中文摘要：

最近人们[1-3]提出了一类反射式梯度特异材料表面系统,此系统可以高效地将入射波转换成被束缚于材料表面的表面波,这个系统成为连接行波和表面波的一座桥梁。以往人们研究梯度特异材料表面的反射特性时多是以入射平面波为主,这里我们结合实际,以入射的高斯光束作为研究对象,讨论梯度特异材料表面对其的反射特性,尤其是高斯光束的主入射角和束腰对反射行为的影响,得到了与平面波入射不同的反射现象。对于临界角为17.2°的梯度特异材料表面,束腰为4的高斯光束以主入射角分别为0°、10°、30°入射时,我们发现随着主入射角的变大,入射高斯光束转变为表面波的比例增大;而固定主入射角为30°,我们通过改变束腰,发现束腰越大,波矢分布越窄,越接近于平面波,转变为表面波的效率就越高。在数值模拟中,反射光束出现了明显的Goos-Hansen位移现象。同时还出现了类似光栅反射的特点,即分叉现象,这是由于模拟计算时网格不能无限小,梯度特异材料表面不能模拟为折射率连续变化的材料而应该是阶跃式变化的材料。由于实际制备的梯度特异材料表面是人工微结构的排列,因此微小的阶跃式变化的梯度特异材料表面更为实际。我们的工作对于利用梯度特异材料表面将入射高斯光束转变为表面波具有指导意义。

英文摘要：

Gradient meta-surface,as a bridge to connect travelling wave and surface wave,has been designed recently in order to efficiently convert incident propagating wave into surface wave.Previously,the reflective properties of gradient meta-surfaces people have been studied based on plane wave.Here we focus on the incident Gauss beam and show the influence of incident angle and waist of Gauss beam on the conversion efficient of gradient meta-surface.For the gradient meta-surfaces with critical angle 17.2°and the Gauss beam with 4 times of wavelength waist,we find that the conversion efficiency from propagating wave into surface wave increases with the incident angle when it changes from 0 to 30°.Meanwhile,when the incident angle is fixed at 30°,we find the conversion efficiency also increases with beam waist,because larger waist means narrower wave vector distribution,and more component of beam can be transferred into surface wave.In the numerical simulation,obvious Goos-Hansen shift is observed.Furthermore,there are some bifurcations of reflective beam under certain conditions due to the result of interference and the finite grid in simulation.However the finite grid is corresponding to the experiment cases which the gradient meta-surfaces can not be manufactured into step type change.Our work is helpful for the further metasurface research.