Maximization of Extinction Ratios of Thin-Metal-Clad Optical Waveguide Polarizers with Proper Dielectric-Cover-Layer Thickness

We theoretically analyze the performance of optical thin-metal-clad waveguide polarizers with emphasis on the effect of dielectric-cover-layer (i.e., superstrate) thickness. We show that the polarization extinction ratio can be theoretically made infinite by selection of metal film thickness and polarizer length for a given dielectric-cover-layer thickness. It is shown that the required metal film thickness and polarizer length should be changed for reaching an infinite extinction ratio as different cover layer thicknesses are to be used. However, an infinite extinction ratio is not possible as the dielectric cover layer is thinner than some value. For fixed metal film and buffer layer thicknesses, a certain discrete cover layer thicknesses are required for reaching infinite extinction ratios.