Abstract: The finite-difference time-domain method is used to calculate the electronic field distribution and enhancement factor of nano-scale optical antennas for different shape, length and substrates. When the resonant wavelength is 915 nm, the antenna with symmetry echelon dipoles has an enhancement factor of 1 739, which is greater than the enhancement factor of 1 076 of the antenna with symmetry rectangle dipoles. The resonant wavelength has a blue-shift when the length of the antenna is decreased. With a glass substrate, the resonant peak of the antenna with a length of the dipole of 80 nm red-shifts from 587?nm to 715 nm and the electric field distribution inclines to the substrate.

Key words: resonant optical antennas, surface plasmons, finite-difference time-domain

摘要： 利用有限时域差分方法计算和分析了天线形状、臂长、衬底等对纳米尺度下的光学天线场分布和场增强的影响。在915 nm处共振时，梯形对称振子天线的场增强因子为1 739，比长方形对称振子天线的增强因子1 076要大；天线臂长的减小，使得共振波长蓝移。当单个振子长度为80 nm时，玻璃衬底的引入使天线共振峰从587 nm红移至715 nm，并使场分布偏向衬底。

关键词: 光学共振天线, 表面等离激元, 时域有限差分方法