All‐Silicon Diatomic Terahertz Metasurface with Tailorable Linear Polarization States

Abstract Polarization plays a key role in fundamental science, and the improvement in miniaturization and practicability of polarization conversion devices could provide more degrees of freedom for light–matter interactions. Metasurfaces that can manipulate arbitrary polarization states at subwavelength scales can significantly reduce the complexity of meta‐optical systems. Here, a general design of an all‐silicon diatomic metasurface operating in the terahertz band that can generate a tailorable linear polarization state by the superposition of two meta‐atoms with individual geometric parameters is experimentally demonstrated. By periodically arranging polarization‐converting and polarization‐maintaining meta‐atoms, the existence of interference effects enables the proposed diatomic meta‐platform to act as an optimal linear polarization operator. The gradient arrangement of the meta‐molecules under the profile of the propagation phase is deduced by using the advanced Jones matrix, so that the polarization filtering and wavefront manipulation can be realized simultaneously, including the generation of tightly converged vortex and bifocal focusing beams. This demonstration of generating tailorable linear polarization states located on the Poincaré sphere directly from arbitrarily polarized waves can significantly facilitate the development of functional polarization meta‐devices.