Mid-infrared polarization devices based on the double-phase modulating dielectric metasurface

Metasurfaces are composed of the subwavelength structures, which can be used to manipulate the phase, amplitude and polarization of transmitted or reflected electromagnetic waves. Here, we propose an all-dielectric metasurface working in mid-infrared (mid-IR) range, in which the transmitted phase can almost span over the entire 2π range for both X-polarization and Y-polarization simultaneously just by tailoring the geometric sizes of the silicon (Si) nanobricks, while the transmitted amplitude can be maintained at high values without significant variations. We have successfully realized the beam deflector, beam splitter and the focusing lenses based on the designed metasurfaces at a wavelength of 4.5 µm. Our work paves the way toward establishing low-loss dielectric-based mid-IR devices and extends the modulating dimension of the metasurfaces.