Jen Yi-Jun, Lin Po-Chun, Lo Xing-Hao
Department of Electro-Optical Engineering, National Taipei University of Technology, Taipei, 106, Taiwan.
Sci Rep. 2022 Aug 10;12(1):13611. doi: 10.1038/s41598-022-17703-0.
In this work, an ultra-thin silver film-coated grating as a split silver nanotube array exhibits not only high TE polarized reflectance as a conventional subwavelength grating but also high TM polarized reflectance that is close to or higher than TE reflectance at certain wavelength range. The TM reflectance peak shifts with the morphology of the silver covering. The near-field analysis reveals that the silver nanotube array is an ultra-thin optical double negative metamaterial. The negative permeability associated magnetic field reversal is induced within the grating that is surrounded by a split current loop at the TM reflectance peak wavelength. The near field simulation is used to retrieve the equivalent electromagnetic parameters and optical constants that cause the anomalous TM high reflection. It is demonstrated that the TM impedances have a low magnitude and high magnitude with respect to unity for light incident onto the top and bottom of the grating at the peak wavelength, respectively.
在这项工作中，一种作为分裂银纳米管阵列的超薄银膜涂层光栅，不仅像传统亚波长光栅一样具有高TE偏振反射率，而且在特定波长范围内还具有接近或高于TE反射率的高TM偏振反射率。TM反射峰随银覆盖层的形态而移动。近场分析表明，银纳米管阵列是一种超薄光学双负超材料。在TM反射峰波长处，由分裂电流环包围的光栅内会感应出与负磁导率相关的磁场反转。利用近场模拟来获取导致异常TM高反射的等效电磁参数和光学常数。结果表明，在峰值波长下，对于入射到光栅顶部和底部的光，TM阻抗相对于单位值分别具有低幅值和高幅值。
