Spin diffusion and relaxation measurements by optical sampling four-wave-mixing technique

Summary form only given. In order to investigate the relation between particle diffusion and spin diffusion, we used polarization-dependent transient gratings, an exciton density grating and an exciton spin grating, in optical sampling four-wave mixing measurements (OSFWM), which allows us to measure both particle and spin diffusion in the same system. Because OSFWM has a wide observable temporal range from sub-ps to 13 ns with 200-fs temporal resolution, long recombination is possible to observe, and therefore we can compare directly both diffusions. The sample investigated consists of 25 periods of undoped 68-/spl Aring/-thick GaAs quantum wells (QWs), alternated with 198-/spl Aring/-thick Al/sub 0.3/Ga/sub 0.7/As barrier layers. The sample was grown on a semi-insulating [100]-GaAs substrate by molecular beam epitaxy.