Shou Xiang, Agrawal Amit, Nahata Ajay
Opt Express. 2005 Nov 28;13(24):9834-40. doi: 10.1364/opex.13.009834.
We have measured the enhanced transmission properties of periodic arrays of subwavelength apertures fabricated in thin metal films as a function of the metal film thickness. In doing so, we determine the minimum metal film thickness for an array that exhibits resonantly enhanced transmission and observe the transmission properties as the metal film thickness is increased. The thickness range explored extends from delta/15, where delta is the skin depth, to approximately 2delta. Using terahertz time-domain spectroscopy, we measure both the amplitude and phase of the transmitted broadband THz pulses. Experimentally, we find that there is negligible transmission enhancement for metal films as thin as delta/15. As the film thickness increases, there is a sublinear increase in the enhancement until the film thickness is equal to the skin depth. For metal films thicker than one skin depth, there appears to be little additional enhancement at the resonant frequencies. We also observe that as the thickness of metal films increases, there is a corresponding increase in the resonance frequencies.
我们已测量了在薄金属膜中制备的亚波长孔径周期阵列的增强传输特性，并将其作为金属膜厚度的函数进行研究。在此过程中，我们确定了表现出共振增强传输的阵列的最小金属膜厚度，并观察了随着金属膜厚度增加时的传输特性。所探索的厚度范围从δ/15（其中δ为趋肤深度）延伸至约2δ。使用太赫兹时域光谱技术，我们测量了透射宽带太赫兹脉冲的幅度和相位。实验中，我们发现对于厚度仅为δ/15的金属膜，传输增强可忽略不计。随着膜厚度增加，增强呈现亚线性增加，直至膜厚度等于趋肤深度。对于厚度大于一个趋肤深度的金属膜，在共振频率处似乎几乎没有额外的增强。我们还观察到，随着金属膜厚度增加，共振频率相应增加。
