We investigate four types of gold nanoantennae (the monopole, the dipole, the cone-shaped, and the cone-bowtie antenna), under a fixed working wavelength. The finite-difference time-domain (FDTD) simulations show that the near-field enhancement values do not increase monotonously when the antennae sizes decrease, and optimization conditions vary with the antenna shapes. We also propose a distributed dipole ring model to analytically calculate the near field. The size condition for the strongest enhancement is the compromising result of the total radiated energy and the near-field distribution factor. Assuming the cone-bowtie antenna is the best for high enhancement, the maximum potential in near-field enhancement is 2 x 10(5) for a linear signal or 4 x 10(10) for typical nonlinear signals. (C) 2015 Optical Society of America
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机译：在固定的工作波长下，我们研究了四种类型的金纳米天线（单极天线，偶极天线，圆锥形天线和锥领天线）。有限差分时域（FDTD）仿真表明，当天线尺寸减小时，近场增强值不会单调增加，并且优化条件会随天线形状的变化而变化。我们还提出了一个分布式偶极环模型来分析计算近场。最强增强的大小条件是总辐射能量和近场分布因子的折衷结果。假定锥形领结天线是最佳的高增强天线，则对于线性信号，近场增强的最大电势为2 x 10（5），对于典型的非线性信号，为4 x 10（10）。 （C）2015年美国眼镜学会
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