用时域有限差分方法模拟了两种光偶极天线模型的场分布,研究了光偶极天线的远场辐射特性随其长度增加而变化的规律以及影响其远场方向性的因素,发现光偶极天线的远场方向性随其长度增加而变化的规律类似于经典对称振子天线的相应规律.但高阶局域表面等离激元模式的存在使得光偶极天线的远场辐射图更快地出现了旁瓣.这些发现对于提高光天线的性能具有重要意义. The field distribution of the two dipole antenna models was simulated by the finite difference time domain method. The law of the far-field radiation characteristics of the dipole antenna changing with its length and the factors affecting its far-field directivity were studied. The regularity that the far-field directivity of the polar antenna changes with its length is similar to that of the classical symmetric dipole antenna, but the existence of the high-order local surface plasmon polarizer makes the far-field radiation pattern of the optical dipole antenna faster Appear side lobe These findings are of great significance to improve the performance of the optical antenna.