Many-body dynamics and energy relaxation times in a wide semiconductor quantum well as probed by nonlinear far-infrared absorption

In quantum wells, absorption between the quantized subbands of the conduction band does not take place at the difference of the subband energies; the interactions of the electrons shift the intersubband absorption to higher frequency; this is called the depolarization shift. This shift can be thought of as a dynamic screening effect, and depends upon the difference in population between the subbands of interest. These are the first group of measurements of the dynamics of the depolarization shift, and they offer the possibility of both increased understanding of many-body interactions in real systems, and the possibility of novel quasi-optical devices operating in the far-infared (FIR)