亚波长槽缝结构中超强透射机理及在光纤通信中的应用研究

【作者】 秦子健；

【导师】 李相银；

【作者基本信息】 南京理工大学 ， 光学工程， 2010， 硕士

【摘要】 自在亚波长金属小孔阵列中发现超强透射现象以来,人们对于这一现象的物理机制进行了广泛的研究并利用这一现象来设计光学器件。研究表明表面等离子体在超强透射现象中起到了至关重要的作用。本文基于以上的研究背景,从麦克斯韦方程出发,利用严格耦合波理论,分析了超强透射的物理机理,研究了槽缝结构,并设计出一种亚波长金属结构,此结构在常用的光纤通讯窗口(1550nm)处实现了光放大和光隔离的结合。本文的研究内容分为以下三个部分：1.由于目前超强透射现象的物理机制还不是很明确,目前国际上有三种公认程度较高的模型,分别是表面等离子体激元(SPP),复合衍射衰逝波(CDEW)和谐振腔(CM)模型。本文把亚波长金属结构简化为一个三层薄膜透射情况,利用导纳矩阵推导出近似情况下的透射率计算方式。利用严格耦合波理论分析了单层薄膜单狭缝结构中结构参数对透射率的影响,并把分析结果和推出的解析解进行比较,验证了近似情况下解析解的正确性,并利用提出的模型解释了结构参数对透射率的影响,为理解超强透射现象的物理机制提供了参考。2.超强透射现象正被不断地应用于光学集成器件的设计中,但目前实验和数值模拟研究较多的波段是为380nm-800nm,而目前在应用前景较广的光纤通信窗口研究较少。本文利用严格耦合波理论(RCWA),研究了单缝-凹槽结构参数对超强透射现象的影响,发现了两个现象：(1)透射率会随凹槽与狭缝的距离变化发生周期性变化,另外透射场振幅会随着凹槽与狭缝的距离变大而呈现下降趋势；(2)随凹槽数量不断增大,透射增强和削弱程度不断加大,当凹槽数量达到一定程度时(本文结构中凹槽数量n=4时)透射增强和削弱的程度会趋于稳定。3.通过研究单狭缝中结构参数对超强透射的影响,根据单狭缝结构中透射增强峰和削弱峰的位置,设计凹槽的位置,在1550nm处实现了在同一槽缝结构中光的放大和隔离两个功能。为了更好的实现光的放大和隔离效果,本文设计了周期性双缝结构,通过合理的参数选取,在1550nm处取得了更好的光放大和隔离的效果,由于1550nm这个通信窗口的特殊性,使得本文的设计结果对超强透射现象在光通信领域的应用有一定的参考意义。更多还原

【Abstract】 There has been wide range of research in the physical origin of Extraodinary Optical Transmission(EOT) and using it to design optical devices since EOT was reported when light wave goes through arrays of sub-wavelength apertures on a piece of metallic film. The study shows that the surface plasmons played a crucial role in the phenomenon of EOT.Based on the above research background, starting from Maxwell’s equations, the rigorous coupled-wave theory is adopted to analysis the physical origin of EOT.Through investigating the structure of groove-slit, design a subwavelength metal structure,when the light of 1550nm wavelength goes through the structure, the structure can achieve optical amplification in one direction, while the strucre can achieve optical isolation in another direction.The details are as follows:1. Currently the physical origin of EOT is not very clear, the current internationally accepted models of EOT are SPP, CDEW and CM models. By simplifying the structure of the metal film, the transfer matrix is used to calculate the transmission rate. We study the effects of structural parameters on the transmission rat by rigorous coupled-wave, and compare the simulation results with the analytical solutions, at the same time explain the simulation results using analytical solutions, the above research provides a reference for understanding the physical origin of EOT.2. The EOT has been widely used in the design of optics,but now most people focused on the wavelength between 380nm to 800nm,presently there is little research on optical fiber communication windows. We studied the effects of groove-slit’s structural parameters on the transmission rat by rigorous coupled-wave. (1) we find that transmission rate periodically varies with the distance between groove and slit,the amplitude will reduce as the the distance between groove and slit increases. (2) we also find that with the growing number of grooves, strengthening and weakening degree of transmission increase,but when the number reaches a certain amount (the number of grooves n = 4) the degree will stabilize.3. According to the research of the enhanced position and weakened position,we design the location of grooves and realize the amplification and isolation of light in 1550nm wavelength.In order to achieve better effect,we design a cyclical double-slit structure.As the communication window of 1550nm is unique, the design provides a reference for the application of EOT in the optical communication.更多还原