Department of Physics, Department of Chemistry, and JILA, University of Colorado, Boulder, Colorado 80309, USA.
Opt Lett. 2013 Apr 15;38(8):1322-4. doi: 10.1364/OL.38.001322.
We study the decrease in group velocity of broadband surface plasmon polariton propagation on a conical tip, using femtosecond time-domain interferometry. The group delay of (9±3) fs measured corresponds to a group velocity at the apex of less than 0.2c. The result agrees in general with the prediction from adiabatic plasmonic nanofocusing theory, yet is sensitive with respect to the exact taper geometry near the apex. This, together with the sub 25 fs(2) second-order dispersion observed, provides the fundamental basis for the use of plasmons for broadband slow-light applications.
我们使用飞秒时域干涉法研究了锥形尖端上宽带表面等离激元传播的群速度下降。测量得到的群延迟（9±3）fs 对应于尖端处小于 0.2c 的群速度。该结果与绝热等离激元纳米聚焦理论的预测大致相符，但对尖端附近的精确锥形几何形状较为敏感。这一点，再加上观察到的 25fs(2)以下的二阶色散，为等离激元在宽带慢光应用中的使用提供了基本依据。
