Hussain R, Keene D, Noginova N, Durach M
Opt Express. 2014 Apr 7;22(7):7744-55. doi: 10.1364/OE.22.007744.
Strong modification of spontaneous emission of Eu(3+) ions placed in close vicinity to thin and thick gold and silver films was clearly demonstrated in a microscope setup separately for electric and magnetic dipole transitions. We have shown that the magnetic transition was very sensitive to the thickness of the gold substrate and behaved distinctly different from the electric transition. The observations were described theoretically based on the dyadic Green's function approach for layered media and explained through modified image models for the near and far-field emissions. We established that there exists a "near-field event horizon", which demarcates the distance from the metal at which the dipole emission is taken up exclusively in the near field.
在显微镜装置中，分别针对电偶极跃迁和磁偶极跃迁，清晰地展示了置于薄金膜、厚金膜及银膜附近的铕（Eu(3+)）离子自发发射的强烈调制。我们已经表明，磁跃迁对金基底的厚度非常敏感，并且其行为与电跃迁明显不同。基于分层介质的并矢格林函数方法对这些观测结果进行了理论描述，并通过近场和远场发射的修正镜像模型进行了解释。我们确定存在一个“近场事件视界”，它划定了与金属的距离，在该距离处偶极发射仅在近场中被吸收。
