The temporal evolution of an electron in a double rectangular quantum dot in the presence of an electric field pulse is explored in this work. In the framework of the effective mass approximation, first-order scattering rates for electron–electron and electron–longitudinal acoustic phonon interaction at room temperature are calculated in the high tunnelling regime, and used to evaluate the dynamics of the population and coherence of the first three confined levels under an electric field pulse. Small values of these rates dependent upon the coupling barrier make feasible the emission of coherent radiation near 0.1 THz.