金属银膜复合亚波长矩形孔阵列的增强透射

Enhanced optical transmission of composite subwavelength rectangular-hole array based on metal silver thin-film

金属纳米结构由于表面等离激元(Surface Plasmons, SPs)的激发,能够将自由空间的光辐射能量有效耦合到高度受限的表面模式,从而在金属表面纳米尺度范围内形成极大增强的局域场,对宽频带光的收集与激发具有重要意义.为实现金属纳米结构的宽频带高透射率,本文设计了一种复合矩形孔洞式金属微纳结构,并应用时域有限差分法(Finite Difference Time Domain, FDTD)研究了该结构的透射特性.结果表明,与单孔洞阵列相比,该复合孔洞式结构具有光场增强及可调节性等诸多优势,且在透射光谱中可产生多个透射峰.矩形孔洞长度与宽度是影响光透射的主要因素:随着矩形孔洞宽度b的增大,该结构的最大透射率由中心波长526 nm对应的79.7%增大到中心波长为611 nm时对应的88.3%,透射带宽与透射率均有所提高;而矩形孔长度a的变化则会产生奇特的多峰值现象,透射率最高达到93%,透射峰的半高宽最大为354 nm.此外,本文还讨论了中心方孔的边长对该结构阵列透射特性的影响.该研究结果对增强光学透射理论研究的进展以及在新型光学传感器、滤波器、光学透明电极等领域的应用发展有一定的指导意义及应用价值.

Metal nanostructures can effectively couple the optical radiation energy in free space to a highly confined surface mode due to the excitation of surface plasmons(SPs), resulting in a greatly enhanced local field in the nanoscale range of the metal surface, it's great significance for the collection and excitation of broadband light. In order to achieve the broadband and high transmittance of metal nanostructures, a composite rectangular-hole array metal micro/nano structure was designed in this paper, and the transmission characteristics of the structure were studied by using the finite difference time domain(FDTD). The results showed that compared with the single hole array, the compound hole structure has many advantages, such as optical field enhancement, tenability and so on, and there are multiple transmission peaks in the transmission spectrum. In addition, we discussed the effects of the length and width of the rectangular holes on the light transmission characteristics of the structure array. For example, with the increase of the length b of the rectangular hole, the maximum transmittance of the structure increases from 79.7% to 88.3%, and corresponding to the central peak increases from 526 nm to 611 nm. Both the transmission bandwidth and transmittance are improved. While the change of the length a of the rectangular hole produces a peculiar multi-peak phenomenon, the analysis shows that when the length a of the rectangular hole is 250 nm, the maximum transmittance of the full symmetric composite rectangular hole array can reach up to 93% and the FWHM of the transmission peak is 354 nm, much larger than the 80 nm proposed in ref.[27], so the frequency selectivity will be enhanced in the design of the filter. At the same time, the effect of the side length D of the center square hole on the transmission characteristics of the structure array is also discussed. The results of our research have certain guiding significance for the development of enhanced optical transmission theory and application value in the fields of novel optical sensors, t filter and optical transparent electrode.