we proposed a mode splitter based on directional coupler (dc), which is capable of splitting the te0 and te1 modes without changing the mode order. it is found that high coupling efficiency (higher than -1 db), low mode crosstalk (less than -16 db), wide bandwidth (similar to 100 nm), and large fabrication tolerance (+/- 10 nm) can be obtained by a 24.4 mu m coupling length dc structure, which is composed of a strip and a slot silicon waveguide. this design represents a first step toward mode splitter without changing the mode order, which can find important potential applications, such as optical isolation and mode division multiplexing (mdm), in large-scale photonic integrated circuits (pics).