通过引入磁光材料的非互易回转因子，形成新型光束传播方法（BPM），从而计算磁光波导的非互易效应。磁光波导参数可调，非互易回转因子可调。-calculate the nonreciprocal effect of magneto-optical waveguide using the beam-propagation method based on nonreciprocal element.