Electrically controlled beam steering with wide deflection angles in liquid crystal photonic crystals

Electrically controlled beam steering behaviors in a 2D square photonic crystal (PC) composed of Si cylinders surrounded by nematic liquid crystal are studied. The results show that by applying an external saturated electric field, the structure becomes anisotropic and results in remarkable change of band structure to produce a single band from 0.3105 to 0.3245(c/a) accordingly. This special single band is high anisotropic and only allows one mode with negative refraction to be excited in the Gamma M direction. Further studies show that as the external saturated electric field rotates from 0 degrees to 90 degrees, the equifrequency contours of the single band deform continuously from rectangle-like to parallelogram-like shapes, and then recover to rectangle-like shapes but with the long-side rotated by 90 degrees. Moreover, we demonstrate continuous tunable beam steering behaviors with wide deflection angles from -38 degrees to +38 degrees at normal incidence by finite-difference time-domain simulations. These results have the potential for designing various tunable PC devices.