Angular-asymmetric nonlinear polariton dynamics in semiconductor microcavities

Parametric interactions in semiconductor heterostructures in which two exci ton quasiparticles mutually scatter are typically weak because they are res tricted by energy-momentum conservation. Here, semiconductor microcavities in the strong coupling regime are optically pumped at specific resonant ene rgy and angle of incidence to enormously enhance the parametric interaction s. A femtosecond goniometer is devised to allow time-, wavelength- and pola risation-resolved pump-probe spectroscopy. Time-resolved images of the micr ocavity emission at different angles reveal a highly asymmetric luminescenc e distribution which switches on as the pump power is increased. Both signa l and idler beams can be identified when a probe purse initiates stimulated scattering of polaritons from a reservoir. The images show the rich variet y of interactions produced by the coupling of light-matter modes, and the f uture promise of dispersion engineering.