模拟了带有模式扩展层的半导体激光器，研究了中心波导层、扩展波导层和内限制层对激光器性能的影响。经过优化获得了一个条宽为50 μm，远场发散角为23°，阈值电流为117.8 mA，限制因子为2.37%的激光器。远场发散角最小可达到18°，此时阈值电流为200.9 mA。与普通结构比较，优化后的结构远场垂直发散角减小了20°左右，阈值电流并没有明显增加，模拟计算表明模式扩展层没有降低激光器的电学和温度稳定特性。

The impact of center waveguide layers, mode expansion layers and confinement layers on semiconductor laser performance with mode expansion layers has been investigated using the crosslight software. A structure with stripe width of 50 μm and far field divergence angle of 23° is obtained, whose threshold current is 117.8 mA and confinement factor is 2.37%. The far field divergence angle can be as low as 18° when the threshold current is 200.9 mA. After optimization the far field vertical divergence angle is reduced by about 20° without obvious threshold current increas. The results show that the mode expansion layers do not reduce the electrical properties and the temperature stability characteristics of lasers.