Amplification of discrete vector solitons by means of polarization instability

We study the dynamics of discrete vector solitons using the standard coupled-mode theory within the slowly-varying envelope approximation, but including four-wave mixing terms. First, we find approximate analytical solutions in the form of strongly localized vectorial modes. Next, we use these modes to find a closed expression for the average power transfer between the TE and the TM modes, as a function of their initial phase difference. We suggest a novel mechanism for achieving simultaneous switching and amplification (gain from 70% to 6000%) of a weak signal (TE) by a strong pump of the other polarization (TM) by means of a judicious choice of the pump input angle and the pump power.