Dual-function polarization converter of an all-dielectric metasurface with a chiral L-type meta-atom

We propose a dual-function metasurface with a chiral double L-type silicon meta-atom that works in the near-infrared band. On one hand, the designed metasurface can achieve the function of a quarter-wave plate in the wavelength of 1660–1840 nm, and convert y -linear polarization (LP) light into right-hand circular polarization (RCP) light. The polarization conversion ratio (PCR) is above 90%, up to 98%, and the ellipticity of the transmitted light is 0.9–1.0. On the other hand, for a wavelength of 1497 nm, the designed structure can also convert LP in any direction to left-hand circular polarization (LCP) light by using the circular dichroism of chiral structures. The PCR is above 99%, and the ellipticity of the transmitted light is equal to approximately − 1 . Moreover, when incident in the opposite direction, the wave plate can convert LP to RCP light. At present, the all-dielectric metasurface has important application potential in polarization conversion and photonic integration.