Polarization dynamics induced by the "virtual excitation" of spin-polarized carriers: applications to all-optical polarization switching

Summary from only given. Recently we have demonstrated an optically-addressed coherent polarization switch that is based on the near-resonant excitation of a spin-polarized population of virtual excitons in MQWs. By taking advantage of the nonlinearities associated with a virtual carrier population, this near resonant device exhibits a pulse-width-limited response; by operating near resonance it is capable of producing relatively large contrast ratios in thin samples; and finally, by generating a spin-polarized carrier population, the device produces a rotation of the signal polarization in unstrained MQWs. Here, we experimentally analyze the switching mechanisms by systematically performing spectrally and temporally resolved differential transmission measurements and by fully determining the polarization state of the transmitted signal as a function of time delay.