Stimulated spin scattering in semiconductor microcavities

Summary form only given. We show that the ultra-nonlinear response which arises from the parametric scattering of pairs of polaritons, possesses a strong and unusual dependence on the spin of the polaritons. Previously we showed that the polariton spin (up or down) is well-defined and uniquely accessed by the particular circular polarisation (right or left respectively) of the excitation lasers. By developing time-resolved spectroscopies that measure the gain of a probe pulse along three independent polarisation axes (horizontal or vertical linear, diagonal crossed linear, and right or left circular), we completely specify the polarisation of the microcavity emission for the first time.