基于太赫兹表面等离激元的偏振复用器件

发布时间：2018-01-07 19:29

本文关键词：基于太赫兹表面等离激元的偏振复用器件　出处：《哈尔滨工业大学》2016年博士论文　论文类型：学位论文

【摘要】：表面等离激元是局域在金属/电介质分界面传播的电磁振荡,具有亚波长、场局域和场增强的特性,在微纳集成光学、高灵敏传感、超分辨光刻与成像和提高太阳能电池效率等领域具有重要的应用前景。当光波入射到亚波长金属结构时,会激发表面等离激元,设计结构可调控表面等离激元的振幅和相位,实现不同功能(聚焦、涡旋、反射和产生特殊光束等)的表面等离激元器件。偏振作为光波的基本特性之一,在增加通信容量、3D显示和生物分子光谱与传感等领域有重要的应用。然而,传统的光电探测器和人的眼睛对光波偏振的响应并不敏感,这极大地限制了对于光波偏振的进一步应用。本论文利用表面等离激元的振幅和相位与入射光偏振密切相关这一特性,在太赫兹波段研究和设计了三种不同的偏振复用器件:半圆环太赫兹表面等离激元透镜、基于金属狭缝阵列的太赫兹表面等离激元透镜和偏振复用超表面透镜。线偏振太赫兹、左旋圆偏振太赫兹和右旋圆偏振太赫兹入射时,不同器件可分别在二维平面内或三维自由空间得到不同的聚焦场分布。设计的基于亚波长金属狭缝结构的偏振复用器件具有小型化和易集成的特点,可应用于圆偏振光的检测、偏振复用的信息传递和处理以及生物分子光谱与传感等领域,实际应用中可根据需要选择不同的器件,并调整器件参数。而且本文器件的设计原理可推广到其他波段(可见光、红外和毫米波等),只需对器件结构参数进行缩放。具体的研究工作内容包括:搭建了太赫兹表面等离激元成像系统,能够实现快速的大面积的太赫兹表面等离激元探测。该系统基于点扫描太赫兹表面等离激元探测系统与太赫兹全息成像系统,对探测光进行扩束,并进一步将双眼探头替换为CCD相机进行成像探测。而且,该系统可以同时测量太赫兹表面等离激元的振幅和相位,能够有效地弥补可见光波段表面等离激元探测技术很难探测相位的不足。利用该系统探测水平线偏振太赫兹入射到半圆环狭缝激发的太赫兹表面等离激元,得到的振幅图像清晰地揭示了太赫兹表面等离激元的聚焦过程,而从相位图像则可以看出聚焦过程中的古依相移。不同频率太赫兹表面等离激元的聚焦特性也进行了比较分析。该系统可以全面迅速的表征太赫兹表面等离激元器件,有助于器件的设计和加深对器件原理的理解。实验测量了半圆环太赫兹表面等离激元透镜的偏振复用聚焦,实验测量结果表明,当左旋圆偏振和右旋圆偏振太赫兹入射时,激发的太赫兹表面等离激元的焦点会分别发生方向相反的横向移动,但焦点横向移动的距离较小,小于入射太赫兹波长。测量得到的相位分布则清晰揭示了导致焦点横移的螺旋相位,为相关理论解释提供了坚实的实验基础。而且,不同于之前基于科里奥利效应和自旋霍尔效应的研究分析,该研究从太赫兹表面等离激元的惠更斯菲涅尔原理出发,结合傅里叶变换相关理论,得到了焦点偏移距离估算公式,并指出了公式的适用范围,分析更加清晰全面。设计了基于金属狭缝阵列的太赫兹表面等离激元透镜,在二维平面内,左旋与右旋圆偏振太赫兹入射时,激发的太赫兹表面等离激元焦点的分离距离为入射太赫兹波长的数十倍。首先理论上分析了利用金属狭缝阵列实现偏振控制太赫兹表面等离激元的激发,并进行了数值模拟。模拟结果表明,左旋圆偏振太赫兹入射时,激发的太赫兹表面等离激元向左传输,而右旋圆偏振激发的太赫兹表面等离激元向右传输。进而利用模拟退火算法对狭缝阵列的排布进行了重新优化,实现偏振复用聚焦。利用数值模拟和实验测量研究设计透镜的聚焦特性,结果表明,左旋圆偏振和右旋圆偏振太赫兹激发的太赫兹表面等离激元分别在透镜左侧和右侧聚焦,焦点之间的距离为入射太赫兹波长数十倍,而线偏振太赫兹入射则在器件左右两侧得到两个焦点。设计了基于超表面的偏振复用透镜,实现了三维自由空间的偏振复用聚焦和偏振复用成像。研究了在左旋圆偏振和右旋圆偏振太赫兹入射下,单个矩形狭缝天线的辐射场的振幅和相位特性。利用空分复用原理设计矩形狭缝天线的分布,实现偏振复用聚焦。模拟与实验结果表明,当左旋圆偏振太赫兹入射时得到的焦点在焦平面左侧,右旋圆偏振太赫兹得到的焦点在焦平面右侧,线偏振太赫兹入射则得到两个焦点,两焦点之间的距离数倍于入射太赫兹波长。两焦点之间的分离距离可根据需要调整。同时,设计的透镜还可实现偏振复用成像,可应用于偏振复用的信息传递和处理。
[Abstract]:The surface plasmon is localized on the metal / dielectric interface electromagnetic oscillation propagation, with the sub wavelength, local field and field enhancement properties in micro nano integrated optics, high sensitive sensor, super resolution imaging and lithography and improve the efficiency of solar cells and other fields has important application prospect. When light incident to sub wavelength the metal structure, will excite surface plasmon, surface plasmon tunable structure design of amplitude and phase excitation, to achieve different functions (focus, vortex, reflection and special beam etc.) the surface plasmon polarization components. As one of the basic properties of light, increasing the communication capacity, 3D display biological and molecular spectra and sensing fields have important applications. However, the response is not sensitive to the traditional photoelectric detector and the eyes of polarization, which greatly limits the optical polarization for further application of this theory. Paper with surface plasmon amplitude and phase and polarization of the incident light is closely related to the characteristics of terahertz wave in the research and design of three kinds of different polarization multiplexing devices: semi-circular terahertz surface plasmon lens, metallic slit arrays of terahertz surface plasmon polarization multiplexing ultra lens and lens based on surface linear polarization. Terahertz, terahertz polarization and right circularly polarized THz incident, different devices can be obtained from different focusing field distribution in 2D plane or 3D free space. The design of polarization multiplexing device of subwavelength metal slit structure based on miniaturization and easy integration characteristics, can be used in the detection of circular polarized light., polarization multiplexing of information transmission and information processing as well as the molecular spectrum and sensing fields, select a different device according to the need of practical application, and adjust the device parameters In this paper, the design principle and device can be popularized to other bands (visible light, infrared and millimeter wave), only need to zoom in and out of the device structure parameters. The specific work includes: build a polariton imaging system from terahertz surface, can realize the large fast product of terahertz surface plasmon detection. The system excitation detection system and THz holographic imaging system from scanning terahertz surface based on probe beam expander, and further will replace CCD camera imaging detection probe eyes. Moreover, the system can from the amplitude and phase measurement of terahertz surface plasmon at the same time, can effectively make up the visible band of surface plasmon polaritons defects detection technology very difficult to detect the phase detection. The horizontal line polarization incident to the semicircular ring slit excited terahertz using the system of terahertz surface plasmons, too The amplitude image clearly reveals the terahertz surface plasmon polaritons focusing process, and it can be seen from the phase image focusing process in Gouy phase shift. Different frequency terahertz surface plasmon polaritons focusing properties were also analyzed. The system can complete rapid characterization of terahertz surface plasmon components. Is helpful to design and deepen the understanding of the principle of the device. The device measured semi-circular terahertz surface plasmon and polarization multiplexing focusing lens, the experiment result shows that when the left circularly polarized and right circularly polarized incident terahertz, terahertz excitation of surface plasmon polaritons will focus the direction of the lateral movement occurs on the contrary, but the focus of the lateral movement distance is smaller and smaller than the wavelength of the incident THz. The phase distribution of the measured result is clearly reveals the spiral phase shifting focus, phase Provide a solid experimental basis theory explained. And, unlike previous research on the Coriolis effect and spin based on Holzer effect analysis, the study from terahertz surface plasmon polaritons Huygens Faye Nel principle of combining Fourier transform theory, the formula for estimating the focus offset distance, and points out the scope of the formula, analysis more clear and comprehensive. The design of metallic slit arrays of terahertz surface plasmon in the lens based on a two-dimensional plane, left - and right circularly polarized incident terahertz, terahertz excitation separation distance surface plasmon focus for several times. The first incident terahertz wavelength is analyzed to realize the polarization control of terahertz surface etc. from the excited element by using metallic slit arrays, and simulated. The simulation results show that the left circularly polarized THz incident excitation The terahertz surface plasmon transmission to the left, and right circularly polarized excitation of terahertz surface plasmon transmission. Then use the right configuration of the slit array is optimized and simulated annealing algorithm, realize polarization multiplexing focus. By focusing properties, numerical simulation and experimental study on measurement of lens design results show that the circularly polarized light and right circularly polarized THz excited terahertz surface plasmon respectively in the left and right focusing lens, focal distance between the incident wavelength of terahertz dozens of times, while the linear polarization incident in terahertz devices on both sides of two focus. Design of polarization multiplexing lens surface based on super, realizes the focusing and polarization multiplexing polarization multiplexing imaging 3D free space. On the left circularly polarized and right circularly polarized incident terahertz radiation field, a single rectangular slot antenna The amplitude and phase distribution characteristics. Using spatial multiplexing principle design of rectangular slot antenna, realize polarization multiplexing focus. Simulation and experimental results show that when the left circularly polarized THz incident focus on the focal plane of the left and right circularly polarized terahertz focus in the focal plane of the right line, get two THz polarization incident the focus of the two focus distance between several times in the incident terahertz wavelength. The separation distance between the two focus can be adjusted according to the requirement. At the same time, the design of the lens can realize polarization multiplexed imaging, information transmission and information processing can be used in polarization multiplexing.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O441.4

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