The unit cell of a frequency selective surface (FSS) consisting of asymmetric split-ring resonators (SRR) is investigated using an apertureless (scattering) near-field terahertz time domain microscope based on a scanning tunnelling microscope. Images displaying a high frequency-independent resolution of 1/60 - 1/200 is obtained over a broad spectral range (0.3…1 THz) using high-speed asynchronous optical sampling. The images reveal the structure of the resonator arcs, additionally they show an increase of the signal around the end of the resonators. The behaviour of the relative near-field signal intensities from the two different arcs with frequency can be related to the fundamental resonances of the SRRs.%利用基于扫描遂道显微成像技术的无孔(散射)近场太赫兹时域显微镜,对由非对称开口谐振环(SRR)构成的频率选择表面(FSS)的单元进行了研究.利用高速非同步光学采样法,在宽频率范围(O.3… 1THz)内获得了1/60-1/200的高频独立分辨率的图像显示.该图像给出了谐振环的弧状结构,另外,还显示了谐振环的弧末端周围的信号增强.结果显示,从两个不同弧发出的相对近场信号强度的特性与SRRs本征共振频率是相关联的.
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