Liquid-Crystal Blazed grating with Spatially Distributed Four-Level Twisted Nematic Domains

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Abstract
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 µm. 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.