We present a new structure of nearly-zero flattened dispersion and highly nonlinear photonic crystal fiber (PCF) in the telecommunication window. This fiber design is comprised of a hybrid-core region with -bismuth-doped region in the center and three lower bismuth-doped regions in the first ring that enables dispersion control while maintaining a high nonlinear coefficient. Numerical analysis results show that the proposed PCF is achieved with a nonlinear coefficient of about 3301 W-1 km-1, a dispersion value of about 0.5537 ps/(nm·km) at 1550 nm, and nearly-zero flattened dispersion fluctuating within 2.5 ps/(nm·km) ranging from 1.496 to 1.596 μm.

The dispersion compensation properties of dual-concentric core photonic crystal fibers are theoretically investigated in this letter. The effects of geometric structure on the dispersion properties of dual-concentric core photonic crystal fibers are carefully studied by finite element method. The first layer of holes around the core area is enlarged in a new manner with the near-core point fixed. Considering the tradeoff among several parameters, results show that the dispersion compensation wavelength and strength can be tuned to desired values by constructing an appropriate design of the geometric structure of photonic crystal fibers.

从矩形空气孔光子晶体平板的研究入手，设计了一种新型的正方形空气孔L3型光子晶体平板微腔。采用有限时域差分法，计算了正方形空气孔L3型光子晶体微腔的Q值、模体积及谐振频率；讨论了正方形空气孔边长对微腔Q值、模体积及谐振频率的影响。对L3型光子晶体平板微腔进行了优化，设计出了Q值为27719、模体积为0.4361(λ/n)3、谐振波长为1543 nm的正方形空气孔的L3型光子晶体平板微腔。该L3型光子晶体平板微腔的Purcell因子高达4767。

采用有限元法，计算了二维三角晶格椭圆形格点空气孔型光子晶体的TE、TM模式的带隙结构。通过对椭圆形空气孔格点的大小、方向进行改变，研究了填充比、格点方向对带隙的影响。计算结果表明，在空气孔型光子晶体中TE模式更容易形成带隙；不同填充比情况下，格点方向对TE模式和TM模的带隙变化都具有不同影响；不论格点方向如何变化，均未出现完全带隙。

采用全矢量有限元法, 研究了圆柱形介质柱、正方形格子的光子晶体波导耦合器的传输特性, 计算了不同耦合长度波导耦合器的分光比, 以及同一耦合长度下不同波长时的分光比, 并分析了改变介质柱折射率后的分光比。计算分析结果表明, 可以通过改变光子晶体波导耦合器的某些结构参数来控制各出口处的分光比, 实现光在传播过程中的平移、反向和分岔, 以满足光信息传输和处理的要求。