Far-field scattering of electromagnetic waves based on all-dielectric geometric phase encoding metasurfaces

Digital coding metasurfaces use binary digital states to represent the amplitude or phase of reflected or transmitted waves, and digitally characterize the electromagnetic properties of metasurfaces. To simplify the structure of the digitally encoded metasurface unit, we design a 3-bit geometric phase-encoded unit structure using the geometric phase principle. Based on the loss characteristics of metal materials, which seriously affect the device efficiency, we propose to use all-dielectric materials to construct an encoding unit, and then realize a terahertz wave all-dielectric geometric phase encoding metasurface. The coding metasurface can effectively control the far-field scattering angle of the incident wave. By arranging the coding units on the front surface according to different digital sequences, digital coding metasurfaces with corresponding different functions can be realized. However, based on the generalized Snell's law, the regulation of the scattering angle is limited by the period of the encoded structure. To obtain the free control of the scattering angle, we use the Fourier convolution principle in digital signal processing to perform addition and subtraction operations on different coding sequences to obtain the free control of the deflection of the abnormally scattered beam. At the same time, we also design a new checkerboard encoding metasurface that mixes gradient encoding and checkerboard encoding, which can simultaneously control four beams of anomalous scattered light.