上/下载滤波器,并已取得部分测试结果。3. THz光子晶体窄带滤波器:设计了不同结构的二维正方形THz光子晶体窄带滤波器并利用时域有限差分法对其进行研究,发现垂直于输入输出波导的三缺陷窄带滤波器可以同时对两个频率进行幅度接近100%的滤波,而且其带外抑制特性优良,该结构可利用于双频点的高Q值窄带滤波。由五个单缺陷形成的左向长T形结构的窄带滤波器有五个透射峰,其独特的幅频特性也可以利用。4.THz电磁超颖材料功能器件方面。利用现代光刻技术工艺制备了一种圆形和两种分别在X和Y方向伸展的椭圆形裂环谐振器,并在太赫兹时域系统进行测试,比较了尺寸结构参数和耦合系数对幅频特性的影响。根据测试结果提出包含LC谐振、偶极子谐振和第三种谐振模式的改进型TL-RLC理论模型使模型与实验数据更为吻合。另外研究了谐振臂和谐振缝隙同时旋转时角度改变对LC谐振和偶极子谐振之间的频率间隔产生的影响,提出扩展LC谐振和偶极子谐振之间的频率间隔的新方法。旋转角度为0.02°到0.24°或者-0.02°到-0.24°时,频率间隔的绝对增加值为25.2GHz,相对增加值为2.62%。当旋转角度为0.2°时的S参数与未旋转时的S参数差别很小,而且在S曲线上可以看出没有引入其他的谐振峰。还以包含LC谐振、偶极子谐振和第三种谐振模式的改进型TL-RLC理论模型为出发点,研究了第三种谐振模式,并推出其谐振频率表达式。更多还原

【Abstract】 The terahertz (THz) spectrum (0.1–10 THz, 1 THz =1012Hz) represents a particularly interesting region. Terahertz frequencies cannot clearly be attributed to be either on the "electronic" side or on the "optics" side. The THz frequency radiation has been proven to be a fertile region in the electromagnetic spectrum and a powerful tool in scientific research and many applications. THz waves has significant transmission loss in free space, so waveguide-based terahertz devices have become very important foundation for the THz transmission, also the key to the wider use. Although enormous efforts have focused on the search for terahertz materials or alternative novel techniques to enable the construction of device components, much work remains. Photonic crystals (PCs) and metamaterials as a novel artificial material would play a more and more important role in the development of THz functional device and contribute to THz systems integration and miniaturization. The main contents are summarized as follows:1. Based on plane wave expansion method, the band gaps of two-dimensional (2D) THz PCs with typical square structures are optimized by changing structural parameters. The electromagnetic field distribution of THz waves in 2D photonic crystals functional device had been simulated through the finite difference time domain method. The improved T-splitter has better amplitude-frequency characteristics in pass-band and better separation degree between the two output ports than the common T-splitter. The improved Y-splitter excels to the common Y-splitter in the amplitude and -3dB bandwidth. The 2D THz splitter PCs components had been fabricated by modern micro-fabrication processes.2. Introducing the photonic band gap structure with L-type defects composed of three defects, three high-Q resonant frequencies had been simultaneously dropped (or added). The rightward T-type structure filter can extend the interval between two dropping (or adding) frequencies to 0.342 THz. The upload (or download) PCs filter had been fabricated.3. The cavity with three defect, perpendicular to the three-defect input and output waveguide, can simultaneously select two frequencies about 100% amplitude, and can be used in the dual-points or dual-band high-Q narrow-band filter. The leftward T-shaped structure formed by five single-defects has five transmission peaks. The amplitude-frequency property can be used in high-Q narrow-band filter.4. Three geometries of split ring resonators,a circular geometry and two elliptical geometries, are fabricated by a series of micro-fabrication processes for terahertz metamaterials. The samples are measured by the transmission spectroscopy in terahertz time domain. These transmission spectra had been compared for the change effect of the structure parameters and coupling coefficient on the amplitude-frequency characteristics. An improved Transmission-line RLC circuit model is used to help us understand this coupling behavior and the extent of its effects. The gap and gap-bearings are simultaneously in-plane rotated for widening the metamaterials separation between the inductive-capacitive (LC) and dipole resonances. According to improved TL-RLC model, another kind of resonant modes is studied by simulation software, and derived its expression of resonant frequency.更多还原