内嵌凹槽的金属亚波长狭缝共振透射特性分析

Analysis of the resonance transmittance properties of metallic subwavelength slit with an embedded groove

在亚波长金属狭缝内嵌入凹槽后,狭缝的透射峰发生红移、蓝移,也可能不变。本文利用有限时域差分法,详细讨论了内嵌凹槽深度对狭缝透射光谱的影响。通过与腔共振模式理论对比,我们发现内嵌凹槽的亚波长金属狭缝透射峰变化一方面来自于共振腔长度的增长,另一方面来自于透射峰所对应的共振模式数的增加。透射峰蓝移等变化均为共振模式数改变和共振腔长度增长共同作用的结果。

The subwavelength metal slit changes in its transmittance properties if embedded with a groove inside.Red-shift,blue-shift or no shift may happen.In this work,we study the dependence of the transmission spectrum of slit on the depth of the embedded groove by using the finite difference time domain method.Compared with the results from cavity resonance mode theory,we find that the shift situation of the subwavelength metal slit comes from two reasons,the increase in the cavity length and the increase in the resonance mode number.The spectrum changes,such as blue-shift,are the hybrid results of the increase in both of the mode number and the cavity length.