Continuous scattering angle control of transmission terahertz wave by convolution manipulation of all-dielectric encoding metasurfaces

The digitally encoded metasurface provides flexible manipulation of the scattering properties of electromagnetic wave beams, and it can connect metasurface particles to digital codes to achieve unusual physical phenomena. At first, the research of coding metasurface mainly focused on the structural elements of metal materials. However, the ohmic loss of metal materials seriously affects the scattering efficiency of coding metasurface. To overcome ohmic loss, we propose to construct coded metasurface using all-dielectric element structure. Here, a complete 2 π transmitted phase with high efficiency can be controlled by cylindrical unit structures in terahertz frequency. Different coding sequences can control different transmission and scattering angles. However, these commonly coded metasurfaces cannot achieve continuous control of the scattering angle. In this study, Fourier convolution principle in digital signal processing is introduced through the four-bit operation of adding and subtracting two coding sequences to construct a new code sequence metasurface. The required coding pattern to flexible and continuous control scattering angle can be realized by the modulus of two encoding sequences. The Fourier convolution calculations of two gradient one-dimension encoding sequences and chessboard encoding sequences are implemented to realize the flexible control of single transmission beam and multiple beams. This fully digital perspective on the encoding metasurface can combine conventional digital signal processing with the encoding metasurface to achieve powerful manipulation of electromagnetic wave.