Ultra-broadband polarization metasurface-based splitter with tunable beam splitting ratio

Abstract

The metal–insulator–metal trapezoidal 2π phase metasurface is popular for its advantages of easy fabrication, large deflection angle range and a relative broad waveband under normal incidence that parallel to the short side. However, at the wavelength where exists 2nd-order diffraction, there has low 1st-order diffraction conversion efficiency, and the structure does not have the ability of polarization dependent beam manipulation. Our work is to perfect the phase distribution by placing another trapezoid orthogonally next to the original trapezoid, suppress the 0-order and 2nd-order diffractions. The +1st (-1st)-order is mainly controlled by x- (y-) polarized incidence, by rotating the polarization direction of the incident light, we design a tunable beam splitter with a wide range of splitting ratios by numerical simulation. In most wavelengths of 1000–2500 nm, an equal-power beam splitter can be realized.