Gutha Rithvik R, Sadeghi Seyed M, Sharp Christina, Hatef Ali
Department of Physics and Astronomy, University of Alabama in Huntsville, Huntsville, Al, 35899, United States of America. Nano and Micro Device Center, University of Alabama in Huntsville, Huntsville, AL, 35899, United States of America.
Nanotechnology. 2019 Sep 27;30(39):395203. doi: 10.1088/1361-6528/ab2ce8. Epub 2019 Jun 26.
We study the anomalous optical properties of lattices formed via periodic arrangement of a plasmonic unit structure consisting of a metallic nanorod and U-shape split-ring resonator. When the units are closely packed, i.e., small lattice constants, and the incident light is polarized along the transverse axis of the nanorods, our results show that the near-field plasmonic coupling of these units leads to a lattice-induced meta-mode. Such a meta-mode is not an intrinsic mode of these units or their constituents (nanorods and split-ring resonator), rather it is formed via capacitive coupling of the split-ring resonator of one unit with the nanorod of another unit. This leads to a unique charge distribution, generating a strong field accumulation at the center of the nanorod. We show that this assimilates a plasmon field profile similar to that of the intrinsic quadrupole mode of the nanorods, although it occurs at wavelengths longer than their dipole modes. Our results show that such a meta-mode generates a narrow dominant optical feature in the infrared range (∼1.5 μm) with significant immunity against the rotation of the lattices.
我们研究了通过由金属纳米棒和U形开口环谐振器组成的等离激元单元结构的周期性排列形成的晶格的异常光学特性。当这些单元紧密堆积时，即晶格常数较小时，并且入射光沿纳米棒的横向轴偏振，我们的结果表明，这些单元的近场等离激元耦合会导致晶格诱导的元模式。这种元模式不是这些单元或其组成部分（纳米棒和开口环谐振器）的本征模式，而是通过一个单元的开口环谐振器与另一个单元的纳米棒之间的电容耦合形成的。这导致了独特的电荷分布，在纳米棒的中心产生了强烈的场积累。我们表明，这类似于纳米棒的本征四极子模式的等离激元场分布，尽管它发生在比其偶极模式更长的波长处。我们的结果表明，这种元模式在红外范围（~1.5μm）产生一个窄的主导光学特征，并且对晶格的旋转具有显著的抗性。
