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利用传输矩阵方法计算了包含色散媒质缺陷的一维光子晶体的复透射系数 ,其中色散媒质用洛仑兹振子模型描述。计算了由复透射系数定义的等效复折射率并由此研究了频谱位于缺陷模频率附近的光脉冲的群速度。结果发现 ,由于缺陷模附近的透射谱敏感地依赖于缺陷层的光学厚度 ,而缺陷层的色散使缺陷层光学厚度随频率变化而改变 ,从而使包含缺陷的光子晶体的等效色散性质明显地依赖于缺陷的色散行为。由于光脉冲是由多种频率成分的单色场迭加构成的 ,透射脉冲由各单色场透射后重新迭加构成 ,因此波包的传播由介质的等效色散性质决定。与包含无色散缺陷的光子晶体相比 ,缺陷的色散可导致极慢的群速度。通过改变振子强度 ,群速度可从极慢光速转变为超光速 (superluminal)。
The complex transmission coefficient of a one-dimensional photonic crystal containing a dispersion medium defect is calculated using the transfer matrix method, in which the dispersion medium is described by a Lorentz oscillator model. The equivalent birefringence index defined by the complex transmission coefficient is calculated and the group velocity of the optical pulse whose frequency spectrum is near the defect mode frequency is investigated. As a result, it has been found that since the transmission spectrum in the vicinity of the defect mode is sensitively dependent on the optical thickness of the defect layer, the dispersion of the defect layer changes the optical thickness of the defect layer as a function of frequency so that the equivalent dispersion property of the defect- Dependence on defect dispersion behavior. Since the light pulse is composed of monochromatic fields of a plurality of frequency components, the transmission pulse is transmitted by the monochromatic fields and then superimposed on the monochromatic field. Therefore, the propagation of the wave packet is determined by the equivalent dispersion property of the medium. Dispersion of defects can result in extremely slow group velocities compared to photonic crystals that contain achromatic defects. By changing the oscillator strength, the group velocity can change from very slow light speed to superluminal.