Liquid-crystal blazed grating with spatially distributed four-level twisted nematic domains

A liquid crystal (LC) cell with multiple twisted nematic domains is fabricated by rubbing alignment films along different directions and is applied to an LC four-level blazed grating. It is theoretically derived that the four-level stepwise phase profile is achieved under optimum LC molecular orientation conditions. The LC four-level blazed grating is obtained by microrubbing using a tiny stylus with a curvature radius of 25 mum. The electrically controllable diffraction efficiency and unique polarization-splitting properties are revealed; namely, the diffraction efficiency can reach approximately 0.8 and the polarization directions of +/-1st-order diffractions are orthogonal to each other.