中文摘要：

用全矢量平面波方法与多极方法联合数值研究六重对称带隙型光子晶体光纤的基模特性.通过全矢量平面波方法可确定组成PBG-PCF的二维光子晶体的带隙,基模（束缚模）存在其频率要落在带隙内且须在k0a=βa的直线附近上部区域,在带隙外形成辐射（泄漏模）.把频率作为输入变量用多极方法计算,数据导出用MATLAB数学软件作出模场分布图,结果发现,不是所有基模可能存在的区域都有基模存在,为带隙型光子晶体光纤的基模寻找提供一种可行的方法.

英文摘要：

Numerical investigation on fundamental mode of PBG-PCF with six-fold rotation symmetry is carried out with full-vector plane wave and multipole method. Band gap of two-photonic crystal, constituting PBG-PCF, is determined by full-vector plane wave method. Frequency of possible existing fundamental modes（bound modes） are not only in band gap but also above line k_0a=βa. Radiation modes exist out of band gap. Multipole method is performed with input frequency as variables. Field distribution of fundamental mode is plotted by MATLAB. It indicates that fundamental modes do not exist in all possible domains. It gives a feasible method to find fundamental modes of PBG-PCF.