磁单负材料板附近的原子的自发辐射场分布

Spontaneous emission field excited by an atom near the μ-negative metamaterials slab

本文研究了磁单负材料板附近的两能级原子通过自发辐射激发的表面模式及场强分布.磁单负材料是有效介电常数大于零而磁导率小于零的人工微结构材料.根据麦克斯韦方程及边界条件,这种材料板只支持TE极化的表面模式.本文分析了具有不同磁导率和厚度的磁单负材料板所支持的表面模的性质,如模式数目和模式的对称性,进而讨论了这些特性对原子自发辐射场的空间分布的影响.结果表明原子与磁单负材料板的距离可影响辐射场中表面模的比重,当表面模起主要贡献时,在材料板左表面上原子辐射场呈定向发射的分布.而材料板右表面的辐射场分布取决于表面模的对称性和比重,如果同时存在对称和反对称的表面模,右表面的场很弱甚至完全消失,而如果只存在对称或反对称的表面模,右表面会有与左表面等强度的辐射场分布.这些性质与原子在金属表面的辐射场分布明显不同,我们的结果对原子辐射场的空间控制以及实现简单结构的单光子源有积极意义.

This paper discusses the spontaneous emission field of a two-level atom near a μ-negative metamaterial（MNG） slab, in which the surface modes are excited, the μ-negative metamaterial is a kind of artificial-microstructured materials possessing effective negative permeability and positive permittivity. According to Maxwell＇s equations and boundary conditions, the MNG slab supports only TE-polarized surface modes.We analyze the properties of the surface mode, i.e.the number of the surface mode and its symmetry or antisymmetry profiles, supported by the MNG slab with different permeability and thickness, and then study the influence of these characteristics on the spatial distribution of the spontaneous emission field in detail. Results show that the distance between the atom and the slab can affect the ratio of surface mode to the total atomic emission field. When the surface mode plays the dominate role, the spontaneous emission field of the atom on the nearest surface of MNG slab are directionally propagating along y-axis if the atomic dipole is along x-axis due to the TE-polarized surface mode. The atomic emission field on the other surface depends on the symmetry of the surface modes and their percentage. If the symmetric and antisymmetric surface modes coexist, the field intensity on the right surface is weakened or even disappears completely, but if there exists only symmetric or antisymmetric surface mode, the field intensity on the right surface is nearly identical with that on the left surface. These phenomena are significantly different from the case of atoms near a metal slab or a dielectric slab. Our results are useful for the controllable atomic emission and have potential application to the single-photon source.