含负折射率材料的一维光子晶体中的全向缺陷模

Omnidirectional defect mode of photonic crystals containing negative-index materials

发现由正、负折射率材料交替堆叠构成的一维光子晶体中的零平均折射率(zero-n)带隙中的缺陷模具有3种类型的角度色散,分别为正色散、负色散和近零色散。利用近零色散特性可实现全向缺陷模,此缺陷模的频率在任意角度下均保持不变。研究了具有近零色散的缺陷模与光子晶体的结构参数之间的关系。通过改变光子晶体的结构参数,对缺陷模的近零色散进行优化,实现了分别对应TE波或TM波的单偏振全向缺陷模。此外,发现全向缺陷模的频率不对应光子晶体平均折射率为零的频率,全向缺陷模为光子晶体器件(如全向滤光片)的设计提供了新的思路。

Three kinds of angular dispersion of the defect modes inside the zero-^-n gap in one-dimensional photonic crystal with alternating layers of positive- and dispersive negative-index materials are discovered. These three kinds of angular dispersion are positive-, negative- and near zero-dispersion. Omnidirectional deject modes, which keep the same defect frequent for any incident angle, can be realized by the unique characteristics of the near zero-dispersion. The relations between the near zero--dispersion of the defect mode and the structure of the photonic crystal are also investigated. By the optimization of the structure, it can be obtained that the narrow transmitted frequencies of this kind of defect mode in any one polarization will keep almost unchanging for any incident angle. Moreover, it is found that the frequencies of the omnidirectional defect modes do achieve at the near zero averaged refractive index rather than the condition of exact zero averaged refractive index. The filters based on the principle of these omnidirectional defect modes have many potential applications.