Large-signal coherent control of normal modes in quantum-well semiconductor microcavity

We demonstrate coherent control of the cavity-polariton modes of a quantum- well semiconductor microcavity in a two-color scheme. The cavity enhancemen t of the excitonic nonlinearity gives rise to a large signal; modulating th e relative phase of the excitation pulses between zero and pi produces a di fferential reflectivity (DeltaR/R) of up to 20%. The maximum nonlinear sign al is obtained for cocircular pump and probe polarization. Excitation-induc ed dephasing is responsible for the incoherent nonlinear response, and limi ts the contrast ratio of the optical switching. (C) 2001 American Institute of Physics.