以電磁理論模擬探討與尋找新奇負折射超穎材料

Abstract

我們提出一種新的負折射超穎材料(Negative index metamaterial)，其單元是由一對站立 U 形環所組成的人工原子(meta-atom)，並用有限元素法(Finite element method)對此系統進行數值模擬與分析。此種超穎材料的等效介電常數(effective permittivity)與導磁係數(effective permeability)在近紅外波長區間內[1080nm~1260nm]同時為負值，因此在相當寬的頻寬內(180nm)具有等效的負折射率(n~-2)。此外，我們還優化系統的幾何參數，使得系統的等效阻抗與外界空氣匹配(impedance matching , z~1)，並且系統的品質因子(figure of merit)在1200nm左右達到最高值(FOM=20.6)。最後，我們用這個超穎材料做了一個單層平板和一個楔形稜鏡，並對這兩個系統 做了數值模擬(numerical simulations)，証明這種超穎材料的確具有負折射現象。

Negative index metamaterial composed of the upright split-ring pair as one meta-atom has been investigated numerically by finite element method. This new metamaterial possesses both negative effective permittivity and negative effective permeability overlapping in the near-infrared region [1080nm~1260nm], hence exhibiting a negative index of refraction (n~-2) with a broad double negative bandwidth (180nm). We also tune the geometric structure parameters to optimize the metamaterial, thus achieving a good impedance matching (z~1) and a rather high figure of merit (FOM=20.6) at the wavelength around 1200nm. Finally, numerical simulations demonstrate that both single-layer system and wedge-shape lens made of the split-ring pairs show the negative refraction phenomenon.