We have investigated the saturation of intersubband absorption and the intersubband relaxation time in the valence band of Si/SiGe quantum wells. The quantum wells consist of 3 nm thickp‐doped Si0.8Ge0.2layers separated by 20 nm thick silicon barriers. At room temperature, these quantum wells exhibit intersubband absorption inppolarization (component of the electric field parallel to the growth axis), which peaks around 130 meV (≊10 &mgr;m). The saturation of intersubband absorption has been investigated using a picosecond free electron laser by two different techniques. The intersubband absorption is first analyzed as a function of the pump intensity. The saturation is found to occur around 90 MW/cm2, which yields a characteristic lifetime T1≊0.7 ps. In a second set of experiments, the lifetime is determined by time‐resolved pump and probe experiments in cross polarization. The intersubband transition is pumped inppolarization and the saturated absorption is probed with a delayed beam inspolarization. An intersubband lifetime ≊0.4 ps is deduced by this technique. The saturation behavior is analyzed in terms of an inhomogeneously broadened two‐level system. ©1996 American Institute of Physics.