用多极方法数值研究了六重对称全内反射型光子晶体光纤(C6v TIR-PCF)在1.55 μm波长处基模有效面积与包层空气孔层数、直径、间距和相对孔径的关系。结果表明层数的影响较小，在单一参数变化时有效面积随空气孔直径的变大而减小，随间距的增大而变大，在层数与相对孔径一定时有效面积随空气孔半径与间距的同比增大而增大。

Localized fields in the defect mode of one-dimensional photonic crystals with active impurity are studied with the help of the theory of spontaneous emission from two-level atoms embedded in photonic crystals. Numerical simulations demonstrate that the enhancement of stimulated radiation, as well as the phenomena of transmissivity larger than unity and the abnormality of group velocity close to the edges of photonic band gap, are related to the negative imaginary part of the complex effective refractive index of doped layers. This means that the complex effective refractive index has a negative imaginary part, and that the impurity state with very high quality factor and great state density will occur in the photonic forbidden band if active impurity is introduced into the defect layer properly. Therefore, the spontaneous emission can be enhanced, the amplitude of stimulated emission will be very large and it occurs most probably close to the edges of photonic band gap with the fundamental reason, the group velocity close to the edges of band gap is very small or abnormal.

The refraction and reflection of Gaussian beam on two-dimensional photonic crystal (2DPC) slab are studied by the finite-difference time-domain (FDTD) method. It is shown that 2DPC slab enables negative refraction, which is demystified by the distribution of Poynting vector directions and values inside the 2DPC. A negative Goos-Hanchen shift is also found in the simulation.

Using numerical simulation method based on finite-difference time-domain (FDTD), we study the characteristics of the multiple-core photonic crystal fibers (PCFs) in which square-nested compound lattices (SNCLs) with several defect regions are introduced. We find that each line defect in the PCFs can serve as a channel in wavelength division multiplexing (WDM) communication systems. The crosstalk can be suppressed because there is a band gap among each channel in the PCFs. And PCF amplifiers are expected to be used in the super-dense WDM systems.

The coupling characteristics of two defect modes in photonic crystal fibers are investigated theoretically by the finite-difference time-domain (FDTD) method. The transmission spectrum and eigenmodes of optical wave are found to be very sensitive to the geometrical and physical parameters of the structure, as well as to the relative position of the two defects.