Ultra-Thin Polarization Beam Splitter Using 2-D Transmissive Phase Gradient Metasurface

A new 2-D ultra-thin transmissive phase gradient metasurface (TPGM) with polarization-independent property is proposed based on the generalized Snell's law of refraction. The super unit cell of the tri-layer TPGM consists of $6 \times 6$ suitably selected elements with $- {60}^\circ $ phase gradient at $x $-direction and 60° phase gradient at $y $-direction, respectively. The characterizations and working mechanisms of the TPGM are investigated in depth through theoretical calculation, comparative analysis, and electromagnetic (EM) simulation. Four types of TPGMs with different functionalities are proposed based on the derived four-step design method. Numerical results show that the TPGMs are capable of manipulating the differently polarized wave independently. For demonstration and potential applications, an ultra-thin polarization beam splitter (PBS) working at X-band is implemented by a specially designed 2-D TPGM and is launched by a wideband horn antenna from the perspective of high integration, simple structure, and low cost. Numerical and experimental results coincide well, indicating that the PBS advances in many aspects such as separating and controlling the orthogonally polarized waves with a polarized splitting ratio better than 18 dB, obtaining a comparable bandwidth of more than 600 MHz, gaining a high transmission efficiency and also adopting a simple fabrication process based on the convenient print circuit board (PCB) technology.