Fig. 1. Schematic of the unit cell structure.单元结构示意图

Fig. 2. Transmission characteristic of the unit cells with different rotation angle of double-split resonant rings under the left circularly polarized incidence: (a) Transmission coefficients of the cross-polarized component; (b) phase shift of the cross-polarized component.在左旋圆偏振波入射下不同旋转角度双开口谐振环单元结构的太赫兹透射特性模拟结果　(a)交叉偏振分量的透射系数; (b)交叉偏振分量的相位改变

Fig. 3. Schematic of two different designed metasurface for generating vortex beams with topological charges of (a) l = 1 and (b) l = 2 两种用于产生拓扑荷数分别为　(a) l = 1和(b) l = 2的涡旋光束超表面

Fig. 4. Distributions of the amplitude and phase of the two metasurfaces for generating vortex beams with topological charges of 1 and 2 at 1.7 THz: (a) Amplitude and (b) phase distributions at the plane of z = –500 µm for l = 1; (c) amplitude and (d) phase distributions at the plane of z = –1000 µm for l = 1; (e) amplitude and (f) phase distributions at the plane of z = –500 µm for l = 2; (g) amplitude and (h) phase distributions at the plane of z = –1000 µm for l = 2. 通过超表面产生拓扑荷数为1和2的涡旋光束的振幅和相位分布. 对于l = 1, 在z = –500 µm平面处的(a)振幅和(b)相位分布. 对于 l = 1, 在z = –1000 µm平面处的(c)振幅和(d)相位分布. 对于 l = 2, 在z = –500 µm平面处的(e)振幅和(f)相位分布. 对于 l = 2, 在z = –1000 µm平面处的(g)振幅和(h)相位分布

Fig. 5. Distributions of the amplitude and phase of metasurface for generating vortex beam with topological charge of 1: (a) Amplitude and (b) phase distributions at the plane of z = –500 µm for l = 1 at 1.4 THz; (c) amplitude and (d) phase distributions at the plane of z = –500 µm for l = 1 at 1.9 THz. 超表面产生拓扑荷数为1的涡旋光束的振幅和相位分布. 在1.4 THz下, 对于l = 1, 在z = –500 µm平面处的(a)振幅和(b)相位分布; 在1.9 THz下, 对于 l = 1, 在z = –500 µm平面处的(c)振幅和(d)相位分布

Table 1. Optimized parameters of structure based on the double-split resonant rings.