Nguyen Tho Duc, Nahata Ajay, Vardeny Z Valy
Department of Physics, University of Utah, Salt Lake City, Utah 84112, USA.
Opt Express. 2012 Jul 2;20(14):15222-31. doi: 10.1364/OE.20.015222.
Using terahertz (THz) transmission measurements through two-dimensional Fibonacci deterministic subwavelength hole arrays fabricated in metal foils, we find that the surface plasmon-polariton (SPP) correlation lengths for aperiodic resonances are smaller than those associated with the underlying grid. The enhanced transmission spectra associated with these arrays contain two groups of Fano-type resonances: those related to the two-dimensional Fibonacci structure and those related to the underlying hole grid array upon which the aperiodic Fibonacci array is built. For both groups the destructive interference frequencies at which transmission minima occur closely match prominent reciprocal vectors in the hole array (HA) structure-factor in reciprocal space. However the Fibonacci-related transmission resonances are much weaker than both their calculated Fourier intensity in k space and the grid-related resonances. These differences may arise from the complex, multi-fractal dispersion relations and scattering from the underlying grid arrays. We also systematically studied and compared the transmission resonance strength of Fibonacci HA and periodic HA lattices as a function of the number of holes in the array structure. We found that the Fibonacci-related resonance strengths are an order of magnitude weaker than that of the periodic HA, consistent with the smaller SPP correlation length for the aperiodic structure.
通过对金属箔中二维斐波那契确定性亚波长孔阵列进行太赫兹（THz）传输测量，我们发现非周期共振的表面等离激元极化激元（SPP）相关长度小于与底层网格相关的长度。与这些阵列相关的增强传输光谱包含两组法诺型共振：一组与二维斐波那契结构相关，另一组与构建非周期斐波那契阵列的底层孔网格阵列相关。对于这两组共振，传输最小值出现时的相消干涉频率与倒易空间中孔阵列（HA）结构因子中的显著倒易矢量紧密匹配。然而，与斐波那契相关的传输共振比其在k空间中的计算傅里叶强度以及与网格相关的共振都要弱得多。这些差异可能源于复杂的多重分形色散关系以及来自底层网格阵列的散射。我们还系统地研究并比较了斐波那契HA和周期性HA晶格的传输共振强度随阵列结构中孔数量的变化。我们发现，与斐波那契相关的共振强度比周期性HA的共振强度弱一个数量级，这与非周期结构较小的SPP相关长度一致。
