Liquid-crystal metasurfaces for active polarization control

We present active control in two dimensions (2D) of the polarization of near infrared light in transmission using liquid crystal (LC) infiltrated TiO2 nanostructures with > 50% efficiency in experiment. Our device consists of a periodic subwavelength array of elliptical TiO2 nanopillars submerged in a thin (~ 2 μm) LC layer and supports overlapping electric and magnetic dipoles under linearly polarized incidence. Using a biased photoactive top contact, we control the polarization of transmitted light in 2D by patterning a 435 nm pump laser on the surface of the device to locally rotate LCs only in the illuminated areas. This work can find applications in solid-state programmable beam shaping and steering.