Enhancement of Diffraction Efficiency Based on the Addition Principle of Coded Digital Gratings

For the traditional subwavelength gratings, we can code different units to construct the coded metagratings. In this paper, we propose an innovative principle of adding coded gratings, which can be used to add or subtract two or more traditional coded metagratings sequences and obtain a new coded metagratings sequence. Based on the proposed addition principle, the coded metagratings can adjust the scattering angle flexibly. This method overcomes the limitation that traditional grating can only obtain discrete diffraction angle. Importantly, compared with traditional gratings, the coded metagrating sequences with addition operation have enhanced diffraction efficiency at the same diffraction angle. This phenomenon may be attributed to the enhanced interaction between the coding particles of the new disordered coding sequence metagratings constructed or the impedance matching of interface. Our proposed coded grating addition principle provides a new degree of freedom for the flexible modulation of the terahertz wavefront. At the same time, this method can be extended to optical band or microwave band, which opens a new path for electromagnetic wave modulation and beam scanning.