Applied Sciences, Vol. 12, Pages 12322: Grating-like Terahertz Metasurface for Large-Deflection-Angle Beam Manipulations

Figure 1. Schematic configuration of the metasurface grating. The geometric parameters of the unit cell are as follows: a = 160 μm, b = 40 μm, c = 6 μm, g = 16 μm, w = 16 μm, Dx = 400 μm, and Dy = 200 μm. The metasurface consists of seven layers, which from top to bottom, are quartz, complementary split-ring resonator (CSRR), Polyimide (PI), liquid crystal (LC), PI, metal ground, and silicon substrate. The thickness of the metal layer (gold), PI, and LC are 300 nm, 90 nm, and 45 μm, respectively. Silicon substrate and ultrathin quartz (which are not shown in the schematic) are used to support the metal ground and metallic CSRR, respectively, and PI layers engineered with parallel grooves are contributed to the pre-orientation of liquid crystal molecules.

Figure 1. Schematic configuration of the metasurface grating. The geometric parameters of the unit cell are as follows: a = 160 μm, b = 40 μm, c = 6 μm, g = 16 μm, w = 16 μm, Dx = 400 μm, and Dy = 200 μm. The metasurface consists of seven layers, which from top to bottom, are quartz, complementary split-ring resonator (CSRR), Polyimide (PI), liquid crystal (LC), PI, metal ground, and silicon substrate. The thickness of the metal layer (gold), PI, and LC are 300 nm, 90 nm, and 45 μm, respectively. Silicon substrate and ultrathin quartz (which are not shown in the schematic) are used to support the metal ground and metallic CSRR, respectively, and PI layers engineered with parallel grooves are contributed to the pre-orientation of liquid crystal molecules.

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Figure 2. The far-field radiation patterns for (a,b) CSRR-based metasurface grating and (c,d) metallic strip-based grating at 0.87 THz. (a,c) 3D far-field patterns; (b,d) 1D far-field patterns. In simulation, both the two 1D gratings have 16 lines.

Figure 2. The far-field radiation patterns for (a,b) CSRR-based metasurface grating and (c,d) metallic strip-based grating at 0.87 THz. (a,c) 3D far-field patterns; (b,d) 1D far-field patterns. In simulation, both the two 1D gratings have 16 lines.

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Figure 3. (a) The optical micrograph of the fabricated metasurface grating; the measured results of the diffraction wave. (b) +1st order mode; (c) −1st order mode.

Figure 3. (a) The optical micrograph of the fabricated metasurface grating; the measured results of the diffraction wave. (b) +1st order mode; (c) −1st order mode.

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Figure 4. The measured results of the diffraction wave (+1st order mode) compared with the theoretical and simulated results.

Figure 4. The measured results of the diffraction wave (+1st order mode) compared with the theoretical and simulated results.

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Table 1. Diffraction angles calculated at different incident wave frequencies.

Table 1. Diffraction angles calculated at different incident wave frequencies.

Incident Frequency/THzDiffraction Angle/DegreeIncident Frequency/THzDiffraction Angle/Degree0.87±59.50.95±52.10.88±58.50.96±51.40.89±57.40.97±50.60.90±56.40.98±49.90.91±55.50.99±49.30.92±54.61.00±48.60.93±53.81.01±48.00.94±52.91.02±47.3

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