Metal island film polarizer

Abstract

Many integrated optical devices are sensitive to the polarization of light. A thin film polarizer1,2 which transmits the transverse magnetic (TM) mode with a low insertion loss (<1 dB) and which attenuates the transverse electric (TE) mode with a high extinction ratio (>30 dB) is considered. The basic planar device structure consists of a dielectric waveguide which is separated from a parallel metal island film waveguide by a buffer region (Fig. 1). The difference between the TE and the TM modes arises due to the distribution of the metal islands in the film. Because of the excitation of the local surface plasmon in the metal particles, the attenuation of the TE mode is two orders of magitude greater than that of the TM mode. The physical parameters of the metal film waveguide are adjusted such that the TE mode is phase-matched with that of the TE mode of the dielectric waveguide. The TE mode of the optical waveguide is coupled distributively to the metal film waveguide and is attenuated, whereas the TM mode is not coupled due to significant phase mismatch and also is attenuated by two orders of magnitude less than that of the TE mode. Thus, an efficient TM mode pass on-line polarizer can be realized.