Figure 4.

Photo-excited carrier density dependence of electron spin relaxation times measured at 10 K with excitation wavelength of 798 nm. (a) The typical time-resolved Kerr rotation signals measured at three different pumping electron densities for the asymmetric GaAs QW. (b) Photo-excited carrier density dependence of electron spin relaxation times measured for both symmetric and asymmetric GaAs QW samples. The solid lines are drawn to guide eyes.