Design and analysis of multi-angle diffraction efficiency distribution for all-dielectric transmissive grating

This paper presents the design of a C-shaped all-dielectric metasurface. The C-shaped dielectric structure and its substrate materials are Si and SiO<sub>2</sub>, respectively. This unit structure enables independent control of the amplitude and phase of cross-polarized transmitted terahertz electromagnetic waves. By using parameter scanning method, four different unit structures were optimized at 0.1 and 1 THz, achieving unit phase distributions with a 45° interval within the range of 0° to 180°. Additionally, a 180° phase jump occurs when the unit structure rotates by 90°, achieving full phase control over the 360° range. By adjusting the orientation of the unit structure, arbitrary amplitude control can also be achieved. The highest transmission coefficients for the unit structures at 0.1 and 1 THz are 0.62 and 0.56, respectively. To verify the control capability of the designed unit structure on transmitted electromagnetic waves, metasurface gratings were designed based on these unit structures, enabling arbitrary control of diffraction angles and orders. At both frequencies, two different metasurface gratings were designed with diffraction orders of (<i>m</i> = +1) and (<i>m</i> = +1, +3). Near-field and far-field simulations of the super-grating structures were conducted using the finite integral method. The designed metasurface grating demonstrates effective control of cross-polarized transmitted waves, and its deflection angles conform to diffraction laws.