采用二维时域有限差分(FDTD)法，分析并对比了弯曲分叉部分的形状分别为正弦形和圆弧形的基于金属绝缘体金属（MIM）型表面等离子体光波导的Y形分束器的反射率、传输率以及能量分束比随几何结构参数的变化关系。数值计算表明，波导宽度对这两种Y形分束器传输特性的影响较为明显，两个输出分支的偏移量和弯曲分叉部分的长度对这两种Y形分束器传输特性的影响比较微弱。在600~1500 nm波长范围内，弯曲分叉部分为圆弧形的Y形分束器的传输特性比弯曲分叉部分为正弦形的好。对于非对称型Y形分束器，当弯曲分叉部分为正弦形时，偏移量对反射率、传输率和能量分束比的调节作用较为明显，能量分束比最大可达到2∶1。当弯曲分叉部分为圆弧形时，偏移量对反射率、传输率和能量分束比的调节作用较为微弱。

Using the two-dimesional finite-difference time-domain (FDTD) method, the dependence of the reflectivity, the transmission rate and the energy splitting ratio, on the geometrical parameters of two kinds of Y-splitter with sine shaped arc and circular shaped arc, based on mental-insulator-mental (MIM) surface plasmonic waveguides, are analysed. Results show that the transmission characteristics of the two Y-splitters depend obviously on the parameter of the width of the waveguides and weakly on the two parameters of the offsets of the two output branches and the lengths of the curves. The transmission characteristics of the Y-splitter whose curves are circular arc-shaped are better than the Y-splitter whose curves are sine arc-shaped within 600~1500 nm. For asymmetrical Y-splitter, the reflectivity, the transmission rate and the power splitting ratio are affected obviously by the parameter of offset when the curves are sine arc-shaped and the energy splitting ratio can be up to 2∶1. The reflectivity, the transmission rate and the power splitting ratio are affected faintly by the parameter of offset when the curves are circular arc-shaped.