INSERTION LOSS AND EXTINCTION RATIO OF A SURFACE PLASMON-POLARITON POLARIZER - THEORETICAL-ANALYSIS

A surface plasmon-polariton (SPP) polarizer with a shorter polarizer length can be realized by strong coupling of a metal film to a core, that is, by matching of the phase constant of the SPP wave in the metal film to that of the guided mode in the core and by selection of a suitably thin buffer-layer thickness. To calculate the polarizer's extinction ratio accurately, we have considered three TM supermodes of a SPP polarizer with a symmetric seven-layered slab structure rather than only a fundamental supermode that matches an input field well for large buffer thicknesses. When the buffer layer becomes thinner, the characteristics of the SPP polarizer cannot be simply estimated when only the propagation constant of the fundamental supermode is known, since its field distribution becomes quite different from that of the input field. It is shown that the field distribution beats in the SPP polarizer because of the interference effect of these supermodes. Finally, the total extinction ratio and insertion loss, including coupling losses at input and output ends, are estimated.