中文摘要：

提出了一种低对称性椭圆介质柱二维光子晶体结构，利用平面波展开法研究了该结构在第一布里渊区的能带特性．讨论了全角自准直效应的物理机制及椭圆柱结构参数对其带宽的影响，明确给出了自准直传播模式的存在判据．研究发现，自准直模式几乎覆盖了TE偏振的整个第四能带，而且该能带面上存在两个横跨第一布里渊区的超宽平坦区域．时域有限差分法模拟结果表明，利用超宽平坦区域的特性，可同时实现带宽达187nm（以1550nm为中心波长）、准直入射角度几乎覆盖0°-90°的宽带全角自准直光传输．

英文摘要：

We propose a two-dimensional photonic crystal structure with low rotational symmetry and investigate its band structure characteristics over the whole first Brillouin zone by the plane wave expand method. The physical mechanism of broadband all-angle self-collimation effect and the influence of aspect ratio on the bandwidth are clarified. Furthermore, we obtain the existence criterion for self-collimation modes covering almost the whole fourth band for TE polarization. Especially, there exist two wide fiat regions spanning over the first Brillouin zone which exhibit unique properties： one dimension corresponds to broad band from 0.47 to 0.53 （2πc/a）, while the other corresponds to all incident angles of 0°-90°. Based on the above unique properties, the broadband all-angle self-collimation propagation with a bandwidth of 187 nm around 1550 nm is demonstrated by the finite-difference time-domain method.