Polarization rotation with ultra-thin bianisotropic metasurfaces

Controlling the polarization of light with efficient and ultra-thin devices is desirable for a myriad of optical systems. Bianisotropic metasurfaces offer a promising alternative to conventional optical components due to their ability to provide extreme wavefront and polarization control within a low profile. However, metasurfaces have typically suffered from poor efficiencies and extinction ratios due to the lack of systematic design procedures. Here, the first, to the best of our knowledge, impedance-matched polarization rotator with a subwavelength thickness that operates at optical frequencies is reported. The bianisotropic response needed for polarization rotation is systematically designed using cascaded plasmonic sheets. The metasurface is fabricated using straightforward nanolithography processes. Measurements demonstrate an efficiency of 45% and extinction ratio of 115 (20.6 dB) at the operating wavelength of 1.56 μm. This work experimentally demonstrates that a wide range of near-optimal bianisotropic responses can be designed and fabricated at optical frequencies. In the future, these surfaces could be utilized to develop high-performance, ultra-compact optical systems.