The mode field distributions at different wavelengths in the first bandgap of all-solid photonic bandgap fibers were numerically studied by multipole method.The corresponding 2D distributions of the normalized intensity were obtained by the same method.The mode field distributions in x and y directions were shown as the two directions were representative in the fiber with six-fold rotational symmetry.In the long-wavelength regime the mode field radii in the two directions are not equal and both decrease as the wavelength increases, which is different from the change in total internal reflection fibers.%利用多极法计算了全固态光子带隙光纤第1带隙内不同波长处的基模模场分布,得到2维归一化光强分布特性.由于该光纤具有三角形(C<,6v>)的对称结构,影响了光纤内的模场分布,为此计算了该结构两个具有代表性的方向上的模场分布,分析了带隙内两个不同的结构方向上的模场分布特性.结果表明.在长波长区域,两个方向上的模场半径并不相等,但都随波长的增加而减小,其变化规律与全内反射导光的光纤不同.
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