Electron relaxation time measurements in GaAs/AlGaAs quantum wells: Intersubband absorption saturation by a free-electron laser

The intersubband absorption saturation in GaAs/AlGaAs quantum wells as a function of the incident power has been measured, using picosecond micropulses with a power density up to 1 GW/cm2 delivered by a free-electron laser. The absorption in a sample with a bound-to-bound transition was compared to the absorption in a sample with a bound-to-resonant transition, and it was found that the electron relaxation time in the bound-to-bound transition is about four times shorter than for the bound-to-resonant transition.