设计了一种结构渐变的表面等离子体光栅光吸收器，采用二维时域有限差分法（2D-FDTD）对其吸收特性进行了详细的分析。结果表明，通过调整槽深、槽宽和墙宽，可以有效地降低反射率，提高其对光的吸收能力。由中心向两边适当地使槽宽线性增加，同时使墙宽线性减小，可以达到较理想的吸收效果。对于不同空间半峰全宽的入射光，反射谱线的形状有所不同。当入射光的空间半峰全宽较窄时，该吸收器对短波长光的吸收能力更强。当入射光的空间半峰全宽较宽时，该吸收器对长波长光的吸收能力更强。这种光吸收器有望在全光芯片中得到应用。

A kind of surface plasmonic grating optical absorber with gradually varying geometrical parameters is designed, and its absorption characteristics are analyzed in detail by the two-dimensional finite-difference time-domain (2D-FDTD) method. Results show that the reflectivity can be effectively reduced and the absorption capacity can be enhanced by adjusting the depths of the grooves, the widths of the grooves and the thicknesses of the walls. By increasing the widths of the grooves linearly and reducing the thicknesses of the walls linearly from centre to the both sides at the same time, better absorption effect can be achieved. The shape of the reflection spectrum is different for different spatial full width at half-maximum of the incident light. When the full width at half-maximum is narrow, the absorption ability is stronger for shorter wavelength light. When the full width at half-maximum is wide, the absorption ability is stronger for longer wavelength light. This light absorber is expected to be applied in all-optical chips.