非手性高密度介电纳米粒子平面阵列中螺旋度密度最大化
Helicity Density Maximization in a Planar Array of Achiral High-Density Dielectric Nanoparticles
摘要：
我们研究了由非手性各向同性高折射率电介质纳米球组成的周期性阵列如何在阵列表面产生近场，达到非常接近其上限的螺旋密度。由阵列有效的电磁极化率导出了纳米球阵列产生最佳手征近场的条件，该条件代表了螺旋度密度的上界，几乎满足阵列的有效Kerker条件.所讨论的概念发现在改善手性检测的基础上，圆二色性（CD）在表面水平，而不是在散装的应用。重要的是，当用作用于检测手性分子薄层的手性的基底时，阵列不会对所产生的CD信号有贡献。这消除了将由阵列产生的CD信号与手性样品的CD信号分离的需要。
英文摘要：
We investigate how a periodic array composed of achiral isotropic high-refractive index dielectric nanospheres generates nearfield over the array surface reaching helicity density very close to its upper bound. The required condition for an array of nanospheres to generate optimally chiral nearfield, which represents the upper bound of helicity density, is derived in terms of array effective electric and magnetic polarizabilities that almost satisfy the effective Kerker condition for arrays. The discussed concepts find applications in improving chirality detection based on circular dichroism (CD) at surface level instead of in the bulk. Importantly the array would not contribute to the generated CD signal when used as a substrate for detecting chirality of a thin layer of chiral molecules. This eliminates the need to separate the CD signal generated by the array from that of the chiral sample.
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