Nonlinear dynamics of the exciton reflection spectrum

Nonlinear dynamics of reflection from InGaAs/GaAs quantum well was studied by pump-probe spectroscopy. Brewster geometry allowed to extract the time dependency of radiative width and nonradiative broadening of the excitonic resonance from reflection spectra. Pump pulse action leads to the increase of the nonradiative broadening and decrase of the radiative width. Fast decay component of the additional nonradiative broadening is attributed to the scattering on the pump-induced excitons. Slow component was explained by a scattering either on pump-induced charged carriers, or subsequently formed trions. This assumtion is additionaly proved by the decrease of the radiative width with same decay times caused by the redistribution of oscillator strength between exciton and trion states. (paper)