Optimal plasmonic focusing on a metal disc under radially polarized terahertz illumination
Optimal plasmonic focusing on a metal disc under radially polarized terahertz illumination
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DOI：
10.1088/1367-2630/15/7/075005
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发表时间：
2013-07
影响因子：
3.3
通讯作者：
S. Waselikowski;C. Fischer;J. Wallauer;M. Walther
中科院分区：
文献类型：
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作者：
S. Waselikowski;C. Fischer;J. Wallauer;M. Walther
研究了在径向极化太赫兹脉冲照射下，金属圆盘中心表面等离子体激元的最佳聚焦。通过将金属结构的圆柱对称与径向极化太赫兹场相匹配，表面等离子体激元沿其整个圆周被激发。在光盘中心的建设性干涉产生一个尖锐的频率依赖的焦点点很好地描述了零阶贝塞尔函数。我们用太赫兹（THz）近场显微镜绘制了圆盘上的场分布，并将我们的结果与数值模拟进行了比较。为了比较，我们还描述了等离子体透镜在线偏振太赫兹照射下的行为。这种等离子体透镜的聚焦能力及其简单的结构为太赫兹传感和成像应用提供了巨大的潜力。
Optimal focusing of surface plasmon polaritons in the center of a metal disc illuminated by radially polarized terahertz pulses is demonstrated. By matching the cylindrical symmetry of the metal structure with the radially polarized terahertz field, surface plasmons are excited along its entire circumference. Constructive interference in the disc center produces a sharp frequency-dependent focal spot well described by a zero-order Bessel function. We map the field distributions on the disc by terahertz (THz) near-field microscopy and compare our results with numerical simulations. For comparison, the behavior of the plasmonic lens under linearly polarized THz illumination is also characterized. The remarkable focusing capabilities of such a plasmonic lens together with its simple structure offer considerable potential for THz sensing and imaging applications.