Study of dynamical dipole moment in an asymmetric double quantum well

Abstract

A study of the dynamical behavior of the charge in an asymmetric double quantum well is presented. In particular, the time behavior of intrasub-band dipole moment which is induced by intersub-band optical excitation is analyzed in two aspects: first, design of the quantum wells in order to spatially separate the charge and store it and second study the dynamic tunneling effect between the two wells. Since both conduction band levels are optically populated by transitions from a single band level, they are coherently coupled. The intrasub-band density matrix completely characterizes the dynamics of the conduction band electrons. These dipole moment oscillations are entirely equivalent to the tunneling oscillations between the two wells. The time dependent dipole moment produced by these real-space charge oscillations is obtained as a source of dipole electromagnetic radiation in THz region, which has been detected experimentally. The calculations show the geometry dependence of the emitted radiation. Based on the reported decoherence time for this process a coherent control mechanism of the THz radiation is introduced by varying the phase of a second laser.