Dual-polarization programmable metasurface modulator for near-field information encoding and transmission

Controlling the polarization state of electromagnetic waves is an important topic in microwaves due to the enormous application potential in radar technology and mobile communications. Here, we propose a programmable metasurface based on single-pole double-throw switches to realize multifunctional polarization conversions. A structure of the double-sided metallic pattern is adopted in the metasurface, in which a novel double-pole double-throw hub is achieved to guide the energy direction. Such a mechanism successfully induces multiple transmission channels into the metasurface structure for functional design. By controlling the states of the switches with a field programmable gate array, the x - and y -polarizations of the incident waves can be efficiently modulated into linear co- and cross-polarizations of transmitted waves, suggesting a higher degree of freedom on wave manipulations. The proposed metasurface can be developed as a near-field information encoder to transmit binary coding sequence according to the energy distribution. Character transmissions are realized by programming binary ASCII codes on the transmitted fields. Nine supercells on the metasurface can encode 9-bit binary information in one frame of near-field imaging, which can be switched in real time with high speed. We envision that this work will develop digital coding applications to control the polarization information.