提出一种金属-介质-金属非对称圆形结构,该结构由两个圆形谐振腔、一个传输波导和两个耦合波导组成。利用谐振腔的局域作用加强表面等离激元的耦合作用,获得较大的透射率。采用有限时域差分方法研究了圆形谐振腔半径、个数和两圆腔中心距离对强透射特性的影响。结果表明,当非对称圆形谐振腔的半径为100 nm、两圆间距为200 nm时,该结构具有较高的透射率。通过优化主要参数,所设计结构的平均阻带宽度为1000 nm,工作范围可增大到2500 nm。

Herein, a metal-insulator-metal asymmetric circular structure comprising two circular cavities, a transmission waveguide, and two coupled waveguides is proposed. The coupling effect of surface plasmon polaritons is strengthened through the local effect of resonant cavities, and a good extraordinary transmission is obtained. The effects of the radii and number of circular resonant cavities and that of the inter-circle distance on such an extraordinary transmission are investigated via the finite difference time domain method. The results show that in the case that the radius of the circular resonant cavity resonator and the inter-circle distance are 100 nm and 200 nm, respectively, the structure exhibits a very good extraordinary transmission. The optimization of these main parameters could allow an average stopband width of 1000 nm and increase the working range up to 2500 nm.