Cao Hua, Nahata Ajay
Opt Express. 2004 Aug 9;12(16):3664-72. doi: 10.1364/opex.12.003664.
We demonstrate that the resonantly enhanced transmission spectrum associated with a periodic array of subwavelength apertures is dependent upon the shape of the apertures. This is demonstrated using coherent terahertz radiation and aperture arrays fabricated in 75 microm thick stainless steel foils. We examine rectangular apertures with different aspect ratios as well as circular apertures. In the absence of periodicity in the arrays, no resonance features are present. For periodic arrays, we show that the ratio of the transmission coefficients for the two lowest order resonances can be directly related to the ratio of the appropriate aperture dimensions. From the time-domain waveforms, we find two independent, yet phase-coherent, transmission processes: non-resonant transmission related to the simple transmission through subwavelength apertures and a time-delayed resonant transmission related to the interaction of the THz pulse with the periodic aperture array. In these waveforms, we also observe a sign inversion for the primary bipolar pulse relative to the reference. This is shown to be a simple consequence of diffraction.
我们证明，与亚波长孔径的周期性阵列相关的共振增强透射光谱取决于孔径的形状。这是通过使用相干太赫兹辐射和在75微米厚的不锈钢箔中制造的孔径阵列来证明的。我们研究了具有不同纵横比的矩形孔径以及圆形孔径。在阵列中不存在周期性的情况下，不存在共振特征。对于周期性阵列，我们表明两个最低阶共振的透射系数之比可以直接与适当的孔径尺寸之比相关。从时域波形中，我们发现了两个独立但相位相干的透射过程：与通过亚波长孔径的简单透射相关的非共振透射，以及与太赫兹脉冲与周期性孔径阵列的相互作用相关的时延共振透射。在这些波形中，我们还观察到相对于参考的初级双极脉冲的符号反转。这被证明是衍射的一个简单结果。
