  We report on the temporal lasing dynamics of high quality ZnO nanowires using
time-resolved micro-photoluminescence technique. The temperature dependence of
the lasing characteristics and of the corresponding decay constants demonstrate
the formation of an electron-hole plasma to be the underlying gain mechanism in
the considered temperature range from 10 K to 300 K. We found that the
temperature dependent emission onset-time ($t_{\text{on}}$) strongly depends on
the excitation power and becomes smallest in the lasing regime, with values
below 5 ps. Furthermore, the observed red shift of the dominating lasing modes
in time is qualitatively discussed in terms of the carrier density induced
change of the refractive index dispersion after the excitation laser pulse.
This theory is supported by extending an existing model for the calculation of
the carrier density dependent complex refractive index for different
temperatures. This model coincides with the experimental observations and
reliably describes the evolution of the refractive index after the excitation
laser pulse.
