单向激发表面等离子体，在光通信、集成光学、光刻等方面有着广泛的应用。从理论上提出了一种亚波长金属狭缝凹槽结构，利用背照射的激发方式，在金属膜表面实现了单向激发表面等离子体。设计过程中采用时域有限差分法进行数值模拟。首先改变凹槽的深度和宽度使得通过凹槽传播的表面等离子体的电场强度达到最低，并利用散射矩阵理论解释了其物理机制。然后基于表面等离子体干涉原理，改变狭缝与凹槽之间的距离使向背离凹槽一边传播的表面等离子体干涉加强，从而使金属狭缝-凹槽结构实现单向激发表面等离子体，最大分束比可以达到8。

Unidirectional excitation of surface plasmon polaritons has been applied widely in optical communication, integrated optics, lithography and so on. A subwavelength structure of metallic slit-groove in theory is proposed. This structure achieves unidirectional excitation of surface plasmon polaritons along the metallic film under back illumination. During our design, finite-difference time-domain method (FDTD) is adopted for numerical simulation. At first, the electric field intensity of surface plasmon polaritons which transmits through the groove can reach minimum by changing the depth and width of the groove, and the physical mechanism can be explained with the scattering matrix theory very well. Then based on surface plasmons′ interference principle, the interference of surface plasmon polaritons, which propagate along the side deviating from the groove, can be strengthened by changing the distance between the slit and groove. Thereby, the metallic slit-groove structure realizes unidirectional excitation of surface plasmon polaritons. The maximum splitting ratio can reach up to 8.