说明： 有限差分法求解波导等效折射率，以及横模场分布，适合 矩形波导，脊波导等 微纳米级别的有源或无源光器件的数值仿真。 (The finite difference method (FDM) is suitable for the numerical simulation of active and passive optical devices at micro and nano levels, such as rectangular waveguides and ridge waveguides.)
