【作者】 刘念华； 朱诗尧；

【Author】 LIU Nian-Hua1 and ZHU Shi-Yao2 1Department of Physics, Nanchang University, Nanchang, 330047 2Department of Physics, Hong Kong Baptist University

【机构】 南昌大学物理系； 香港浸会大学物理系；

【摘要】 利用通过一维光子晶体复透射系数可定义光子晶体的等效折射率。在光子晶体的带隙中,等效折射率具有反常色散的行为。这种反常色散可导致光脉冲的超快光(superluminal)传播。若在光子晶体中引入缺陷,则在带隙中的缺陷模附近等效折射率是正常色散的,且有陡峭的变化,使光脉冲出现极慢光传播。本文研究光脉冲通过光子晶体的超快光速与极慢速光现象,通过研究各Fourier分量在复平面上的演化表明,在反常色散区,这些Fourier分量迭加后将使脉冲的峰前移,在正常色散区,这些Fourier分量迭加后将使脉冲的峰滞后。色散介质中超快光与极慢光现象是组成光脉冲的各Fourier分量通过介质时获得不同相移后重新相干迭加干涉的结果。更多还原

【Abstract】 The effective refractive index can be defined by using the complex transmission coefficient. The effective refractive index is anomalously dispersive within the photonic gap of the photonic crystals. The anomalous dispersion causes to the superluminal propagation of light pulses. If a defect is put in the photonic crystals, the behavior of the dispersion around the defect mode becomes normal with positive steep slope, which leads to ultraslow propagation. In this paper we investigate the superluminal propagation and ultraslow propagation of the pulses. From the evolution behavior of each Fourier component we find that in the anomalously dispersive region, the peak at the exit end appears in advance, while in the normally dispersive region, the peak is lagged. Since the pulse is formed by the superposition of the Fourier components, we conclude that the superluminal propagation or ultraslow propagation of the pulses is a result of the interference of the Fourier components with different phase shifts.更多还原