Beam-Editing Coding Metasurfaces Based on Polarization Bit and Orbital-Angular-Momentum-Mode Bit

Coding metasurfaces are aimed at representing digital information of the metasurface, usually by programing digital unit cells to control electromagnetic waves. However, some information sequences cannot be recognized by the receiver, because of nonorthogonality of the usual phase codes. Here, new coding method is proposed to encode information with orthogonal parameters in the emitting beam, which reduces information loss in the system. A vector beam modulator is proposed by combining orthogonal polarizations and orbital angular momentum (OAM) modes. A normal incident wave can be modulated by OAM-mode bit and polarization bit, which are regarded as specific information by the receiver. A polarization converter is used to realize the polarization selection (polarization bit) and phase control, independently. The phase patterns on the coding metasurfaces can be programed to realize the designed OAM modes (OAM bits) in the microwave frequency. Three schemes are presented to emit multiple OAM modes in dual polarizations, one of which is manufactured and measured for near and far fields. The simulations and experiments are in outstanding agreement, verifying the excellent performance of the proposed schemes. This work has great potential in communication applications of coding metasurfaces.