Department of Physics, King's College London, Strand, London WC2R 2LS, UK.
Science. 2013 Apr 19;340(6130):328-30. doi: 10.1126/science.1233739.
Wave interference is a fundamental manifestation of the superposition principle with numerous applications. Although in conventional optics, interference occurs between waves undergoing different phase advances during propagation, we show that the vectorial structure of the near field of an emitter is essential for controlling its radiation as it interferes with itself on interaction with a mediating object. We demonstrate that the near-field interference of a circularly polarized dipole results in the unidirectional excitation of guided electromagnetic modes in the near field, with no preferred far-field radiation direction. By mimicking the dipole with a single illuminated slit in a gold film, we measured unidirectional surface-plasmon excitation in a spatially symmetric structure. The surface wave direction is switchable with the polarization.
波的干涉是叠加原理的一种基本表现形式，具有广泛的应用。虽然在传统光学中，干涉发生在传播过程中相位不同的波之间，但我们表明，发射器近场的矢量结构对于控制其辐射是至关重要的，因为它在与中介物体相互作用时会与自身干涉。我们证明，圆偏振偶极子的近场干涉会导致引导电磁模式在近场中单向激发，而没有优先的远场辐射方向。通过用金膜中的单个照亮狭缝来模拟偶极子，我们在空间对称结构中测量到了单向表面等离子体激发。表面波的方向可以通过偏振来切换。
