Single-Row Coding Metasurface for Bi-directional Beam Multiplexing in Mid-infrared Regime

Through selecting several discrete coding elements (i.e., bit) and arranging them in predefined configurations, coding metasurface allows the programming of different functions by efficiently engineering the photons in dimensions like phase, magnitude, and polarization. However, simultaneously manipulating electromagnetic waves in both vertical and lateral directions, which provides an unconventional degree of freedom to multiplex the controlling channels and enables additional functions in one single metasurface, is hardly reported. Here, we propose a single-row coding metasurface to simultaneously control electromagnetic waves in both vertical and lateral directions in mid-infrared regime. For a proof of concept, the 3-bit coding sequence for addition and subtraction operations at 4 μm is respectively adopted for beam deflection demonstration. The simulated results are in good agreement with the theoretical expectations. Besides, the encoded beam focusing with this one row metasurface is realized with diffraction-limited spots for both directions. Remarkably, two-channel beam splitters multiplexed at two distinct wavelengths for both directions are also achieved through alternatively implementing the 1-bit metaatoms. Great consistency between simulation and analytical results is observed. We believe the proposed single-row coding metasurface has the potential to push the development of optical communication, signal processing, and imaging devices in optics.