GAIN SPECTROSCOPY OF EXCITONIC MOLECULES AND ITS DYNAMICS IN A ZNSE SINGLE-QUANTUM-WELL

We demonstrate spectroscopically how optical gain is formed in an inte racting system of excitons and biexcitons in a single ZnSe quantum wel l. The dynamics of gain formation are studied on a subpicosecond time scale in pump-probe experiments, revealing the influence of coherent e ffects and the impact of exciton-exciton and exciton-biexciton interac tions. Spectrally resolved, polarization-dependent degenerate four-wav e-mixing experiments further demonstrate how the excitonic many-body p henomena profoundly influence the nonlinear optical response in this I I-VI semiconductor heterostructure.