厚度递减的光子晶体多通道群延迟的实现

为了改善传统一维光子晶体（PCs）变化单调的群延迟特性，提出一种改进的光子晶体结构.该结构利用了光子晶体反射带在叠加失配时产生的剧烈位相变化性质,以及位相变化和群延迟之间的关联性，在周期结构光子晶体两端添加适当厚度递减周期结构.研究了该光子晶体结构的反射带特性及其对应的群延迟分布，同时比较分析了该结构中高折射率材料与低折射率材料厚度递减时的群延迟特性.结果表明，相对于传统布拉格镜，该结构设计更为自由，而且可以获得多通道的群延迟，从而能够对多波段的光束进行较大且线性的色散分离，实现了更好的滤波效果，在光波分复用领域具备更大的优越性.

Realization of multichannel group delay based on thickness-tapered photonic crystals

In order to improve monotonously variational group delay characteristic in the conventional one-dimensional photonic crystals(PCs),an improved PCs structure was presented.The properties of rapid phase shift for the mismatch induced by the overlaps of different reflective bands inside PCs were utilized in the structure,and the relationship between phase shift and group delay was used,and thickness-tapered period structures were added at the two ends of the periodical PCs.The property of the reflective band was investigated inside the structure,and distribution of corresponding group delay was studied.Group delay properties between two thickness-tapered structures including high refractive index material and low refractive index material were compared and analyzed.The results indicate that compared with traditional Bragg mirrors,the structure design is more free and the structure can achieve multichannel group delay,realize large and linear dispersion at multiwave of light beams,and have better filtering effect and more superiorities in optical demultiplexer system.