Low-reflective wire-grid polarizers with absorptive interference overlayers

Abstract

Wire-grid (WG) polarizers with low reflectivity for visible light have been successfullydeveloped. We theoretically consider the optical properties of simple sandwich structures ofabsorptive layer/transparent layer (gap layer)/high-reflective mirrors and found that it ispossible to develop an antireflection (AR) coating owing to the interference along with theabsorption in the absorptive layer. A wide variety of materials can be used for ARcoatings by tuning the thicknesses of both the absorptive and the gap layers. ThisAR concept has been applied to reduce the reflectance of WG polarizers of Al.FeSi2 as an absorptive layer has been deposited by the glancing angle depositiontechnique immediately on the top of Al wires covered with a thinSiO2 layer as a gap layer. For the optimum combination of the thicknesses ofFeSi2 andSiO2, the reflectance becomes lower than a few per cent, independent of the polarization,whereas the transmission polarization properties remain good. Because low-reflective (LR)WG polarizers are completely composed of inorganic materials, they are useful forapplications requiring high-temperature durability such as liquid crystal projectiondisplays.