Nanophotonics and Metrology Laboratory, Swiss Federal Institute of Technology (EPFL) , CH-1015 Lausanne, Switzerland.
Nano Lett. 2017 Apr 12;17(4):2265-2272. doi: 10.1021/acs.nanolett.6b04906. Epub 2017 Mar 22.
Plasmonic antennas and planar structures have been undergoing intensive developments in order to control the scattering and absorption of light. One specific class, extrinsic chiral surfaces, that does not possess 2-fold rotational symmetry exhibits strong asymmetric transmission for different circular polarizations under obliquely incident illumination. In this work, we show that the design of those surfaces can be optimized with complex multipolar resonances in order to twist the fluorescence emission from nearby molecules. While this emission is usually dipolar and linearly polarized, the interaction with these resonances twists it into a multipolar radiation pattern with opposite helicity in different directions. The proposed structure maximizes this effect and provides control over the polarization of light. Splitting of left- and right-handed circularly polarized light is experimentally obtained in the backward direction. These results highlight the intricate interplay between the near-field absorption and the far-field scattering of a plasmonic nanostructure and are further used for modifying the emission of incoherent quantum sources. Our finding can potentially lead to the development of polarization- and angle-resolved ultracompact optical devices.
为了控制光的散射和吸收，等离子体天线和平面结构一直在进行深入的开发。一类特殊的外赋手性表面，不具有 2 重旋转对称性，在斜入射照明下，对于不同的圆偏振光表现出强烈的不对称透射。在这项工作中，我们表明，通过复杂的多极共振可以优化这些表面的设计，从而扭曲附近分子的荧光发射。虽然这种发射通常是偶极子和线性偏振的，但与这些共振的相互作用将其扭曲成具有相反螺旋的多极辐射模式，在不同方向上具有相反的螺旋。所提出的结构最大限度地提高了这种效果，并提供了对光偏振的控制。在向后方向上实验获得了左旋和右旋圆偏振光的分裂。这些结果突出了等离子体纳米结构近场吸收和远场散射之间的复杂相互作用，并进一步用于修饰非相干量子源的发射。我们的发现有可能导致发展出偏振和角度分辨的超紧凑光学器件。
