运用有限差分法模拟二维无界区域maxwell方程的电磁波传播，电磁场为横向电场传播，为了将无界问题等价地转化为可数值模拟的有界问题，我们采用了PML技术，将向外传播的电磁波吸收- Electromagnetic wave propagation using a two-dimensional finite difference method unbounded domains maxwell equation for the transverse electromagnetic field