ON THE INFLUENCE OF DISORDER ON RADIATIVELY COUPLED MULTIPLE-QUANTUM WELLS

A theoretical investigation of the effects of static disorder on the l inear optical response and the degenerate four-wave-mixing signals of multiple quantum well Bragg structures is presented. It is shown that disorder leads to a finite radiative coupling strength of subradiant m odes that are optically forbidden in tl-le ideal structure. In the abs orption spectrum, tile subradiant modes appear as sharp resonances in the presence of barrier thickness fluctuations, wheres the disorder in duced subradiant modes are inhomogeneously broadened in the presence o f interface roughness. The decay of the time integrated four-wave-mixi ng signal at large delays is determined by the dephasing time of subra diant modes, whereas the initial fast decay is dominated by the superr adiant mode. A free induction decay is observed in the presence of bar rier thickness fluctuations. In contrast, even a small inhomogeneous b roadening induces a photon-echo-like behavior for the subradiant modes , while the superradiant mode still exhibits a free induction decay.