【作者】 刘坚强；

【导师】 王玲玲；

【作者基本信息】 湖南大学 ， 材料物理与化学， 2009， 博士

【摘要】 亚波长金属材料呈现出许多迷人的物理现象,在技术应用领域极具潜力,是当前凝聚态物理和近场光学研究的热点。在光与亚波长金属结构相互作用而引起的许多现象中,表面等激元起到了至关重要的作用。因此,对表面等离激元传播行为、规律及其操控手段的认识和探索,理论上将进一步加深和丰富人们对光与亚波长金属材料相互作用的认识,同时也将促进新一代微纳光子器件、全光回路的研究进展。本论文采用时域有限差分法(FDTD)针对亚波长金属结构中表面等离激元传播规律、行为的人工调控问题以及相关光学性质进行了比较系统的研究;在有效质量近似下对含结构缺陷半导体超晶格光学性质等问题进行了计算,获得的主要结果如下:通过改变相邻两波导的缝隙高度和在窄缝波导插入高折射率介质材料的方法,在理论上提出宽带隙等离子波导的设计原理。改变这种等离子波导的其中一层的宽度,在原来的光子禁带中出现了局域共振电磁模,并且这种电磁模局域在缺陷附近随着禁带宽度的加大而耦合减弱。提出在每个周期包含三个MIM波导的多禁带等离子波导结构对SPPs禁带的个数进一步进行调整,数值模拟计算证实这种三元金属波导结构可以形成多个光子禁带,在透射谱上的光子禁带之间的宽度可以通过改变其中相邻两层波导的宽度进行调节,为相关纳米光子器件设计提供了理论依据。研究了复合原胞周期性金属纳米方孔阵列的SPPs相位共振,发现复合金属纳米孔阵列的对称性破缺引起表面等离激元相位匹配条件被破坏,这使得在SPR共振透射带内特定的波长处透射率突然急剧降低形成SPPs相位共振。对于大小完全相同的复合周期方孔阵列,SPPs传播过程中的的相位差别主要依赖于孔阵列的对称性,当孔阵列的对称性发生改变时,透射谱的简并性随之发生变化。提出交替地填充两种不同的介质的方法实现对复合金属纳米孔阵列透射谱的调制。计算表明:当矩形孔的有效折射率差别较大时,孔的几何排列方式以及孔间距离并不能明显地改变矩形孔透射谱中由于局域表面等离子共振形成的透射峰;当矩形孔的有效率折射率差别较小时,复合矩形孔阵列的排列方式对透射谱有一定的影响。只有在局域共振峰与表面等离子共振峰重合时,孔间距离的改变只能在一定程度上改变透射谱的简并性。这些结果表明,通过改变孔内填充介质材料以及孔的排列方式通过改变矩形孔电磁模的耦合关系,有效调控LSP激发、耦合效率从而实现对透射谱的调节。这些研究结果为理解光与复合周期金属结构的相互作用提供了新的知识。探讨了结构缺陷和组分层厚度对含结构缺陷的半导体超晶格光跃迁几率的影响,分别计算了局域电子态-局域电子态之间和局域电子态-非局域扩展电子态之间电子在光照射下的跃迁几率。发现缺陷层厚度和与缺陷最近邻的组分层厚度对显著地改变这些电子态的跃迁几率,并且当改变这些层的厚度时局域电子态之间的跃迁几率对超晶格的微带微隙指数有明显的依赖作用,而局域态到非局域的扩展电子态之间的电子跃迁几率并不受微隙指数的影响。更多还原

【Abstract】 Subwavelength metallic materials are currently investigated intensively on manyfields including condensed matter physics and near fields optics, since they show intrigu-ing physics and potential application in many aspects. SPPs play a vital role in manyoptical phenomena on the subwavelenth dimensions, which make it enrich our knowl-edge about interactions between light and subwavelength metallic materials to study SPPspropagation behavior and related manipulation methods. At the same time, these investi-gations will promote the advance about the new generation of nanophotonic devices andall-optical circuits. By using the finite difference time domain (FDTD) method, this dis-sertation introduce a series of works on SPPs’s propagation law and some methods tomanipulate them, as well as related optical properties for subwavelength metallic mate-rials and structures. On the other hand, the modification of optical properties in semi-conductor superlattices with structure defects is discussed by using the effective massiveapproximation. The main results are summarized as follows:A wide bandgap plasmonic Bragg re?ector was proposed by changing the slit wide ofmetal-insulator-metal (MIM) waveguide and inserting dielectrics with high index. Whenchanging one of the thickness, the defect were introduced for this periodic structures, theresonant electromagnetic mode appear in the photonic band gap (PBG). Moreover, wefound this localized mode coupled poorer with the enlargement of PBG. Furthermore,the multiple PBG plasmonic Bragg re?ector was suggested, where three MIM waveguidewere included into every cell. Our numerical calculation verified SPPs can form morephotonic band gaps in this structures. Also, the width of PBG can be modified by changingthe slit width of MIM waveguide, which may be helpful to design the related nanophotoicdevices.SPPs phase resonance on the compound subwavelength hole arrays were investi-gated. It is found that phase match condition is broken when the symmetry of complexunit cell is destroyed, resulting in the transmission decrease suddenly at certain wave-length, namely the SPPs phase resonance. For the compound subwavelength hole arrayscomposed of identical square holes, the phase difference for SPPs are mainly governed bythe symmetry of complex unit cell, which leads to the degeneracy of transmission spectravary with the geometrical arrangement of this compound subwavelength hole arrays.A method was proposed that the transmission spectra of compound subwavelength arrays of rectangular hole can be modified by the filled dielectric alternately in a com-pound unit cell. The simulated results exhibit that the transmission for compound holearrays of rectangular holes with grater contrast of effective refractive, can not be affectedremarkably by the arrangement style or the symmetry of complex unit cell. However, thetransmission spectra may be modified at some extent by the interspace between holes forthe rectangular holes with low contrast of effective refractive. Only when the transmis-sion peak corresponding to LSP combines with SPPs resonance together, the variation ofsymmetry for complex unit cell makes its degeneracy be modified. These results showthat the transmission for compound arrays of rectangular holes can be manipulated bythe filled dielectric within the holes and/or the arrangement of compound unit cell, whichchanges the cutoff wavelength, leading to the variation of the excitation efficiency of LSPand its coupling behavior. These studies provide new knowledge about the interactionsbetween light and compound periodic metallic nanostructures.The effects of defect layers and constituent layers thickness on optical transition insemiconductor superlattice with structural defect were demonstrated, including transitionfrom localized electronics states to other localized electronic states, delocalized scatteringelectronic states. Our calculation displayed these transition probabilities are sensitiveto the defect layers and the nearest constituent layer thickness. Moreover, when theselayers thickness are altered, the variation tendency for transition probabilities between twolocalized states are governed by the parity of minband gap index n. However, transitionprobabilities between localized states and delocalized transition are not related to n.更多还原