Efficient manipulation of terahertz waves by multi-bit coding metasurfaces and further applications of such metasurfaces

Benefiting from the unprecedented superiority of coding metasurfaces at manipulating electromagnetic waves in the microwave band, in this paper, we use the Pancharatnam-Berry (PB) phase concept to propose a high-efficiency reflective-type coding metasurface that can arbitrarily manipulate the scattering pattern of terahertz waves and implement many novel functionalities. By optimizing the coding sequences, we demonstrate that the designed 1-, 2-, and 3-bit coding metasurfaces with specific coding sequences have the strong ability to control reflected terahertz waves. The two proposed 1-bit coding metasurfaces demonstrate that the reflected terahertz beam can be redirected and arbitrarily controlled. For normally incident x-and y-polarized waves, a 10 dB radar cross-section (RCS) reduction can be achieved from 2.1 THz to 5.2 THz using the designed 2-bit coding metasurface. Moreover, two kinds of orbital angular momentum (OAM) vortex beams with different moduli are generated by a coding metasurface using different coding sequences. Our research provides a new degree of freedom for the sophisticated manipulation of terahertz waves, and contributes to the development of metasurfaces towards practical applications.