Crossover from exciton to biexciton polaritons in semiconductor microcavities

Pump-probe measurements in a microcavity containing a quantum well show tha t a population of circularly polarized (sigma(+)) excitons can completely i nhibit the transition to sigma(-) one-exciton states by transferring the os cillator strength to the biexcitonic resonance. With increasing pump intens ity the linear exciton-polariton doublet evolves into a triplet polariton s tructure and finally into a shifted biexciton-polariton doublet. A theoreti cal model of interacting excitons demonstrates that the crossover from exci ton to biexciton polaritons is driven by three-exciton Coulomb correlation.