Flexible control of transmitting terahertz beams based on multilayer encoding metasurfaces

The concept of encoding metasurfaces makes a connection between the physical metamaterial particles and the digital code so the digital coding can be performed on the coding surface for signal processing to achieve unusual physical phenomena. Here, a complete 2π transmission phase with high efficiency at the target frequency can be manipulated by a multilayer metasurface structure. Different period sequence codes are designed to obtain the deflection angles, and then a new sequence is obtained through a four-bit system operation sequence according to the Fourier convolution principle. This study shows that Fourier calculation provides an efficient way to optimize the coding to achieve a pre-designed transmitted beam. The advantage of this method over previous solutions in generating an anomalous single transmission beam is its flexibility and continuous control of arbitrary directions, and it is possible to transmit a normally incident terahertz beam to an abnormal arbitrary direction with cross-polarization. This work opens up a new digital perspective on the new approach to metamaterials, predicting the possibility of combining electromagnetic wave operations with the convolution theorems in digital signal processing and the transcoding surface.