Opt Lett. 2013 Dec 15;38(24):5216-9. doi: 10.1364/OL.38.005216.
We investigate Fano resonances in planar two-dimensional periodic arrays of linear trimers of plasmonic nanoparticles that appear under plane wave incidence. The observed Fano resonances are associated to resonances belonging to the trimer (metamolecule) itself, where some are found to be strongly affected by the array periodicity. We observe that array-dependent resonances appearing for oblique incidence are resistant to losses, whereas narrow dipolar-like Fano resonances associated mainly to the metamolecule, which appear also under normal incidence, disappear when losses are too high. In particular, we prove the latter by theoretical (dipolar approximation) and full-wave simulations, in good agreement. We propose that the use of very low-loss plasmonic materials or the use of gain materials to mitigate plasmonic losses may lead to (high-quality factor) dipolar-like Fano resonances under normal incidence, exhibiting a certain degree of fabrication defect tolerance, which might be employed to improve sensors, lasing, switching, and nonlinear devices, for example.
我们研究了在平面波入射下出现的等离子体纳米粒子线性三聚体的二维周期性阵列中的 Fano 共振。观察到的 Fano 共振与三聚体（超分子）本身的共振有关，其中一些共振强烈受到阵列周期性的影响。我们观察到，对于斜入射出现的与阵列相关的共振对损耗具有抵抗力，而与超分子主要相关的窄偶极子型 Fano 共振，也在正常入射下出现，当损耗过高时会消失。特别是，我们通过理论（偶极子近似）和全波模拟证明了后者，结果非常吻合。我们提出，使用非常低损耗的等离子体材料或使用增益材料来减轻等离子体损耗，可能会导致在正常入射下出现（高品质因数）偶极子型 Fano 共振，并表现出一定程度的制造缺陷容忍度，这可能用于改善传感器、激光、开关和非线性器件等。
