截面形状对快电子激发纳米双线表面等离激元的影响

摘要

采用边界元方法研究了快电子在金属纳米双线中激发间隙表面等离激元(SPP)的性质,比较了在不同横截面形状(包括圆形、尖劈形和不规则形状)下电子所激发SPP的不同.研究表明:在以上波导结构中,快电子都能激发具有较长传播距离和较好局域性的低阶单级-单级耦合的间隙等离激元模式;同时通过对波导无量纲价值参数的比较,发现快电子在纳米双线中激发间隙等离激元对双线波导的横截面形状要求不高,横截面形状真正影响的是高阶等离激元模式的激发,而且快电子在截面形状为尖劈的双线波导中能激发局域性更强的间隙SPP.该研究将对实验中利用电子显微镜手段实现SPP间隙模式的激发具有指导意义.%In this paper,we investigate the gap plasmon excitation by swift electron beams in nanowire pairs, in particular, with different cross-section shapes (including circular, wedge and irregular shape). For all these nanowire pairs, our results show that fast electron beams can efficiently excite low-order monopole-monopole gap plasmons, which possess long propagation distance and well spatial localization. Furthermore, in contrast to high-order plasmons, the excited gap plasmons do not depend highly on cross-section shape of nanowire pairs through comparing the merit parameters in these three kinds of waveguides. Besides, the excited gap mode will be more confined in nanowire pairs with wedge cross-section. Our study will be helpful for the experiments of gap plasmon generation using electron microscope.