利用最小二乘拟合法分析了光子晶体的能带结构，定量分析了二维光子晶体的色散参量.为了考虑脉冲各频率的作用，通过引入与频率分量相关的权重因子，从而解析了群速度和平均群速度色散，进而解析出脉冲波络渐变的理论结果.通过FDTD数值模拟后，发现数值模拟结果与理论解析结果完全相吻合.本文处理光子晶体的色散参量的方法，为制作光子晶体色散器件如光子晶体色散补偿器、脉冲展宽和压缩器有一定的借鉴作用.

Using the least-squares spline approximation to analyze the photonic band structure, the dispersion parameters of a two-dimensional photonic crystal are quantitatively calculated. Considering the large bandwidth of an ultrashort pulse, average group velocity and average group velocity dispersion are achieved by introducing a weighting factor, which reveals the share of different frequency components. So the pulse evolution can be predicted theoretically. Propagation of ultrashort pulses through the photonic crystals is simulated by using the finite-difference time-domain method. The results of numerical simulations are well consistent with the theoretical predictions. This process for achieving dispersion parameters is valuable for designing photonic-crystal dispersion devices such as dispersion compensator, pulse compressor and pulse stretcher.