基底对亚波长金属双环结构太赫兹透射性质的影响

太赫兹波通过人工金属亚波长结构开口共振环(SRRs)可以产生共振吸收, 目前普遍采用LC振荡电路和线性振子模型来解释. 利用太赫兹时域光谱系统测得并无开口的亚波长金属双环和反双环结构阵列透射的太赫兹波, 结果仍然观察到在太赫兹透射谱中存在吸收峰. 分析得出此吸收峰的出现可以用线性振子模型解释. 此外, 研究发现若将此结构制作到石英基底上, 当以样品表面法线方向为轴旋转样品时其太赫兹透射时域波形和频谱均会随旋转角度出现明显的周期性变化, 而以硅为基底并不出现此现象. 本文将其原因归结为石英基底的双折射效应对亚波长金属双环结构太赫兹透射性质的影响. 本文主要目的是分析造成这种影响的物理过程.

The effect of substrate on terahertz transmission properties through metal subwavelength dual-ring structure

Terahertz waves through a split-ring resonator (SRR) can induce the resonant absorption, and this can be explained by using the theory of LC resonant circuit and the model of half wave resonance. However, in the dual-ring structure without the split gap, we still observe the resonant absorption in the THz frequency range. By analyzing the phenomenon, we think that it can be explained by using a the model of half wave resonance. Furthermore, it is found that if the structure is fabricated on quartz crystal substrate, we can obtain the angle-dependent terahertz waveforms using terahertz time-domain spectroscopy (TDS) when the sample is rotated in plane, as well as the frequency domain spectra. But this phenomenon does not exist in the silicon-based structure, which may be attributed to the birefringence effect of the quartz crystal substrate on the subwavelength metal dual-ring structure. The main purpose of this article is to explain the physical process of the effect.