光子晶体光纤色散极值特性的研究

采用全矢量有效折射率法计算光子晶体光纤的色散系数,深入分析了光子晶体光纤色散系数与结构参数之间的关系,发现色散系数随着结构参数的变化具有双极值特性:1)当Λ值保持不变时,随着d/Λ值的减小,零色散波长向长波方向移动,在达到极大值后,则转向短波方向移动,例如当Λ=2.3μm时,极大零色散波长出现在约d/Λ=0.24处,约为1728.9nm,当Λ取不同值时,较小的Λ值,会对应有较大的极大零色散波长;2)当d/Λ值保持不变时,随着Λ值的减小,零色散波长向短波方向移动,在达到极小值后,则转向长波方向移动,例如当d/Λ=0.9时,极小零色散波长出现在约Λ=0.6μm处,约为564.29nm,当d/Λ取不同值时,该比值越大,则会对应着越小的极小零色散波长。这一发现对于优化设计特种光子晶体光纤具有一定的价值。

Study on the Extreme Characteristics of Dispersion of Photonic Crystal Fiber

With a fully vectorial effective index method, the total dispersion coefficient of photonic crystal fiber is calculated, and it is deeply analyzed that how the total dispersion coefficient is affected by the structural parameters. It is found that the dispersion coefficient has two-extreme characteristics with the changes of structural parameters. 1) When Λ is unchanged, with the reduction of d/Λ, the zero-dispersion wavelength (ZDW) moves to the long wavelength. After reaching the maximum ZDW (MZDW), instead, the ZDW moves to the short wavelength. For example, when Λ=2.3 μm, the MZDW is about 1728.9 nm, as d/Λ=0.24, and the smaller Λ has the longer MZDW than the larger. 2) When d/Λ is unchanged, with the reduction of Λ, the ZDW moves to the short wavelength. After reaching the minimum ZDW (M-ZDW), the ZDW moves to the long wavelength. For example, when d/Λ=0.9, the M-ZDW is about 564.29 nm, as Λ=0.6 μm, and the larger d/Λ has the shorter M-ZDW than the smaller. These discoveries could be used to optimize design of the special photonic crystal fiber.