%0 Journal Article
%T A TM-Pass/TE-Stop Polarizer Based on a Surface Plasmon Resonance
%A Yuu Wakabayashi
%A Junji Yamauchi
%A Hisamatsu Nakano
%J Advances in OptoElectronics
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/867271
%X A TM-pass/TE-stop polarizer consisting of a metal film sandwiched between dielectric gratings is investigated using the finite-difference time-domain method. At normal incidence with respect to the grating plane, a transmissivity of more than 94% and a reflectivity of more than 98% are obtained at £¿ m for the TM and TE waves, respectively. The extinction ratio is more than 17£¿dB over a wavelength range of 1.50£¿ m to 1.75£¿ m. A high extinction ratio is maintained at oblique incidence, although the wavelength range shifts towards longer wavelengths. The TM-pass/TE-stop operation is also achieved with a modified structure, in which a dielectric grating is sandwiched between metal films. 1. Introduction There are a great number of papers devoted to the study of light propagation in periodic structures [1]. One of the important applications of the periodic structures is to construct a polarizer, which is used in optical communications and sensing devices. Recently, high transmission of the transverse magnetic (TM) wave through a thin metal film has been suggested and discussed [2¨C4]. The transmission is closely related to a surface plasmon (SP) resonance [5]. The SP resonance is realized using a thin metal film sandwiched between dielectric gratings. We should also note that recent interest has been directed toward plasmon waveguides operating at (optical communication band) [6, 7]. In this paper, the SP-based enhanced transmission through a thin metal film is investigated in more detail in the optical communication band. The finite-difference time-domain (FDTD) method is used for the analysis. To obtain a high transmissivity for the TM wave and a high reflectivity for the transverse electric (TE) wave with a subsequent high extinction ratio (ER), we appropriately choose the width and thickness of the dielectric grating. In addition to normal incidence with respect to the grating plane, we consider the case of oblique incidence. It was found that the wavelength range, in which the high ER is observed, shifts towards longer wavelengths. To alleviate the fabrication difficulty, we also deal with a modified structure, in which a dielectric grating is sandwiched between metal films. The TM-pass/TE-stop operation is achieved at£¿£¿ , although the transmissivity is low compared with that obtained from the original structure. 2. Configuration and Numerical Method Figure 1 illustrates the periodic structure of the polarizer, in which a two-dimensional model is treated. The configuration is similar to that treated in [2, 3]. We illuminate a uniform plane wave of either
%U http://www.hindawi.com/journals/aoe/2011/867271/