周期排列的电介质小球所诱发的金属-电介质表面上的表面等离子激元的光学性质

研究了金属板的上下表面附近各放置一层按周期排列的电介质小球的体系的光学性质.用多重散射法计算的结果显示金属上侧的周期性排列的电介质小球可诱发金属-电介质表面上的表面等离子激元.这些表面等离子激元的存在可通过非常尖锐的吸收峰反映出来.对于无限厚的金属板，这些吸收峰的峰值位置主要与电介质小球的周期有关，且与解析理论符合得相当好.在有限厚度的金属板中，金属板的两侧表面会产生对称和反对称的两种表面等离子激元，从而使原来在无限厚的金属表面上所出现的单一频率的表面等离子激元劈裂为双频率.由于对称和反对称的表面等离子激元模式在金属板的两侧表面均有相当强的电磁场，因而它们可导致强的电磁波穿透.通过在金属板的下侧加入玻璃球层可将表面等离子激元的电磁场引导出金属，并产生透射波.用多重散射法计算的结果证实，在此体系中由表面等离子激元所引起的透射可达到相当的强度. 对该体系中的物理机理进行了详细分析，从而能够通过调节该体系中的一些参数来控制表面等离子激元出现的频率，使强吸收峰或强透射峰出现在所希望的频率上.关键词：表面等离子激元吸收谱透射

Optical properties of surface plasmons induced by the plan of a periodically arranged dielectric spheres on the metal slab

Optical properties of a system composed of a metal slab with two planes of periodically arranged dielectric spheres on the metal surface have been investigated.The results obtained from multiple scattering method show that the periodic dielectric spheres on the upper surface of the metal could induce surface plasmons on the metal-dielectric interface.For a very thick metal slab,the existence of the surface plasmons can be observed by corresponding peaks in absorption spectrum.The position of the absorption peak is mainly determined by the periodicity ofdielectric spheres,and is consistent with the analytic theory very well.For the limited thickness of metal slab,there exist two surface plasmon modes,corresponding to symmetric and antisymmetric modes,respectively,and the absorption peak that occurs in the thick metal slab splits into a double-peak strurcture.For a symmetric or antisymmetric surface plasmon,the magnitudes of the electric and magnetic fields are the same on both sides of the metal slab,thus these surface plasmons can results in a strong transmittance.The plane of periodically arranged dielectric spheres beneath the metal slab can lead the surface field out of the metal,and form a transmission plane wave.The results obtained from multiple scattering method show that the transmittance is fairly high when surface plasmons exist.The fundamental physical mechanism is studied in detail,and the occurrence of the surface plasmons,and hence the position of the peak of absorbance or transmittance,can be controlled by adjusting corresponding parameters in the system.