Effects of propagation on the population dynamics of terahertz quantum cascade lasers

摘要

The spatial and temporal dependence of population dynamics caused by ultrafast a laser pulses are studied by Maxwell-Bloch equations in terahertz quantum cascade lasers with and without propagation effects. It is shown that the presence of propagation effects could decrease the flopping of population inversion and affect the oscillation intensity in recovery process. Due to the modification of total macroscopic nonlinear polarization and many-body items, local field varies not only with electron doping concentration but also with period position, which also reflected in the evolution of population dynamics.