Polarization splitting in lossy/gainy MQW directional couplers

We analyze polarization splitting of light in directional-coupler polarizers by using a transverse modal transmission-line representation. Because it is based on rigorous modal solutions, this approach provides very accurate results and can be applied to situations involving either lossy or gainy materials. By considering a polarizer in which multiquantum-well layers act as one of the two waveguides forming the coupling region, we find that maximum polarization discrimination is achieved at an optimal distance that is different from the polarization length predicted by conventional coupled-mode methods. We derive a novel criterion for determining that optimal length, examine the effect of material loss or gain, and obtain the far-field intensity of the light at the output of the coupler.