DEGENERATE 4-WAVE-MIXING MEASUREMENTS ON AN EXCITON-PHOTON COUPLED SYSTEM IN A SEMICONDUCTOR MICROCAVITY

The polarization-sensitive degenerate four-wave mixing technique is em ployed to study semiconductor quantum-well microcavities in the low-de nsity Limit. Frequency-domain and time-domain measurements are carried out to study exciton-polariton modes in long- (high-Q)and short- (low -Q) photon lifetime systems. In the high-Q system, normal-mode splitti ng is observed in the linear reflection as well as the degenerate four wave mixing spectrum. Tn the low-e system, though the linear reflecti on spectrum shows normal-mode splitting, the spectrum of the degenerat e four-wave mixing is found to have a maximum only at the bare exciton resonance. Our experimental results are well reproduced by a weakly i nteracting boson model which accounts for the anharmonicity in the sys tem due to exciton-exciton correlation and the phase-space filling eff ect. The four-wave mixing results from the high-Q system are in good a greement with the cavity polariton scattering treatment for the third- order nonlinear response of the microcavity confined excitons. The pol arization sensitive frequency-domain degenerate four-wave-mixing measu rements from the high-Q system enable us to obtain the ratio of the an harmonic parameters, The frequency and time-domain measurements show t hat the strong coupling between the exciton and photon changes the non linear optical response qualitatively. Incoherent effects like the exc itation-induced dephasing are suppressed in the high-a system, whereas they are more pronounced in the low-e system. We also find difference s in the signal decay rates for different polarization configurations, which is attributed to inhomogeneous broadening in the low-e system. [S0163-1829(98)00236-7].