Coherent control of parametric amplification in semiconductor microcavities

Summary form only given. Semiconductor microcavities containing quantum wells are ideal structures to investigate the coherent kinetics of interacting excitons and photons. At resonance between the exciton transition and an optical cavity mode, the polaritons are mixed exciton-photon states. The in-plane dispersion of the lower polariton branch has a particular shape, which permits to trap efficiently the polaritons in the states having wavevectors close to zero. Near the bottom of the dispersion curve, polaritons have very long dephasing times, due to the absence of energy and momentum conserving polariton-lattice scattering mechanisms. Parametric amplification involves polaritons of sufficient density that populate the states at the magic wavevector For these states, energy and momentum conserving polariton-polariton scattering mechanisms are possible. This parametric scattering can be stimulated by polaritons injected by a weak probe beam at normal incidence, and very high probe amplification can be achieved We demonstrate the coherent control of the parametric amplification process by shifting the relative phase of two probe pulses.