Nonlinear Optical Absorption Of Semiconductor Quantum Wires: Photoexcitation Dynamical Effects

We investigate the optical absorption spectra of semiconductor quantum wires and its dependence on the optical pumping power. The absorption coefficient is obtained solving the semiconductor Bloch equations in the real-space and time domains, including corrections due to band-gap renormalization, local field, and screening. We find that the energy shifts in the spectra due to increasing photoexcitation power have different behavior when treating dynamically the carrier creation rather than using stationary carrier distribution at thermal equilibrium. Dealing with the nonequilibrium distribution dynamically, we are able to describe the observed constancy of the peak position of the fundamental transition energy with the optical pumping power. The competing effects of the dynamical band-gap renormalization and the local-field correction leads to an almost cancellation of the red/blue shift energy.