Nondegenerate coherent control of polariton modes in a quantum-well semiconductor microcavity

We demonstrate nondegenerate coherent control of the cavity-polariton modes of a quantum-well semiconductor microcavity. Coherent excitation and de-excitation of one normal mode using a pair of phase-locked optical pulses gives rise to a nonlinear response on the other normal mode due to the nonlinearity of the exciton transition underlying the normal modes. The cavity enhancement of the excitonic nonlinearity gives rise to a large signal; modulating the relative phase of the excitation pulses between zero and π produces a differential reflectivity (ΔR/R) of up to 15%. Coherent control is used to measure the polariton dephasing time as a function of density. Excitation induced dephasing is shown to be the factor limiting the degree of coherent control.