Ultrafast tailoring of the exciton distribution in quantum wells

By excitation with two, consecutive, picosecond pulses we
demonstrate that the distribution and temperature of a photocreated
exciton population in semiconductor quantum wells
can be dynamically tailored. The changes in the exciton distribution
result in abrupt alterations of the photoluminescence
dynamics, in particular in the appearance of a sudden decrease
in the heavy-hole excitonic emission when the second pulse
impinges upon the sample. We present a quasi-equilibrium
thermodynamical model that includes the energy distribution
of excitons and electron–hole plasma, which quantitatively
accounts for the sharp dips observed in the exciton emission
dynamics.